PSAS/ capstone2009/ design

Battery Sensor Requirements

  • MUST monitor charge ("coulomb counter")
  • MUST measure pack voltage
  • SHOULD: monitor the voltage on each cell
  • MUST monitor battery pack temperature (MUST be compatible with charging chip)
  • SHOULD separate high current connector from sensing connector
  • (Note: The battery pack we use is 4-cells in series and 2-cells in parallel.)

Battery Sensor Research

Initial research into battery sensor IC on Digi-key website shows that there are three companies making the chips: Texas Instruments, Dallas Semiconductor/Maxim-ic, and Microchip Technology. We also looked at Fairchild and Intersil. TI and Microchip technology don't have any chip that monitor a 4-cell Li-ion Battery. The only chip that works with 1-10 cell Li-ion Battery is DS2788 from Maxim. Intersil has three chips that might work for monitoring individual cell voltage, which are ISL9208, ISL9216/9717, and ISL94200. All of them use I2C interface:

  • ISL9208: Supports battery pack configurations consisting of 5-cells to 7-cells in series and 1 or more cells in parallel. This is the final chip that we chose because its application note shows that we can also use this chip for 4-cells battery as well.
  • ISL9216/9217: Provides integrated overcurrent protection circuitry, short circuit protection, an internal voltage regulator, internal cell balancing switches, cell voltage level shifters, and drive circuitry for external FET devices that control pack charge and discharge. The load monitor current is (20,40,60)μA and <10μA sleep mode. We didn't choose this chip because we would need to cascade the ISL9216 and ISL9217 to make it work.
  • ISL94200: We didn't choose this chip because it doesn't have the internal cell balancing switches.

In terms of a fuel gage, we chose the Maxim (was Dallas) DS2788. It's the only fuel gauge chip that made sense, we wish we remember why.

Battery Sensor Design

By using the ISL9208 for charge balancing and voltage level shifting and the DS2788 as a charge counter, we get a two chip solution that meets all of our requirements. The only downside is the DS2788 requires a low side shunt (ugh) and has a one wire bus interface (double ugh: what was Maxim thinking?).

This design is thus pretty chip centric, so we'll go over the design by really going over the chip.

ISL9208 battery charge leveling and cell voltage level shifting

The ISL9208 is almost the perfect chip for us, although it is a bit crusty. Here's an application note that's worth reading about it. A few notes on how we're using it:

  • We're only using it for 4 cell series pack.
  • We don't care about the overcurrent protection (OCP) and the over charge protection. We're completely ignoring this feature and not even connecting the FETs; that's what the fuse and the Avionics Power System (APS) power switches (with integrated circuit breaker) are for.
  • We do care about the internal cell balancing switches, that gives us cell balancing. Yay.
    • 200 mA max balance current, with internal IC power dissipation at 400 mW and internal MOSFETs with 5 +/- 2 ohm Rdson
  • We do care about the voltage monitor level shifters, that allows us to use the APS microcontroller to ADC each cell voltage, despite the pack's high voltage.
  • Internal chip and external battery temperature are also a feature, but we'll get the ext. battery temperature from the DS2788.
  • Has sleep mode, < 10 uA draw, so we should use that for sure when the APS is inactive.
  • We're dubious about the external NPN pass transistor for the 3.3V power supply, but it's so simple it'll probably be OK as long as it doesn't suck too much power. This system will DEFINITELY need to be measured for current consumption.


  • The 15 ohm CBAL resistors will toast the chip; choose a better value
  • The voltage drop across the shunt resistor will affect the analog out voltage measurement. Compensate with known current and thus known voltage drop from the DS2788? What's the max/min voltage drop?
  • Come up with register settings for the LPC ISL.
  • Come up with an automated sleep circuit so that the ISL chip goes to sleep when the LPC is asleep/disconnected.



  • Recalculate Rshunt, which drives much of the problems with this board because the diff between sensor board ground and "pack" ground.


  • Measures voltage, temperature, and current,and estimates available capacity for rechargeable lithium-ion (Li+) and Li+ polymer batteries.

  • Cell characteristics and application parameters used in the calculations are stored in on-chip EEPROM. The available capacity registers report a conservative estimate of the amount of charge that can be removed given the current temperature, discharge rate, stored charge, and application parameters. Capacity estimation is reported in mAh remaining and percentage of full.

  • LED display drivers and a debounced input make display of the capacity information easy. The LED pins can directly sink current, requiring only a resistor for setting the current in the LED display, thus reducing space and cost.

Component Selection


LEDs for Fuel-Gauge Display

D3006-D3009 and R3006,R3017,R3022 and R3023

Protection circuits for the input/output data pins.


Sense resistor for the DS2788. With R3007 = 1mOhm, the current resolution is 1.5626uV/1mOhm = 1.5mA,which is good enough for our test.

The resistor I chose is CSNL10.001FRCT-ND(Digi-Key number).

  • Family Chip Resistor - Surface Mount
  • Series CSNL
  • Resistance In Ohms 0.001
  • Power (Watts) 1.5W
  • Tolerance ±1%
  • Lead Style Surface Mount (SMD - SMT)
  • Case 2010 (5025 metric)
  • Packaging Cut Tape (CT)
  • Composition Current Sense, Metal Foil
  • Temperature Coefficient ±50ppm/°C

Q1,Q2, R3008-R3011, C3001

Q1 is a P-channel FET, and Q2 is a N-channel FET. R3008 and R3009 form a voltage divider circuit to provide the right voltage level for VIN pin. R3010 and R3011 forms another voltage divider to provide the right voltage level for Vds of Q1. Before the start of a voltage conversion, VMA is driven high. Then Q2 turns on. As a result, Q1 turns on. Therefore, VIN (the Voltage sense input) will input the voltage, which is one fourth of the total battery pack voltage. At the end of the conversion cycle, the VMA pin is driven low. Then Q1 and Q2 are both off. As a result, VIN doesn't input any voltage data. VMA is the voltage measure active. The capacitor C3001 is used to stabilize voltage change.


Fuse to protect the circuit when the current is too high. The one I chose is 0456030.ER from Littelfuse Inc. The Digi-Key Part Number is 0456030.ER-ND.

  • Series NANO²® 456
  • Current 30A
  • Voltage - Rated 125V
  • Package / Case 0.397" L x 0.123" W x 0.123" H (10.1mm x 3.12mm x 3.12mm)
  • Fuse Type Fast Acting, Short Time Lag
  • Mounting Type Holder/Surface Mount
  • Other Names 456030.00


Series resistors on each of the cell inputs to reduce the initial current surge through the ISL9208 inputs. From the application node, a series resistance of 15Ohms will add about 1mV of error to the cell voltage reading, which is acceptable.


Sense resistor of ISL9208 to monitor the change and discharge current. From example 1 of the application note, if the desired over-current level = 8A, and desired short circuit current level = 17A, then the ratio = 17/8 = 2.125. From the table 3, the short circuit threshold is 0.2V and the over-current threshold is 0.10V. The value of the sense resistor = 0.1V/8A = 12.5mOhm.

The resistor I chose is ERJ-B1CJR012U-ND(Digit-Key part number).

  • Family Chip Resistor - Surface Mount
  • Series ERJ
  • Resistance In Ohms 0.012
  • Power (Watts) 1W
  • Tolerance ±5%
  • Lead Style Surface Mount (SMD - SMT)
  • Case 2010 (5025 metric)
  • Packaging Tape & Reel (TR)
  • Composition Thick Film
  • Temperature Coefficient ±350ppm/°C

R3018 and TR3001

The fixed resistor and the thermistor forms a voltage divider. The TEMPI pin inputs the voltage across the thermistor to determine the temperature of the cells.Then the TEMPI pin drops below TEMP3V/13, an external over-temperature condition exists. Therefore, the resister value needs to be 12 times as the resistance of the thermistor. Since the thermistor we chose has resistance of 10k at 25 Celsius, the value of R3018 is 120Kohm.

The thermistor I chose is NTCS0805E3103JMT by Vishay/BC Components. The Digi-key part number is BC2292CT-ND.

  • Family Thermistors - NTC
  • Series 2381
  • Resistance in Ohms @ 25°C 10K
  • B25/85 3570K
  • Operating Temperature -40°C ~ 150°C
  • Resistance Tolerance 5%
  • Value Tolerance 3%
  • Power - Max 210m;
  • Mounting Type PCB, Surface Mount
  • Package / Case 0805 (2012 metric)

T1, C3002 and R3019

T1 is an NPN transistor. The RGO pin connects the emitter of T1 and works in conjunction with the RGC pin to provide a regulated 3.3V. The RGC connects to the base of T1 and provides the control signal for the external transistor to provide the 3.3V regulated voltage on the RGO pin. R3019 is a pull-up resistor, and C3002 is used to stable the voltage changes.

R3020 and R3021

These two resistors control the wake-up threshold of the ISL9208. Their values are calculated using the EQ.1 in the application node. If the wake-up threshold is 3.8V, and the maximum voltage of each cell is 5 and we have a four-cell battery, then R2/(R1+R2) < 0.19. Since R1 determines the current consumption of the circuit, first choose the R1 value as the highest value that is reasonable to use. Let R1 = 1.2Mohm, then R2 = 281.5Kohm. Therefore, I chose R2 = 280Kohm.

Posted Mon Jan 26 02:05:08 2009

AV2b Battery Pack

Battery Pack Requirements

  • SHOULD be a 4-series cell Li battery
  • Battery SHOULD cost <500$
  • Overall Battery SHOULD have energy-mass density (100,,)
  • Overall Battery energy-volume density SHOULD be (200,,)
  • Battery capacity SHOULD be (4,8,) AHr (TODO: TBD on new power budget)
  • SHOULD have dimensions less than (,3.0,3.5) inches in the cross sectional plane of the airframe, length (,,10)inches
  • MUST have a fuse in the pack before the lead
  • Total battery "unplugged" leakage MUST be < C/(1,5,) year rate (e.g. ~ 100 uA for 4 AHr)

Predicted power usage:

Module Current (A)
Flight computer 0.516
GPS: 0.242
ATV: 1.546
transitors: 0.003
APS-can node 0.047
IMU: 0.095
TOTAL 2.4494

Battery Pack Info

We're using a 4S2P pack of "AA Portable Power Corp" PL-5467100-2C (2.75,3.7,4.2) V at 4.250 AHr Li-polymer cell.

This gives us a (11.0,14.8,16.8)V at 8.25 AHr battery pack.

Battery Research

Battery Packs

found prior to adjustment to requirements on 1/30/09

model: PQ-1600LP-4S
capacity: 1.6 Ah
weight: 146 grams
dimensions:  3.03 | 1.46 | 1.3002
price: $65.99
distributer: <>

model: LP-TP2000-4SPL
capacity: 2 Ah
weight: 159.9 grams
dimensions: 2.561 | 1.97 | .99
price: $98.99
distributer: <>

found after adjustments in dimensions on 1/30/09

capacity: 4.25 Ah
voltage: 14.8 V
dimensions: 5.83 | 1.85 | 1.22
weight: 402 grams
energy density:  156.47
price $136.25
distributer: <>

Poly Rc
model: PQ-4350XP-4S
capacity: 4.35 Ah
voltage: 14.8 V
dimensions: 6.5 | 1.8 | 1.3
weight: 436 grams
energy density:  147.66
price: $196.99
distributer: <>

Thunder Power
model: TP4600-4SXL 
capacity: 4.6 Ah
voltage: 14.8V
dimensions: 7.6 | 1.81 | .95
weight: 457 grams
energy density: 148.97
price: $161.24
distributer: <>

model: PQ-5350LP-4S
capacity: 5.35 Ah
voltage: 14.8V
dimensions: 5.56 | 1.82 | 1.58 
weight: 469 grams
energy density: 168.83
price: $180.50
distributer: <>


Manufacturer Model Capacity (Ahr) @ rate Voltage X Y Z Weight (g) En. Dens. Cost Distributor
Tenergy 30512 4 15C 3.7 5.30 1.77 0.26 85 $51.99 link
Tenergy 30502 1.25 10C 3.7 2.56 1.38 0.22 28 $19.99 link
Panasonic CGA103450A 1.95 1C 3.7 1.97 1.34 0.42 39 $13.00 link
sanyo UF103450P 1.88 1C 3.7 1.95 1.34 0.37 38.5 180 Wh/kg $18.34 link PL-896474-2C 5 2C 3.7 2.92 2.52 0.35 95 185 Wh/kg $24.95 link PL-875055-2C 2.5 2C 3.7 2.17 1.97 0.34 51 181 Wh/kg $13.95 link PL-9059156-1C 10 1C 3.7 6.15 2.32 0.35 196 204 Wh/kg $32.95 link L-5467100-2C 4.25 2C 3.7 3.94 2.64 0.22 85 185 Wh/kg $19.95 link


456 series
Littelfuse | <> 
Ferraz Shawmut | <>
Posted Mon Jan 26 02:05:08 2009

Requirements for APS State Machine

  • State Machine should have its own task in freertos

    • Listen for critical inputs
    • check current state and data
    • determine whether to change state or remain in current state
  • Current states:

    • Sleep
    • Wake
    • Safe
    • Armed
  • Sub-functions in State Task will perform internal tasks

    APS must have different states

  • Sleep Mode

  • Wake Mode
  • Safe Mode
  • Armed Mode

Sleep Mode

  • Powered off
  • Able to be powered up by remote signal
  • Very low current draw on battery

Wake Mode

  • Powered up
  • Check of systems, environment
  • Initializations

Safe Mode

  • Initialization complete
  • External system communication normal
  • Ready for armed state
  • Physically locked out of armed state by ground pin or other device

Armed Mode

  • Ready for launch
  • Crew safety top priority
    • Keep safety margins
    • All work should be remote

Testing Algorithm for APS State Machine

Pseudocode for rough draft of APS state machine

enum aps_state //easier to use real names when referring to states

  • sleep = 0
  • wake
  • safe
  • armed

variable rocket_mode = sleep //could init into other state if desired

task apssm_task

  • get data from environment checklist

    • change state depending on data //for demo, use buttons

    • if button 1 triggered

      • switch rocket_mode

        • case sleep: rocket_mode++, output new mode to serial

        • case wake: rocket_mode++, output new mode to serial

        • case safe: rocket_mode++, output new mode to serial

        • case armed: rocket_mode = sleep, output new mode to serial

      • end switch

    • if button 2 triggered

      • rocket_mode = sleep //simulate reset sequence

      • output 'reset event' and new mode to serial

  • keep looping apssm_task

Error Handling

  • Error levels
    • Error levels are implemented as a prefix of the error message.
  • Error Logs
    • The error log is held as a global-scope array of plain text, accessible by all tasks
  • Error messages
    • Error messages are in the format [prefix][message][unique detail]
    • Error messages are the responsibility of the function observing the error.
      • Functions must report error messages in the correct format
      • Functions must report error messages 127 characters or less, and end with a string terminator (null byte)

Serial console

  • Request error logs
    • Listens to incoming traffic on UART, on receipt of keyword "errors" responds with a dump of error log
  • Checking registers
    • Stub code in place for this and additional UART command functionality

Battery Management

  • Read battery voltages and currents
  • Pack voltage
  • Cell voltage
  • Charge counting into capture timer (charge, calculate amps = charge/delta_T)
  • Never turned off unless disconnected


  • Monitor shore power
  • Rocket Ready signal, SAFETY CRITICAL
  • Relays will prevent launch if there are problems
  • Any node can give the Scrub Launch signal

Over current monitoring and “circuit breaker” functionality

  • All sensors, power supplies (pyro, sps, etc.), communication checks needed before cleared for launch
Posted Mon Jan 26 02:05:08 2009


* MUST meet standard lithium charge/discharge safety requirements (thermal, voltage, current, time, fuse)
* MUST be able to charge at (,1C,C/2) rates at internal air temperature of 50 deg C.
* MAY equalize cells up to some small bypass power (e.g., .5W)
* MUST indicate charging status (on/off)
* MAY indicate some kind of charge % (blink rate, color, LED bar graph, etc)

Internal Charger

Final IC Chosen:

Model : LTC 4007

  • Manufacturer: Linear
  • Charge Rate: 4A
  • Datasheet: LT4007

ICs Not Chosen:

Model: MAX8731A

  • Manufacturer: MAXIM
  • Charge Rate: 8A
  • Datasheet: MAX87318

Model: LTC1759

  • Manufacturer: Linear
  • Charge Rate: 8A
  • Datasheet: LTC1759

Model: BQ24705

  • Manufacturer: Texas Instruments
  • Charge Rate: 8A
  • Efficiency: >95%
  • Datasheet: BQ24705

Model: ISL88731A

  • Manufacturer: Intersil
  • Charge Rate: 8A
  • Datasheet: ISL88731A

Model: BQ24751A

  • Manufacturer: Texas Instruments
  • Charge Rate: 10A
  • Efficiency: >95%
  • Datasheet: BQ24751A

Model: BQ24730

  • Manufacturer: Texas Instruments
  • Charge Rate: 20A
  • Datasheet: BQ24730

Model: MAX17005/6/15

  • Manufacturer: Maxim
  • Charge Rate: 5A
  • Datasheet: MAX17005

Model: MAX1909/MAX8725

  • Manufacturer: Maxim
  • Charge Rate: >4A
  • Efficiency: >95%
  • Datasheet: MAX1909/8725


Icharge(max)= ((Vref * 3.01kΩ)/Rprog)-.035V)/Rsense)

Assuming Rprog = 26.7 kΩ, based on needs for C/10 comparator Vref = 1.19 V
Rprog and Vref values from datasheet

Charge is 8.5 A

solving for Rsense we get: Rsense=(1.19V * 3.01kΩ)/26.7kΩ)-.035V)/8.5A) = .15Ω

Parts List

LTC4007 4A Charger

U2101 LTC4357

R2100 Low-pass Resistor used to prevent DC overshoot. Value: 10Ω Value based on previous design calculations. Given we are using the same charger chip; keeping the same value seemed reasonable.

R2101 Referred to Rsense in LTC4007 datasheet Value 1 mΩ Using equation of I2R = P, 8.52(.001) = .07225

R2102,2103 Value: 3.01k Based on LTC4007 datasheet values

R2104,2105,2106,2107,2108,2109,2110 Value: 47k Based on need for PIC in previous design

R2111,2112 The two components added together equal Rprog in LTC4007 datasheet Value: 82.5k Using equation for Rprog, got 82.343k total, previois design had 30.1k and 51.1k, which equals 81.2k , which is close so will add .5k to each to get within range, thus 30.6k and 51.6k respectively.

R2113 Value: 6.04k Based on LTC4007 datasheet

R2114 Value: 309k Using equation found in Rt pin description, gives 2.006 hours timer period, 308k better, but not a standard value.

R2115 Value: 5k Based on value in datasheet, used to calculate Rcl

R2116 Value : .168 ohms Based on 8.5 A current, and equation found in Adaptor limiting section

R2117 Value: 11.8k Located before thermistor

R2118 Value: 13.5k Located in parallel with thermistor

R2119 Value 10k

C2100 Bypass capacitor Value: 15 nF Within range given on ltc4007 charger data sheet

C2101 Value:.12uF Based on value given in ltc4007 charger datasheet

C2102 Value: .0047uF Based on values in LTC charger datasheet

C2103,2104 Value: 20uF Based on values in LTC Charger datasheet diagram

C2105 Value .1uF Based on Value in LTC charger datasheet

C2106 Value: 1.2uF Used equations related to thermistor, found in ltc4007 datasheet, calculated at 1.186 uF Digikey number: 399-3119-2-ND

C2107 Value: 39u Battery board C2108 Value: .1u

C2109 100nF

Q2100 N channel mosfet Model #: STS17NH3LL Operates RDS 50 mOhms at 8.5A

Q2101,2102 P channel mosfet Model# : FQB17P06 Operates 120 mOhms at 8.5A

Q2103 N channel mosfet Model#: STS17NH3LL Operates RDS 50 mOhms at 8.5A Previous model only operated at 4.5A


D2100 Model: MA2Q705 Based on previous charger circuit design


L2100 Value 10uH Calculated value less than 10uH not recommended in ltc4007 datasheet, but calculated value was.

External Charger

Near end of project the PSAS decided to look into using an external charger given the capabilities of the charger that they had selected, and space on the board.

Looking at power switches and the internal charger design saw use for switch controller and mosfet as they had the range needed, and by using the enable pin to switch, could control via the microcontroller.

Parts Q2114,2115,2116 See Q2104 for specs Used to control flow based on microcontroller signal 2115,2116 used for loads

C2117,2118,2119 See C2107 for details

U2111,2112,2113 See U2101 for specifics Used to control flow based on microcontroller signal

Posted Mon Jan 26 02:05:08 2009

USB Hub Requirements:

  • SHOULD be USB 2.0 compliant High Speed (480 Mbps)
  • MUST handle (8,,) downstream devices (devices may be further hubs)
  • SHOULD have hub status LEDs

USB HUB IC chosen: SMSC USB2517


SMSC-USB2517 Datasheet

Evaluation-Board User Manual:

SMSC-USB2517 Eval Board

Evaluation-Board Schematic (for reference design):

SMSC-USB2517 Eval Board Schematic

Other Miscelaneous Reference Material:

SMSC-USB2517 Misc.

USB 2.0 Specification

USB2517 Basic Functional Description:

  • The SMSC-USB2517 hub controller comes in a 64 pin, 9x9mm QFN package. It is an OEM (Original Equipment Manufacturer) configurable integrated circuit which uses a multi-transaction translator (MTT) and is capable of supporting 7 downstream ports. The hub supports low, full and high speed devices on all of the enabled ports.

  • All required resistors on the downstream ports are integrated into the hub. This includes all series termination resistors on D+ and D- pins and all required pull-up and pull-down resistors on D+ and D- pins. The over-current sense pins for the downstream ports have internal pull-up resistors as well.

  • Some key features of the USB2517 include:

    • low power dissipation, high performance, small footprint
    • Fully compliant with USB 2.0 specification
    • 3 options for hub configurations: I2C (via EEPROM), SMBus, and internal default configurations via strapping options
  • The USB2517 also offers a PortMap flexible port mapping ability, PortSwap which allows programming of USB differential pair pin locations, and PhyBoost which provides programmable USB signal drive strength.

  • For more information about these options follow link to datasheet.

USB Hub Circuit Design:

Pin Connections (For detailed pin descriptions see table 5.2 in USB2517 datasheet)


  • These pins provide one of the two differential USB data signals to downstream ports 1-7
  • each of these pins is connected to the pair of the USB_L pins of the respective power switch port connector
  • Pulling any of these pins, along with the associated USBDP pin, up to 3.3V with a 10kOhm resistor disables the respective port
  • Instead of pullup to 3.3V, we will connect these pins to the ARM giving it control of what ports are enabled


  • This pins proved the other of the two differential USB data signals to downstream ports 1-7
  • Each of these pins is connected to the pair of USB_H pins of the respective power switch port connector
  • Pulling any of these pins, along with the associated USBDM pin, up to 3.3V with a 10kOhm resistor disables the respective port
  • Instead of pullup to 3.3V, we will connect these pins to the ARM giving it control of what ports are enabled


  • There are a total of 7 of these pins, each connected to +3.3V


  • These pins connect to LEDs which are used to indicate both connection status and port speed for each of teh 7 ports.
  • This is done with a combination of a red and a green LED assigned to each port.
  • See section 6.1.2 on page 29 of the USB2517 datasheet for more information
  • Also see LEDs in the component selection

  • These pins also are used to configure the portswapping option, which we are not using. To ensure port polarity swapping does not inadvertently occur, these pins must be low when RESET_N is asserted.


  • These pins connect to amber LEDs which indiccate overcurrent conditions on downstream ports
  • We are not using overcurrent sensing so these pins are not connected


  • These multifunction pins can connect to amber LEDs which indicate overcurrent conditions on downstream ports
  • They are also sampled after RESET_N is asserted to determine the signal strength of the USB differential signals to downstream ports as follows:

    • BOOST[1:0] = '00': Normal signal strength
    • BOOST[1:0] = '01': approximate 4% signal boost
    • BOOST[1:0] = '10': approximate 8% signal boost
    • BOOST[1:0] = '11': approximate 12% signal boost
  • In my current design, the signal strength is set at normal strength so these pins are strapped to ground. However these pins could be connected to the ARM so that signal strength can becontrolled on-line


  • Overcurrent sense input pins. We are not using overcurrent sensing function of hub. Since these pins are pulled up internally, they are treated as no connects.


  • These pins provide power to downstream ports.
  • We are using a seperate power switch network so this pins are treated as no-connects


  • Used by the manufacturer for IC testing. Must be connected to ground


  • VDD core regulator filter capacitor.
  • Datasheet states this pin must be connected to ground through a 0.1uF capacitor


  • This active low pin resets the USB2517 after it is asserted for 1us
  • After this pin is asserted, the configuration pins are sampled to determine how the hub is configured
  • This pin is pulled up to 3.3V with a 10kOhm resistor and will also connect to the ARM so that configuration can be done on-line


  • Detects upstream VBUS power
  • The dtasheet states that in self powered applications, which ours is, this pin must be tied to 3.3V



    • As I understand the datasheet, this function of the pin supports an LED which indicates whether the USB is configured.
    • If asserted, the hub is configured and USB is active
    • If negated, hub is unconfigured or configured and in USB suspend
    • The active state of the LED is determined by the values of NON-REM[0] and NON-REM[1] (see below)

    • Detects availability of local power source
    • Low = Self/local power source is NOT available (Hub is powered only with VBUS power)
    • High = Self/local power source is available
  • NON-REM[0]

    • This is a configuration strap option
    • For this function, this pin along with NON-REM[1] is sampled at assertion of RESET-N to determine which, if any, of the downstream devices are removeable
    • Which ports are removeable is determined as follows using NON-REM[0] and NON-REM[1]:
      • NON-REM[1:0] = '00': All ports removeable, Suspend indicator LED active high
      • NON-REM[1:0] = '01': Port 1 is non-removeable, Suspend indicator LED active low
      • NON-REM[1:0] = '10': Ports 1 and 2 are non-removeable and LED is active high
      • NON-REM[1:0] = '11': Ports 1, 2 and 3 are non-removeable and LED active low
  • LOCAL-PWR and NON-REM[0] seem to be contradictory for our purposes. At this point I have this pin permanently tied to ground along with NON-REM[1] so that the hub is permanently configured for removeable devices on all ports. However doing this would then tell the hub that self/local power is NOT available. My thought is that this pin will need a weak pullup and also be connected to the ARM which can drive the pin low at assertion of RESET-N. This way, the hub will be configured with all removeable devices and still detect local power, which is all we are using.


  • Another multifunction pin used for hub configuration

  • SDA

    • Serial data signal

    • Server message block data signal
  • NON-REM[1]

    • Used in conjunction with NON-REM[0] to determine which, if any devices attached to the downstream ports are removeable. See NON-REM[0] description for explanation


  • A multifunction pin used in hub configuration

  • SCL

    • Serial clock signal

    • System management bus clock signal
  • CFG-SEL[0]

    • Sampled at RESET-N assertion in conjunction with CFG-SEL[1] and CFG-SEL[2] to determine which internal default configuration of the hub is used. See CFG-SEL[2] description for further explanation of these options
  • I am assuming that we are not using a serial clock signal or system management bus clock so these signals are not used in the hub circuit at this time


  • Another multifunction pin used in hub configuration

  • HS-IND:

    • The pin can support an LED which indicates whether the hub is connected at high speed
    • Asserted = hub connected at high speed
    • Negated = hub is connected at full speed
  • CFG-SEL[1]

    • Sampled at RESET-N assertion in conjunction with CFG-SEL[0] and CFG-SEL[2] to determine which internal default configuration of the hub is used. See CFG-SEL[2] description for further explanation of these options
    • If CFG-SEL[1] = '0': HS-IND is active high
    • If CFG-SEL[1] = '1': HS-IND is active low


  • Sampled at RESET-N assertion in conjunction with CFG-SEL[0] and CFG-SEL[1] to determine which internal default configuration of the hub is used.

  • See table 8.2 on pages 33 and 34 of USB2517 datasheet for the different default configuration options which can be set using CFG-SEL[2:0]

  • For our design CFG-SEL[2:0] = '000' which means the following:

    • Strap options enabled
    • Self-power option enabled
    • LED mode = speed
    • Individual power switching
    • individual over-current sensing


  • One of 2 signals of the differential USB data signal from an upstream device
  • This pin is connected to the USB-H pins on the connector to the flight computer (J2007)


  • The second signal of the differential USB data signal from an upstream device
  • This pin is connected to the USB-L pins on the connector to the flight computer (J2007)


  • Connects to one terminal of the 24MHz external crystal


  • Connects to the other terminal of the external 24MHz crystal


  • PLL regulator filter capacitor
  • As the datasheet directs, this pin is connected to ground through a 1.0uF capacitor


  • This pin sets the USB tranceiver bias
  • As the datasheet directs, this pin connects to a 12kOhm resistor to ground (R2065)

Component Selection:

Integrated Circuits:


  • SMSC_USB2517 USB hub chip
  • See above for explanations



  • 1MOhm filter resistor for external clock
  • This resistor was included in the circuit based on the smsc reference design. Not sure if this is needed


  • 12kOhm bias resistor sets the internal bias of the hub chip
  • 2517 datasheet specifies this value of resistor on RBIAS pin
  • See RBIAS pin description for more information


  • 10kOhm pullup resistor connected to the RESET-N pin
  • This pullup to 3.3V ensures the USB hub reset function is negated unless asserted by the ARM


  • 10kOhm pulldown resistors for CFG-SEL[2:0] pins
  • This ensures that the default configuration scheme of the usb hub will be CFG-SEL[2:0] = '000'
  • See CFG-SEL[2] pin description for explanation of settings associated with this configuration
  • These pins are also connected to GPIO pins of the ARM so that the HUB can be re-configured by the micro-controller if so desired

R2070, R2071

  • These resistors are attached to multifunctional pins on the hub
  • R2070 is a 10kOhm pull-down resistor ensuring that NON-REM[1] has a default logic low level (We are not using the other functions associated with this pin. This pin is also conected to a GPIO of the ARM so that other options can be used if needed
  • R2071 is a 10kOhm pull-up resistor to ensure that SUSP-IND/LOCAL-PWR/NON-REM[0] pin has a default logic high level

    • In the event that the HUB is reset, this pin will generally need to be driven low by the ARM along with NON_REM[1] to ensure that all 7 of the HUB's downstream ports are configured to support removeable devices. This configuration can be changed if need be as both pins are connected to GPIO pins of the ARM
    • The pull-up is necessary because of the fact that a logic high is needed on this pin to tell the HUB that a local power source is present. If this is not a logic high, the HUB will think that all power is provided from the VBUS which we do not implement
    • If the ARM should fail to drive this pin low upon a reset, port 1 will be considered a non-removeable port. This should not pose too much of a problem as the hub can be re-configured at any time.

R2072, R2073

  • 10kOhm pull-down resistors connected to the BOOST[1:0] pins
  • The pull-downs ensure that the default setting of the HUB's signal strength for downstream ports will be 'no-boost'
  • These pins also connect to GPIO pins of the ARM so that the HUB can be reconfigured for signal boost if needed
  • See BOOST[1:0] pin descriptions for more information


  • 330 Ohm current limiting resistors to protect the LED port status indicators
  • This value is questionable as the design uses 0605 LEDs and I'm not sure if such a small resistor provides enough protection.



  • 33pF bypass capacitors connected to the terminals of the external 24MHz clock
  • These values were chosen based on the 2517 datasheet reference design


  • 1uF capacitor connected from PLLFILT pin to ground, acts as a filter capacitor for the HUB's internal PLL
  • This capacitor value is specified in the datasheet


  • 0.1uF VDD core regulator filter capacitor, connectes from CRFILT pin to ground
  • This value is specified in the 2517 datasheet


  • 0.1uF bypass capacitors to filter high frequency noise on the 7 VDD pins



  • Green LED status indicators indicating the status of the 7 downstream ports
  • These indicators provide downstream port connection status and work in conjunction with red LEDs (LED2015-LED2021) to indicate connection speed
  • See LED2015-LED2021 description for more information about connection speed indication, also see section 6.1 in 2517 datasheet for detailed description of LED functionality
  • The green status LEDs function in accordance with section 11.5.3 of USB 2.0 specification


  • Red LEDs which work in conjunction with green LEDs (LED2008-LED2014) to indicate speed of the devices attached to the 7 downstream ports
  • These and the green LEDs are connected to the LED-A-N[7:1] pins in such a way that they function as follows:
    • When any of the pins is driven to a logic low, the corresponding green LED will light up which indicates that a lowspeed device is attached to the respective port
    • When any of the pins is driven to a logic high, the corresponding red LED will light up indicating that a full speed device is attached to the respective port
    • When any of the pins outputs a 1kHz square wave, both LEDs will be pulsed on and off. The datasheet notes that the green/red LEDs should be in a single package so that this condition will result in an orange color, however we are using seperate 0605 LEDs so it will simply appear as both the red and green LEDs are on. This indicates that a high speed device is attached to the respective downstream port
    • When nothing is driven out on an LED-A-N pin, the pin floats to a "tri-state" condition and neither of the LEDs light up. This indicates that the respective port is either disabled or nothing is attached



  • This diode ensures that when any of the LED-A-N pins float to a tri-state condition, the LEDs do not light up, correctly inicating the respective downstream is disabled or nothing is connected



  • External 24MHz external crystal which provides the clock signal to the USB hub

Posted Mon Jan 26 02:05:08 2009


  • MUST seamlessly shift between shore power and battery power
  • MUST be able to detect the presence of shore power
  • MUST wake up APS microcontroller if shore power turned on
  • MUST be able to sense if connector is inserted or removed (launch detect)

Some Design Considerations:

  • If we are using the LTC4007 for the charger chip, we require an Ideal_Diode

    • This is essentially a FET with a controller
    • FET requires very low Rds_on since it is in the main power path
    • Controller must meet thermal requirements so as not to cook the power path controller during operation
    • Also needs to handle all stresses that may be encountered during operation

Ideal Diode Transistors:

  • After discussing with Andrew and Tim, the Si4422DY will measure up to our requirements:


  • Datasheet: Si4422DY
  • Rds_on = 4.5mOhm
  • If we design for 10A
    • P = I^2R = 100 x 4.5x10^-3 = 0.45W

Ideal Dioide Controllers:

  • Need to handle 30+Volts
  • 10A current capability
  • fast switching

LTC4357 (Chosen)

  • Datasheet: LTC4357
  • V range = 9-80V
  • Operating current capability 20A
  • t-off = 300-500ns
  • DFN Package

LTC4412 (In use on current APS)

  • Datasheet: LTC4412
  • V range = 2.5-28V
  • Current Capability 5A (Not enough)


  • More "rugged" version of the LTC4412
  • has a larger max Vin, but still suffers from the 5A current limitation
  • Datasheet: LTC4412HV


  • As can be seen in the LTC4357 datasheet, the IC's IN pin connects to the source of the FET. The source then becomes the anode of the ideal diode. The OUT pin connects to the FET's drain which acts as the ideal diode's cathode. The LTC4357 then detects the voltages at each pin and the gate pin then drives the gate of the FET to maintain the forward drop at 25mV. If the voltage accross IN to OUT becomes more negative than -25mV, the gate of the FET is pulled low with a strong pull down. This would occur in the event that shore power is present.

Component Selection:

Integrated Circuits:


  • Ideal diode controller. See above for functionality



  • Functions as the ideal diode. See above for functionality



  • 10kOhm Pull down for launch detect



  • 39uF bypass capacitor. This value is recommended in the datasheet

C2108, C2109

  • 100nF bypass capacitors



  • Shore power connector. Will be updated when Dave has an actual connector. As it stands now this is just an arbitrary 5-pin connector with the followibng connections:

    • RCKT_RDY

      • Connects to the ARM which provides the flight computer with the signal indicating the rocket is ready for launch
    • SH_TX

      • Transmit signal from shore power, this signal will connect to RX of the ARM. In the event of launch, the shore power umbilical will pull out of the connector and this signal will be pulled low by R2119 indicating to the ARM that launch has occurred.
    • SH_RX

      • Recieve signal to shore power, connects to TX of ARM
    • SH_GND

      • Shore power ground
    • SH_POWER

      • Main power from umbilical
Posted Mon Jan 26 02:05:08 2009


The specifications the APS power switches are required to meet are as follows:

  • Power Switches
    • MUST have (8,,) independent resettable electronic circuit breakers with adjustable current trip and trip delay. Setting can be via resistor strap, EEPROM, etc. Current trip should be latch-off or selectable.
    • MUST have Soft on/off feature
    • MUST have no mechanical switches in main power path.
    • MUST indicate power switch on/off state (LED for human, and electrical signal for APS node)
    • MAY indicate power switch fault state
    • MUST operate continuously within 20% of the over-current set point
    • MUST allow set currents in the range (0.1, 5)A
    • MUST allow over current transients of 100% for minimum 100 ms without fault to the load

Chosen Integrated Circuits:

  • The design of the APS power switches will be similar to those used in the LV2b APS in that they will each consist of an external FET combined with a controller IC. This is mainly because of the fact that this form of switch is very robust and reliable and still offers a great deal of control over the various parameters in order to meet the specs. Aside from the ability to meet above specs, some major considerations when choosing components were:

  • Larger supply voltage (designing for 20V or greater, max for old controller was 18V)

  • High side switch (reacts to fault at high rather than low side of switch)
  • Require FET which has a low Rds-on which is ideal in that we want the FET to resemble a wire as closely as possible when on
  • Simpler design requiring less external components

Switch Controller IC (TPS2490)

  • The IC chosen as the controller is the TPS2490 Postitive High-Voltge Power-Limiting Hotswap Controller by Texas Instruments. Click below to view this item's datasheet.

Controller Datasheet

TPS2490 datasheet

Initial reasons for choosing TPS2490:

  • Wide operating voltage (+9V to +80)
  • Under voltage lockout feature
  • Simpler reference design than LTC1154 (used on LV2b APS)
  • MSOP package
  • Programmable fault timer
  • Programmable power limit to limit dissipation in FET

N-Channel MOSFET transistor (Si4122DY)

  • The transistor choice was based on a large Vds range, small Rds-on, and relatively small package size. The FET chosen is the Vishay Si4122DY N-channel MOSFET which is rated at a max Vds of 40V and and Rds-on of 4.5mOhm at a Vgs of 10V.

FET Datasheet

Si4122DY datasheet

Power Switch Design

TPS2490 Pin Descriptions:

  • The following pin descriptions were taken from the datasheet. For a more in depth description, see pages 9 and 10.


This pin serves 3 functions (See Function Descriptions for explanations of specific functions):

  1. biasing power to the controller IC
  2. Input to power on reset (POR) and under voltage lockout functions (UVLO)
  3. Voltage sense at one of the terminals of sense resistor Rs (See Typical Application diagram on page 1 of datasheet)


Connects to downstream terminal of sense resistor Rs. This pin monitors the voltage at the FET drain (refered to as M1 in datasheet) and Rs terminal to provide feedback to the controller's constant power limiting engine (see Function Descriptions) as to M1 current (Id) and voltage (Vds). Id is calculated using voltage difference between VCC and SENSE pins divided by the value of sense resistor Rs. Vds is calculated with the difference between voltages on SENSE and OUT pins.


Provides the high side gate drive for the FET M1. This pin is controlled by the internal gate drive amplifier which provides a pullup of 22uA from an internal charge pump and a strong pulldown to ground of 75mA. Pull-down current is a non-linear function of the amplifier overdrive providing small overdrive for small overloads, and large overdrive fro fast reaction to output shorts. This pin also employs a seperate 2mA pull-down to shut off transistor M1 when voltage on EN pin, or UVLO conditions cause this to happen.


This pin is used by the constant power engine and PG comparator to measure Vds of M1 transistor. Internal protection circuits leak a small current from this pin when it is low.


The TPS2490 gate drive is enabled if the positive threshold is exceeded and internal POR and UVLO thresholds have been satisfied. If the IC is latched off, it can be reset by cycling the EN pin below the negative threshold and then back high. The voltage thresholds for this pin are as follows:

  • V-EN-High: typical 1.35V
  • V-EN-Low: typical 1.25V


Provides a 4V reference voltage for use in setting the voltage on the PROG pin. This voltage is available once the POR and UVLO thresholds have been satisfied. This pin supplies no more than 1mA of current.


The voltage applied to this pin programs the power limit used by the constant power engine. The voltage on this pin is set using a resistor divider circuit on the VREF pin.


An integrating capacitor, Ct in reference design, connected to this pin provides a timing function that controlls the fault time. The TIMER pin charges the capacitor with a 25uA current whenever the TPS2490 is in power limit or current limit, and discharges at 2.5uA otherwise. If the voltage on the TIMER pin reaches 4V, the controller pulls the gate to ground, latches off, and discharges capacitor Ct.


This open-drain output is intended to interface to downstream dc/dc converters or monitoring circuits. PG pin goes open drain (high-voltage with pull-up) after Vds of FET M1 has fallen to about 1.25V and a 9ms deglitch time has passed. PG is false (low) when EN is false, Vds is above 2.5V, or UVLO is active.


This pin is connected to system ground

TPS2490 Functional Descriptions:

APS Power Switch Basic Functional Description

The power switch network employed on the LV2c APS node consists of 7 power switches which provide overcurrent protection for 7 downstream devices. An 8th switch is also employed which provides the same protection for the upstream flight computer. Under normal operation the external N-Channel MOSFET is turned on via the TPS2490 gate drive and power is supplied to peripheral devices through a 16 pin connector. The remaining pins on the connector are used for differential USB and CAN data signals as well as auxilliary pins for direct board to board connections. Each switch is designed for a maximum current limit of 5A along with an allowable 100% (10A) inrush limit which the switch will allow for 100ms without fault to the attached device. Each switch uses a logic enable which is connected to the ARM micro-controller to give full control over which devices are powered. The PG (power good) pin of each switch is also connected to the ARM to indicate the on/off status of each switch.

Under Voltage Lockout (UVLO)

This function will disable the switches in the event of a hard short on the main power path. The switches will latch off if the voltage on VCC reaches or falls below 8.3V.

Constant Power Engine

This function monitors the power dissipation in the external MOSFET for the main purpose of limiting rise in the junction temperature of the FET. Thermal ratings of the FET are used to determine the value of maximum power dissipation allowable. From the datasheet description, this function generally applies to startup conditions as this is when the FET will experience inrush over-currents and run the risk of exceeding its physical limitations. This, in turn, can result in not only damage or destruction of the FET, but damage or destruction of the attached device as well. The constant power engine varies the transistor current, Id, as the voltage, Vds, changes in order to ensure that power dissipation remains constant at the programmed value. As stated, the actual power limit value is determined using thermal parameters of the FET used in the design in the following equation:

Plim <= 0.7 x (Tjmax2 - [(I^2max x Rdson x Rthca) + Tamax])/Rthjc


  • Rthjc = FET junction to case thermal resistance (42 degC/W)
  • Tjmax2 = short term max die temp. of FET, can be set at 150C if max rating is 175C, since Si4122DY max is 150C, we'll set this to 150C - 25C = 125C
  • Rdson is the FET ds on resistance at max operating temp. of about 80C. This value is 4.5mOhm
  • 0.7 represents the tolerance of the constant power engine
  • Rthca = the max case to ambient thermal resistance; equal to Rthja - Rthjc = 21degC/W
  • I^2max = the square of the max drain current, Id, allowed (5A) = 25
  • Tamax = maximum ambient temperature (assuming around 70C)

Using the above equation and the given values:

Plim <= 1.755W

This value can then be programmed into the TPS2490 by applying the voltage to PROG pin which satisfies the following equation given in the datasheet:

VPROG = Plim/(10xIlim)

This equation is derived from the fact that the constant power engine has an output clamped to 50mV according to:


Solving for VPROG:

VPROG = 0.05V x [2x(VSENSE-VOUT)] = 0.1 x (VSENSE - VOUT)

Since Plim = Ilim x Vds = Ilim x (VSENSE - VOUT):

VPROG = [0.1 x Ilim x (VSENSE - VOUT)]/Ilim = Plim/(10xIlim)

The calculated VPROG is applied to the PROG pin using a resistor divider circuit in conjunction with VREF. See conponent selection for resistor values and calculations.

At startup we can assume that Vds = VCC. The initial current through the FET, Id-allowed, is then determined by the set power limit according to:

Id-allowed = Plim/VCC

After stepping to this initial value of Id-allowed, Vds falls and Id is allowed to increase in such a way as to ensure that Plim remains constant. This happens because the power limiting engine adjusts the current limit reference to the gate amplifier thus controlling the transition of the FET from off to fully on, and allowing the transients to pass before it reaches the fully-on state. In non-startup overcurrent conditions, power limiting is assumed to be achieved in a similar fashion. In this situation the volatge at VSENSE will increase due to the rise in current through sense resistor Rs and Id-allowed will be adjusted to ensure that the power dissipation remains constant according to the set limit.

TIMER Operation

In the event that the power limiting engine is activated, a 25uA current is supplied be the TIMER pin to charge the capacitor Ct. Once the capacitor's charge reaches 4V, the FET is turned off and the TPS2490 latches off. The switch then must be reset by cycling the EN pin. See C2000 - C2007 in the component selection for calculation of the capacitor values.


In the description of the constant power limiting engine, it is mentioned that at startup there is a small stepup in Id-allowed to satisfy the power limiting engine. This initial step up in current could pose a potential problem depending on its magnitude. As such, the switch can be designed with a capacitor added to the PROG pin to employ a soft-start function which converts this step into a ramp. The value of the capacitor would then determine the slope of teh ramp. See C2008-C2015 in component selection for more info.

dV/dt Control

The TPS2490 provides the option of dV/dt control in applications which require constant turn on currents for the FET. This is achieved through the addition of a resistor in series with a capacitor connected from the GATE pin to ground. See C2016-C2023 and R2048-R2055 in component selection.

APS Power-Switch Component Selection

Integrated Circuits:

U2000 - U2007

  • Texas Instruments TPS2490 Positive High-Voltage Power-Limiting Hotswap Controller
  • This IC acts as the controller which determines whether or not the external FET is on/off based on several parameters. See above for in depth description of IC functions


Q2000 - Q2007

  • Vishay Si4122DY N-Channel MOSFET
  • These transistors are used in conjunction with the TPS2490 as described above


J2000 - J2007

  • Modified JST-16PS-JED 16-pin Connector.
  • These connectors are used to connect the 7 downstream devices and Flight-Computer to the power switches. The connectors are modified in that they have added "blocks" which allow the plugs from the external devices to be screwed into place, similar to the connection between monitor and computer of a desktop unit
  • The pins of each connector are doubled up for redundancy and pin descriptions for each connector are as follows:
    • 2 pins - positive battery power/shore power, connected to the output of the FET on each switch
    • 2 pins - battery ground/shore ground
    • 2 pins - CAN-H; high level of differential CAN data signal
    • 2 pins - CAN-L; low level of differential CAN data signal
    • 2 pins - USB-H; high level of differential USB data signal
    • 2 pins - USB-L; low level of differential USB data signal
    • 2 pins - AUX-1; available for optional board to board connections
    • 2 pins - AUX-2; available for optional board to board connections


LED2000 - LED2007

  • Green LEDs, 0805 package, used to indicate on/off state of the power switches


R2000 - R2007

  • These resistors are the sense resistors (Rs as refered to in datasheet) used to set the current limit, Ilim, allowed through the FET

  • VCC and SENSE pins are connected to the terminals of these resistors and the TPS2490 computes the voltage VCC - VSENSE. This voltage drop is compared internally to a 50mV threshold voltage via an internal comparator. If the voltage exceeds the 50mV threshold, an overcurrent condition exists and the TPS2490 begins limiting action.

  • The value of these resistors is calculated as follows:

    R = 0.05V/(1.2 x Ilim)

    Where the factor of 1.2 ensures a 20% operating current tolerance

  • With Ilim = 5A:

R = 0.05V/(1.2 x 5) = 8.33mOhm

R2008 - R2015

  • Gate resistors used to minimize noize on the gate drive of each switch
  • It is recommended in the TPS2490 datasheet that if Ciss of the MOSFET > 200pF, a 10 Ohm resistor should be used, otherwise this should be 33Ohm
  • Ciss of the Si4122DY = 4200pF so these resistors will be 10 Ohm

R2016 - R2023

  • The top resistor in the resistor divider circuit used in conjuction with the 4V reference voltage at VREF to set the voltage on the PROG pin and thus program the power limit for the constant power engine.
  • Datasheet notes this resistor can be 4kOhm or greater but it is recommended that 10kOhm or greater be used so these resistors will be 10kOhm

R2024 - R2031

  • The bottom resistor for the voltage divider circuit used in conjunction with the 4V reference voltage ate VREF to set the voltage on the PROG pin and program the power limit for the constant power engine
  • With the power limit, Plim, already calculated to be 1.755W (see constant power limit engine description) the voltage needed at PROG pin can be calculated:

Vprog = Plim/(10 x Ilim,max) = 1.755/(10 x (1.2x5)) = 0.02925V

  • With the top resistor value set at 10kOhm, the value of these resistors can be calculated by solving the following equation for R:

Vprog = Vref(R/(10k + R))

  • Solving for R we obtain:

R = 73.664Ohm

  • If we set these resistors at 75Ohm, Vprog becomes 0.02977V making Plim 1.79W which is an increase of only about 0.04W and doesn't seem as though it would present a problem

R2032 - R2039

  • 10kOhm pull down resistors for the logic enable function of TPS2490
  • In the event that the micro-controller malfunctions or for some reason does not turn on the TPS2490, this pull down ensures that the switch will be latched off

R2040 - R2047

  • 10kOhm pullup resistors for the power good (PG) pin.
  • Since PG is open - drain when 'true', the pullup ensures that PG goes high after Vds falls below 1.25V and a 9ms deglitch time has elapsed

R2048 - R2055

  • These resistors are place holders in case the dV/dt control function is needed. At this point they are not placed

R2056 - R2063

  • These resistors are current limit resistors to ensure LEDs don't burn up during operation.
  • 5kOhm seems to be a reasonable value


C2000 - C2007

  • Timeout capacitors connected to the TIMER pin of the TPS2490 (Ct in the datasheet)
  • These capacitors control the amount of time a fault is allowed before latch off
  • The spec calls for a 100ms time delay
  • It is given that during a fault, this capacitor is charged to 4V with a 25uA current before latch-off occurs, thus we can solve for the capacitor values as follows:

I = C(dV/dt)

  • Where:

I = 25uA

dV/dt = 4V/100ms

  • Thus:

C = I/(dV/dt) = 25uA/(4V/100ms) = 0.625uF

C2008 - C2015

  • These capacitors are placeholders in case the soft start function is required (see function descriptions above)
  • In this design, soft-start is not used so these capacitors are not placed

C2016 - C2023

  • These capacitors are placeholders in the case that the optional dV/dt function is needed (see function description above)
  • In this design we are not using the dV/dt function so these capacitors are not placed

C2024 - C2031

  • 0.1uF bypass capacitors which act to eliminate high frequency glitches on VCC pin of TPS2490

C2032, C2033

  • 0.1uF bypass capacitors to eliminate high frequency glitches between main power and main ground

C2044 - C2051

  • 0.1uF ESD protection capacitors for the 16 pin connectors
Posted Mon Jan 26 02:05:08 2009

future spec

Posted Mon Jan 26 02:05:08 2009
Posted Mon Jan 26 02:05:08 2009

future spec

Posted Mon Jan 26 02:05:08 2009

future spec

Posted Mon Jan 26 02:05:08 2009

future spec

Posted Mon Jan 26 02:05:08 2009

future spec

Posted Mon Jan 26 02:05:08 2009

future spec

Posted Mon Jan 26 02:05:08 2009

future spec

Posted Mon Jan 26 02:05:08 2009
Posted Mon Jan 26 02:05:08 2009
  • The generic node is expected to interface with the following peripherals

    • USB
    • Serial
    • SPI
    • I2C/TWI
    • CAN
    • 1-Wire
    • Analog inputs
    • GPIO
  • The state of the interface implementations are as follows:

    • USB
      • Not yet implemented.
    • Serial
      • Serial port communication is implemented.
      • Flow control not yet implemented.
    • SPI
      • General SPI communications implemented.
      • Device specific SPI functions implemented (SCP pressure sensor.)
    • I2C/TWI
      • Protocol algorithm documented.
      • Stub code for Master functions in code repository.
    • CAN
      • Not yet implemented.
    • 1-Wire
      • Not yet implemented.
    • Analog
      • All channels available
    • GPIO
      • All pins available
Posted Mon Jan 26 02:05:08 2009
  • LV2C:GFE:U2203 TPS63000 Hap Output Regulator
    • The HAP output regulator IC (TI TPS63000) takes the voltage supplied by the battery or charger in the HAP and DC-DC converts it to the required voltages for the remainder of the circuit. In most cases this is 3.3V, though with small modifications this voltage can be set to anywhere from 2.5 to 5.5 Volts. C2221 is a simple bulk input capacitor and serves to filter transients spkes and noise from the input power. R2011 and C2222 act in concert to create a time constant that is used to ensure that power is ready to be supplied befre the control circuit begins operation. L2202 is the Inductor used in the output filter of the Buck-Boost supply. R2216 and R2217 create a voltage divider that completes the feedback loop, R2216 is bypassed with capacitor C2223 to provide faster response to transient spikes. R2216 should be set for 1Mohm for operation of the circuit at 3.3Vdc or can be replaced by a 1.8Mohm resistor for the circuit to operate at 5Vdc, though Inductor L1 may need to be resized for this capability to be safely implimented. C2224 is used as the output filter capacitor and fulfills the role of reducing switch noise on the output. The circuit is synchronized to the 1.5MHz clock that is stepped down from the system clock by connection to the PS/Sync pin resulting in constant frequency operation that should not interfere in audio bands. The TPS63000 is noteworthy in that it acts as either a Buck regulator, or a boost regulator and not as an inefficient buck-boost regulator. It manages this by only activating two of it's four internal switches at a given time. The TPS63000 changes automatically from buck to boost operation as required on a per cycle basis.
  • LV2C:GFE:U2204 LTC4085 HAP Battery Charger and Power Path Controller
    • The HAP battery charger is built around the LTC4085 battery charger IC from Linear Technologies. The LTC4085 is a linear charger that has the capability to control 2 external P-MOS devices while charging the battery. During normal operation power is supplied by the SPS (LV2C:GFE:U2202) and there is no need for the battery. While power is supplied from the SPS The !ACPR! signal from the charger (AC power Present, though in our case the power is DC) will enable power-flow through Q2204 to the HAP Output Regulator (LV2C:GFE:U2003) bypassing the LTC4085. During loss of SPS power, the !ACPR! signal goes away blocking the reverse flow of power from the battery toward the SPS. Anytime the load draws the output voltage down, the ideal diode controller in the LTC4085 will begin to feed power from the battery to the load. This is done both through an internal ideal diode between the BAT and OUT pins, as well as by controlling the gate of Q2205 and using it in parallel with the internal diode. Paralleling the internal diode allows lower resistance sourcing of the battery power to the load. The !CHRG! pin is ground3ed to indicate the battery is charging when the charge current threshhold is passed. Threshhold is at 5000V/Rprog, or 50mA.
  • LV2C:GFE:D2202
    • Suggested Part: digikey 475-1278-1-ND (OSRAM Semiconductor: LS R976-NR-1-0-20-R18), 0805 package, 2.0Vfwd, 20mA test = 104mcd
    • When the battery charge current is above 50mA this LED is lit indicating the battery is charging. The LED is chosen as a red LED since it will be indicating that battery is charging when it is lit. We don't want it to draw a lot of power, so it has been chosen as a 2mA part in an 0805 package. While not bright, it should be useable. The current is set by resistor R2213 to be 2mA when the battery is charging (Vout-Vfwd)/Iset = (4.2V-20V)/2mA = 1100 ohms.
  • LV2C:GFE:B2201
    • Suggested Part:
  • LV2C:GFE:R2207 Rprog
    • Suggested Part: digikey (), 100k ohm, 0805 package.
    • The value of this resistor sets the charging current to the battery. The voltage across it can also be monitored by the LPC2348 to get an idea of the actual charge rate at any given moment. With Rprog = 100k ohms the charge current is set to 500mA. Ichrg(A)=50,000V/Rprog.
  • LV2C:GFE:R2208 Rclprog
    • Suggested Part: digikey (), 660 ohm, 0805 package.
    • The Current Limit Program resistor sets the input to output current limit. During normal operation and battery backup operation we will not be depending on the input to output current, as it is likely a hiugher voltage drop path than that of Q2204. It is currently set at 1.5A in case Q2204 is not populated on a given board, though that would also require pin 7 (wall) to be grounded. Icl(A)=1000V/Rclprog, Rclprog = 660 ohms for 1.515A max. Voltage on the Clprog pin is always proportional to the current flowing from In to Out and can be calculated by In(A)=(Vclprog/Rclprog)*1000
  • LV2C:GFE:R2209 Rnom
    • Suggested Part: digikey (), 121k, 1%, 0805 package.
    • This resistor forms a voltage divider circuit with the thermistor R2214 and its delta modifying resistor R2215 which results in a voltage dilivered to the NTC pin that represents the current temperature of the battery. As we want the thermistor to use a minimum amount of power in this design, we are using a 100k thermistor. The resistor value is then calculated by: Rnom=((Rcold-Rhot)/(2.815-.4086))*Rntc (where Rntc is 100k @25C and Rcold is 3.363 @0C, Rhot is .3507 @50C (3.363 and .3507 are from the conversion table for the vishay thermistor R2214 <>) resulting in a value of 125k, using the nearest standard 1% resistor results in Rnom = 121k ohms.
  • LV2C:GFE:R2211
    • Suggested part: 100 Ohms
    • Value from Datasheet. In combination with C2222 this resistor creates a time constant that forces the controller to wait for power to be applied to the switches before the controller begins operation.
  • LV2C:GFE:R2212 Gate Pull-Up
    • Suggested Part: digikey (), 1k ohm, 0805package.
    • This resistor is used to pull the gate voltage up to the output voltage when the !ACPR! signal is not present.
  • LV2C:GFE:R2213 Diode Current limit
    • Suggested Part: digikey (), 1000 Ohms, 0805 package.
    • This resistor sets the current through diode D2202. Current flows when the LTC4085 pulls the !CHRG! pin low indicating that the battery is charging. (Vout-Vfwd)/Iset = (4.2V-2.0V)/2mA = 1100 ohms, use 1k as it is still close and should result in only a 2.2mA current draw during use.
  • LV2C:GFE:R2214 Thermistor
    • Suggested Part: digikey 541-1140-1-ND (Vishay/Dale NTHS0805N17N1003JE)
    • This thermistor is an 0805 package with a 100k ohm value at 25C. Rntc is 100k @25C and Rcold is 3.363 @0C, Rhot is 0.3507 @50C (3.363 and .3507 are from the conversion table for the vishay thermistor R2214 <>)
  • LV2C:GFE:R2215 R-delta
    • Suggested Part: digikey (), 15k, 1%, 0805 package.
    • This resistor forms a voltage divider circuit with the thermistor R2214 and bias resistor R2209 which results in a voltage dilivered to the NTC pin that represents the current temperature of the battery. This particular resistor is in series with the thermistor and widens the temperature delta of the thermistor to set 50C as the the T-hot trip point. The resistor value is calculated by: Rdelta=([(.04086/(2.815-.4086))(Rcold-Rhot)]-Rhot)Rntc (where Rntc is 100k @25C and Rcold is 3.363 @0C, Rhot is .3507 @50C (3.363 and .3507 are from the conversion table for the vishay thermistor R2214 <>) resulting in a value of 16k, using the nearest standard 1% resistor results in Rnom = 15k ohms.
  • LV2C:GFE:R2216 Feedback Resistor
    • Suggested part: 1M ohm resistor for 3.3V operation.
    • R2216 calculation (3.3V): 1.12MOhm = R2((Vout/Vfb)-1), Vout = 3.3V, Vfb = 500mV, R2217 = 200kohms
    • Suggested part: 1.8M ohms for 5V operation, ensure that L2202 is capable of safe operation at 5Vdc before making this change.
    • R2216 calculation (5V): 1.8MOhm = R2((Vout/Vfb)-1), Vout = 5.0V, Vfb = 500mV, R2217 = 200kohms
  • LV2C:GFE:R2217 Feedback Resistor
    • suggested part: 200k Ohms
    • datasheet recommends keeping this part in the range of 200k ohms. No good reason to change this, though the efficiency could be slightly better if a larger value is used. Keep Feedback divider current at or above 1uA.
  • LV2C:GFE:C2219 Charge Timer Capacitor
    • Suggested Part: digikey (),
    • This capacitor sets the duration of the Charge timer for the LTC4085. Ttimer(hours)=(CtimerRprog3hours)/(0.1uF*100k)
  • LV2C:GFE:C2220 Bulk Output capacitor
    • Suggested Part: digikey (), 4.7uF
    • Datasheet recommends at least 4.7uF bypass cap from the OUT pin of the LTC4085 to ground. This capacitor holds up the output voltage when the battery is initially switched in, a job that could possibly be handled by C2221 if it is close enogh to the switches.
  • LV2C:GFE:C2221 Bulk Input Capacitor
    • Suggested part: 4.7uF, X7R ceramic
    • Value is as suggested in Datasheet, recommend small ceramic cap as close to pins as possible.
  • LV2C:GFE:C2222
    • Suggested part: 0.1uF, X7R ceramic
    • Value from datasheet. In combination with R2211 this capacitor creates a time constant that forces the controller to wait for power to be applied to the switches before the controller begins operation.
  • LV2C:GFE:C2223 FeedForward Capacitor.
    • Suggested part (3.3V): 2pF, X7R ceramic
    • C2223(3.3V)= 1.96pF = Feedforward capacitor = 2.2uS/R1
    • Suggested part (5.0V): 1.2pF, X7R ceramic
    • C2223(5V)= 1.22pF = Feedforward capacitor = 2.2uS/R1
  • LV2C:GFE:C2224 Bulk Output Capacitor
    • Suggested part: 22uF, X7R ceramic
    • C2224(min) = 11uF = Cout=5L(uF/uH), L=2.2uH. In combination with L2202, this capacitor acts as the output filter, datasheet recommends small ceramic cap as close to Vout and Pgnd pins as possible.
  • LV2C:GFE:L2202 Filter Inductor
    • Suggested Part: Digikey 587-1669-1-ND (Taiyo Yuden NR4018T2R2M), 2.2uH surface mount power inductor.
    • Recommended value: 2.2uH, 1.75A Irms, 2.26A Isat
    • L2202(suggested) = 2.2uH, this is the inductor value suggested in the datasheet for 3.3V operation.
    • L2202(min) = 1.57uH, this is the larger of 1.57uH = (Vout(Vinmax-Vout)/(Vinmaxf0.3A) or 1.34uH = (Vin_min(Vout-Vinmin))/(Vinminf0.3A), where Vout=3.3V, Vinmin=2.5V, Vinmax=4.2V, f=1.5MHz.
    • Imax(3.3V) = 1.74A, Isat= 2.26A = Imax+30%

  • Legacy devices : This category includes much of the front-end protection circuitry (Capstone 2006 Frontend Passive Block) and includes devices that have carried over from the 2006 capstone design, often with few or no changes.

  • LV2C:GFE:D2203 [Capstone2006 designation: D201] SPS Output Power On LED

    • Part Description: 1.9 V, 90 mcd @ 20 mA, 609 nm, 0805, Orange Diffused LED, CML Innovative Technologies Inc, CMDA5BA7D1S (Digi-Key p/n L71515CT-ND $3.00/10)
    • Purpose: This is an orange LED which is lit given that the nominal SPS 3.3 V rail is up. It is mainly used as an initial indicator of the 3.3 V rail's status. Orange was an arbitrary choice, however any other LEDs in the Glue Logic section needed to be different colors. The intensity and viewing angle are not critical since the only time the information from the LED is useful is in trouble shooting on the ground. It remains lit throughout the whole flight.
    • Specifications/ Calculations: From the CMDA5BA7D1S datasheet, Vf = 1.9 V. We specified the LED drive current to be 2 mA. See R2241 for I-V calculations.
    • Changes from LV2B to LV2C: Part number only.
  • LV2C:GFE:CR2201 [Capstone2006 designation: CR251] SPS Secondary Buck (Catch) Schottky Diode
    • Part Description: 30 V, 1.5 A, 4 ns, New MiniPower 2P, Cut Tape, RoHS Compliant???, Panasonic - SSG, MA2Q70500L (Digi-Key p/n MA2Q70500LCT-ND $0.83/1)
    • Purpose: CR2201 along with C2252 and L2202 form the second buck switching voltage power regulator which will be eventually regulated down to 5 V possibly with a low-dropout (LDO) linear voltage regulator. For consistency we used the same Schottky diode as CR200. Also the general understanding was that this secondary buck will power specific parts like 5 V ADCs on certain nodes (like the IMU) and we expect that this diode's rated specs are more than enough.
    • Specifications/ Calculations: Using the formula on page 9 in the LT1767 datasheet we calculated the average DC current that CR251 should be able to handle. Id,avg = Io (Vin - Vout) / Vin, where Io is the secondary output current of the SPS, Vin is the voltage at the node which is between L200a and L200b and Vout is the SPS secondary output voltage. We assumed that Vin would be switching somewhere between 1.6 V and 7 V. With Vout = 5 V and using the worst case Io = 1 A and Vin = 7 V values Id,avg = 286 mA (again this diode is overrated). We knew that not every node would need a secondary 5 V supply but even the ones that did, the added current should not cause overcurrent events (see U2250). Hopefully.
    • Changes from LV2B to LV2C: Part number only. Due to the nature of the new TPS63000, this is unlikely to function. In LV2B this was connected to a simple buck supply and could have worked. In LV2C, it is unlikely to raise the voltage from 3.3 to 5 volts, but it has been left in as it can be depopulated if it turns out to be nonfunctional.
  • LV2C:GFE:R2241 [Capstone2006 designation: R214 or R241] 3.3V Output Power On LED Current Limiter Resistor
    • Part Description: 649 ohm, 0805, 1%, 1/8 W, Cut Tape, RoHS Compliant, Rohm, MCR10EZHF6490 (Digi-Key p/n RHM649CCT-ND $0.38/10)
    • Purpose: R2241 is the SPS Output Power On LED current limiting resistor.
    • Specifications/ Calculations: From the datasheet Vf = 1.9 V, resulting in a current limiting resistor of about, R2241 = (3.3 V - 1.9 V) / (2 mA) = 650 ohms. The closest standard value was 649 ohms.
    • Changes from LV2B to LV2C: Part number only.
  • LV2C:GFE:C2252 [Capstone2006 designation: C252]
    • Part Description: TBD
    • Purpose: This cap along with C2252A, CR2251 and L2202 form the second buck switching voltage power supply which will be eventually regulated down to 5 V possibly with a low-dropout (LDO) linear voltage regulator. These are application specific caps whose values are mostly independent from the SPS design.
    • Specifications/ Calculations: The only difference between C2252 and C2252a are the packages and that only one of them will actually be on the PCB. Since we do not know any details about the actual application specific circuitry each SPS will power from an SPS design point of view, we chose to use both a 0805 and 1206 package. We chose two packages because we moved all relevant parts to the 0805 package from 1206 as in the LV2 SPS design and in case a specific application node needs a more beefy cap a 1206 package cap can be used. The lay out of the parts will not be side by side as suggested in the schematic but are offset and superimposed on top of each other on the same side of the PCB. Because only one cap will be used we offset the pads such that they are not directly on top of each other and either package can be placed down thus saving space. The values are TBD.
    • Changes from LV2B to LV2C: Part number only. Due to the nature of the new TPS63000, this is unlikely to function. In LV2B this was connected to a simple buck supply and could have worked. In LV2C, it is unlikely to raise the voltage from 3.3 to 5 volts, but it has been left in as it can be depopulated if it turns out to be nonfunctional.
  • LV2C:GFE:C2252A [Capstone2006 designation: C252A]
    • Part Description: TBD
    • Purpose: This cap along with C2252, CR2251 and L2202 form the second buck switching voltage power supply which will be eventually regulated down to 5 V possibly with a low-dropout (LDO) linear voltage regulator. These are application specific caps whose values are mostly independent from the SPS design.
    • Specifications/ Calculations: The only difference between C2252 and C2252a are the packages and that only one of them will actually be on the PCB. Since we do not know any details about the actual application specific circuitry each SPS will power from an SPS design point of view, we chose to use both a 0805 and 1206 package. We chose two packages because we moved all relevant parts to the 0805 package from 1206 as in the LV2 SPS design and in case a specific application node needs a more beefy cap a 1206 package cap can be used. The lay out of the parts will not be side by side as suggested in the schematic but are offset and superimposed on top of each other on the same side of the PCB. Because only one cap will be used we offset the pads such that they are not directly on top of each other and either package can be placed down thus saving space. The values are TBD.
    • Changes from LV2B to LV2C: Part number only. Due to the nature of the new TPS63000, this is unlikely to function. In LV2B this was connected to a simple buck supply and could have worked. In LV2C, it is unlikely to raise the voltage from 3.3 to 5 volts, but it has been left in as it can be depopulated if it turns out to be nonfunctional.

The following Eagle schematics represent the initial attempt at schematic capture for the HAP, it is broken into two parts, the charger with battery, and the output regulator.

HAP-Charger rev1.sch


HAP-Output-Regulator rev1.sch

Two primary contenders for the Li-Ion to 3.3V supply are the LTC3441 from Linear Technologies and the TPS63001 from TI. Both datasheets are linked below.

Linear LTC3441 Datasheet:,C1,C1003,C1042,C1116,C1790,P2149,D1054

TI TPS6300X Datasheet:

Update, the desire for on-chip control via an external thermistor in the battery has been expressed, this removes all existing parts from consideration including the Semtech SC806 IC that was previously chosen. This is a late game catch that results in significant redesign of the charger circuit, but should have little impact overall if the new IC is chosen quickly. To this end there are several ICs from Intersil that look promising. They are :ISL6292, ISL6292D, and the ISL9205. O these the ISL9205 looks most interesting initially.

INTERSIL ISL9205 Datasheet:

INTERSIL ISL6292 Datasheet:

INTERSIL ISL6292D Datasheet:

The SC806 had been chosen for the HAP battery charger and the LTC3441 had been chosen as the HAP output converter.

The datasheet for the Semtech SC806 lithium ion battery charger is here:,C1,C100,C149,P2432&id=623

Component choices for the SC806 Charger are as follows:

  • Cin
    • 0.1uF
    • Value is from the datasheet and is meant to eliminate voltage spikes due to sudden load changes or other issues.
    • This bulk capacitor needs to be placed as close to the input as possible.
  • Cout
    • 0.1uF
    • Value is from the datasheet and is meant to eliminate voltage spikes due to sudden load changes or other issues.
    • This bulk capacitor needs to be placed as close to the input as possible.
  • Rterm
    • 5k ohms
    • Rterm = (1.5V/Ipchrg) * 100, Ipchrg is the desired precharge current allowable values range from 10mA to 125mA and 30mA has been chosen. This value should include the expected current drain on the battery due to the load, as well as the actual precharge current. This will allow the battery to precharge while still supplying current to the load.
  • Rprgm
    • 1.5k ohms
    • Rprgm = (1.5V/Ifchrg) *1000, where Ifchrg is the fast charge current, which maxes out at 1.0A for this IC. This is the maximum charge rate into the battery, but must be set to include teh expected load current. If the load draws current beyond 1A, the additional current will have to be drawn from a combination of the battery and the SC806.

Battery choices:

model: PL-053048 manufacturer: Capacity: 750 mA Dimensions: 1.89 x 1.18 x .197 Datasheet:

model: 30124 manufacturer: Tenergy capacity: 450 mA dimensions: 1.65 x .83 x .24 datasheet:

model: GMB403040 manufacturer: GUANGZHOU MARKYN BATTERY CO., LTD Capacity: 450 mA Dimensions: 1.6 x 1.2 x .16 datasheet:

Posted Mon Jan 26 02:05:08 2009
  • LV2C:GFE:U2202 LT3972 Buck Regulator
    • The LT3972 is the heart of the SPS regulator. The LT3972 is a switching regulator from Linear Technologies. It can withstand input voltages as high as 62V which minimizes front end protection circuitry. It is synchronized to the 1.5MHz clock coming from the Micro-controller system.
    • The main function it performs is dropping the 10-20VDC coming in from the APS down to a more workable 5 volts. Specifically in our case it is set for 5.0V. For nodes without the HAP, the SPS can be reconfigured to run at 3.3VDC directly removing the need for the HAP and it's associated 3.3V output regulator.
  • LV2C:GFE:D2201 Catch Diode
    • Suggested Diode = Digikey Part number = PDS340DICT-ND, Diodes-Inc PDS340-13, has the following salient details: -- Vreverse = 40Volts , Iave = 3.0Amps , 6.6mm x 3.6mm footprint.
    • Alternate Diode = Digikey Part number = MBRA340T3GOSCT-ND , On-Semi MBRA340T3, has the following salient details: -- Vreverse = 40Volts , Iave = 3.0Amps , 6mm x 3mm footprint. Note apparent junction temperature difference and minimum buy compared to PDS340.
    • Id(avg) = (1.875,,2.14)A
    • Id(avg) = Iout(Vin-Vout)/Vin, Iout=2.5A(max), Vin = (10,,35)V (35V max for IC before shutdown due to OVP), Vout=5V
    • Use a Schottky diode, faster is better for efficiency, 40Vmax is fine since the OVP will shutdown the IC from 35V to 62V, beyond that the diode is likely to be the least of the worries, as the LT3972 will have perished.
  • LV2C:GFE:D???? Reverse Flow Diode (removed expect Q2250 to handle this job, no need for the extra loss it would introduce.)
    • This diode is in place to prevent a shorted input from drawing current in the reverse direction through the SPS and draining the battery. Utilizing the same part as the catch diode.
    • Use a Schottky diode, faster is better for fault protection, 40Vmax is overkill as the battery has a maximum voltage below 5Vdc, but is good for protection against a reversed input as well. Ideally this diode should create as little voltage drop as possible in the forward direction to minimize impact to operating efficiency.
  • LV2C:GFE:R2202 Frequency Set Resistor Rt
    • 26.7k Ohms
    • When Sync to 1.5MHz is desired, use the table value for 1.5MHz - 20%, or 1.2MHz.
    • For simulation use 20.2k ohms as this results in an operating frequency of 1.49MHz.
    • This resistor is not used or present in the final design (therefore no part number) the pin is connected to a clock for sync.
  • LV2C:GFE:R2204 Soft Start Resistor
    • 500k ohms
    • Works in combination with the Soft Start Capacitor below.
  • LV2C:GFE:R2205 Feedback resistor R1
    • suggested Resistor: Digikey Part Number = RHM536KCCT-ND, Rohm = MCR10EZHF5363, 536kOhm, 1%, 0805, thick film.
    • 532.911k ohms, use 532k ohms.
    • R1=R2((Vout/0.79V)-1 , where R2=100kohms, Vout=5Volts (chosen as Vin for the Charger of the HAP)
    • Could use 560k, but then R2 has to be 105k ohms.
  • LV2C:GFE:R2206 Feedback resistor
    • 100k ohms
    • This component value was chosen from the reference design.
    • It needs to be big enough to draw very little current through the feedback loop and still feed the appropriate voltages to the feedback error amp and the power good error amp.
  • LV2C:GFE:C2201 Input Capacitor Cin1 (OK to place slightly further from the IC)
    • Per Tim, using a physically large 10uF is fine, but then add a physically small 1uF cap in very close.
    • Suggested Capacitor = Digikey Part Number = 587-2247-1-ND , Taiyo Yuden = UMK325BJ106KM-T , 10uF , 50Volt, 20% , Ceramic , 1210 , X5R
  • LV2C:GFE:C2202 Input Capacitor Cin2 (Place as close to the IC as possible)
    • Suggested Capacitor : Digikey Part Number = 490-3909-1-ND , Murata = GRM31CR72A105KA01L , 1uF , 100Volt, 10% , Ceramic , 1206 , X7R
    • 15uF (could be in range of (10,,20)uF)
    • Xc = -j.01 ohms = 1/jwc , w = 2pi * 1.5MHz, c=10uF
    • So long as Xc is small at the switching frequency this cap will work, any cap in the range is fine, but the smaller they are the closer they need to be to the IC and the catch diode in order to effectively handle the EMI from the switching.
    • Watch out for Ringing during hot plugging, the cap needs to be able to withstand the full 62V that the LT3972 can during faults and plug in ringing.
    • Use types X5R and X7R, DO NOT USE type Y5V!! (warning per data-sheet)
  • LV2C:GFE:C2203 Frequency Compensation Capacitor
    • Suggested Capacitor = Digikey Part Number = PCC681BNCT-ND , Panasonic-ECG = ECU-V1H681KBN , 680pF , 50V , package = 0805.
    • Chosen as 15k ohms and 680pF from the reference schematic and the data-sheet.
    • Need help figuring these out.
  • LV2C:GFE:C2204 Boost and Bias Capacitor
    • Suggested Capacitor = Digikey Part Number = PCC1832CT-ND , Panasonic-ECG = ECJ-2YB1E224K , 0.22uF, 25V , package = 0805.
    • 0.22uF
    • This is set at 0.22uF per figure 5A in the data sheet. So long as the input voltage remains above 7.5V the boost/bias considerations appear minimal as there should be plenty of voltage available to successfully start the IC.
  • LV2C:GFE:C2205 Output Capacitor
    • Suggested Capacitor = Digikey Part Number = 587-2086-1-ND , Taiyo Yuden = TMK325BJ226MM-T , 22uF , 25Volt, 20% , Ceramic , 1210 package , X5R (Use of this part allows for a shorted switch and is the same part as the suggested input capacitor which is available through Digikey in lots of 10)
    • Alternate Capacitor = Digikey Part Number = 445-3945-1-ND , TDK = C3225X7R1C226K , 22uF , 16Volt, 10% , Ceramic , 3.2mm x 2.5mm , X7R
    • Alternate Capacitor = Digikey Part Number = 478-4594-1-ND , AVX = 1210YC226MAT2A , 22uF , 16Volt, 20% , Ceramic , 3.2mm x 2.5mm , X7R
    • 13.3uF minimum
    • Cout = 100/(Vout*f(sw)), Vout=5V, f(sw)=1.5MHz
    • Ensure that ESR is as low as possible to maximize efficiency (0.05 ohms or less)
    • Look for High performance electrolytic or Tantalum caps
    • Try to use type X5R or X7R
  • LV2C:GFE:C2225 Soft Start Capacitor
    • Suggested Capacitor = Digikey Part Number = PCC1840CT-ND , Panasonic-ECG = ECJ-2YB1H104K , 0.1uF, 50V , package = 0805.
    • Choose a large RC time constant to minimize voltage overshoot and reduce Imax for the switch at startup. Choose resistor to supply 20uA when RUN/SS is at 2.5V.
    • Want (3.75k, 585k, 875k) ohms for Vin = (10,14.2,20). 500k worked fine in LT-Spice and is the value chosen. As for the cap, it shows .22uF on the reference design, but won't run the system with that value in LT-spice, choosing 0.1uF as in the test fixture for the LT3972 works fine in the simulation and is the chosen cap value.
  • LV2C:GFE:L2201 Inductor
    • Suggested Inductor = Digikey Part number = 513-156-1-ND, Coiltronics DR74-6R8-R, has the following salient details: -- 6.8uH, Irms = 2.60Amps , Isat = 3.67Amps , DCR = 0.0418Ohms , Shielded , 8mm x 8mm x 4.25mm , Surface Mount.
    • 5.9uH min
    • Per data-sheet, start with di/dt for L and use dI= 1A = 0.4(Ioutmax) , Ioutmax=2.5A
    • Ipeak must be lower than Ilim (the switch current limit)
    • I(L-peak)= 3A = Ioutmax + dI/2 , Ioutmax = 2.5A, dI = 1A
    • This is good as Ilim ranges from (5.5A to 4.5A) and is always greater than 3A.
    • check ==> Ioutmax = Ilim-dI/2 = 4A , Ilim(worst case) = 4.5A, dI = 1A, So Ioutmax is at worst 4A, resulting in a value that is still above 3A, this is good.
    • Largest dI occurs at max Vin, choose L using the following formula:
    • L=[(Vout+Vd)/(FswdI)][1-((Vout+Vd)/Vinmax)], Vout=5V, Vd=0.4V, Fsw=1.5MHz, dI=1A, VinMax = 20V (possibly 30V during failures?)
    • L=5.2uH for Vin = 20V, or L=5.9uH for Vin = 30V
    • Larger values are OK as they will only make dI smaller resulting in improved system responses.
    • RMS rating of L must be greater than Imax = 2.5A
    • Saturation current should be about 30% higher, Isat = 3.25A, but want Isat above 5A during startup, shorts, Over Voltages, and other failures.
    • To keep efficiency high, DCR should be kept below 0.1 ohm.
    • To minimize EMI, use a shielded toroid with a ferrite core.
    • Again, larger L is good since they should have better DCR values, smaller ripple current (dI), and an easier time keeping out of discontinuous mode, but the physical size will be a limiting factor.

  • Legacy devices : This category includes much of the front-end protection circuitry (Capstone 2006 Frontend Passive Block) and includes devices that have carried over from the 2006 capstone design, often with few or no changes.
  • LV2C:GFE:U2250 [Capstone2006 designation: U250]
    • Part Description: MAX5902AAETT +72 V, SOT-23, Simple Swapper How-Swap Controller. Ordered samples from vendor, no Digi-Key.
    • Purpose: This hot-swap controller IC serves two purposes: (1) circuit-breaker and (2) the first stage of UVLO protection. The version we chose had a input voltage range of +9 V to +72 V, a 300 mV circuit-breaker threshold voltage, limited inrush current ("soft start") and was an automatic retry circuit-breaker. It also had a built-in thermal shutdown and active low power good (!PGOOD) indicator output pin. The device needed a UVLO resistor divider network (R2250, R2251) and an external PMOSFET (Q2250) switch. There are four events which will cause Q250 to turn off: (1) if there is undervoltage at the input, (2) if there is overcurrent, (3) if the die temperature exceeds +125 C and (4) the ON/!OFF pin 6 is forced low for at least 10 ms. See the MAX5902 datasheet.
    • Specifications/ Calculations: The reasons we chose the 300 mV automatic retry circuit breaker version was that we wanted the SPS to be able to recover from a fault condition by itself and we expect that the nominal load current will not be very close to the 400 mA maximum limit but closer to 300 mA or less. Hence steady-state currents in the range of 400 mA to 500 mA qualify as an overcurrent event and should be detected. To avoid wasting power dissipated by Q220's RDS(on) and R2252, those values should be kept low, therefore the voltage across them should also be low and the 300 mV threshold version satisfied that. Upon power up U2250 keeps Q2250 off and if trigger events (1) and (2) are non-existent, then it gradually turns Q2250 on to saturation in approximately 150 ms. The drain of Q2250 is gradually enhanced at a rate of about 9 V/ ms. This start sequence limits the inrush current giving some "soft-start" protection to its load. Once all transients are gone before the 150ms time period and Q2250 is fully saturated, U2250's circuit-breaker functionality comes up and monitors the Vds of Q2250 between pins 1 and 2. Before this initial power up 150 ms period there is no circuit-breaker functionality. If any one of the 4 trigger events occurs U2250 will turn Q2250 off, de-assert !PGOOD (output a logic high) and reinitiate the start sequence given that the trigger event(s) disappears during the 150 ms period, if not the 150 ms period will repeat. There are two typical turn off times regarding Q2250: 10 ms and 4 us. If there is an ON/!OFF or UVLO trigger event, they need to exist for 10 ms before U2250 turns Q2250 off, which will take an unspecified amount of time. If there is an overcurrent or temperature trigger event, then Q2250 is turned off in 4 us. If the trigger events disappear after Q2250 turns off within 150 ms, then the normal start sequence is reinitiated. Since the purpose of U2250 was to be a circuit-breaker we decided not to use the ON/!OFF pin to turn Q2250 off via any SPS feedback. Only an UVLO condition would be a trigger event. The UVLO threshold was specified as 9 V. See R2250 and R2251. This meant that when a trigger event other than a UVLO condition happens, U2520 would turn Q2250 off in 4 us and would reinitiate the start sequence after a trigger event free 150 ms time period. We needed a way for the LPC2368 (U2201) microcontroller to turn off the SPS, so we connected a logic level NMOSFET (Q2282) to a GPIO pin and connected the drain of Q2282 to the ON/!OFF pin of U2250. Also we connected the active low !PGOOD pin to another GPIO pin for monitoring and/or interrupt purposes. See the GLUE Logic section regarding U2280 and Q2282. See R2253 and Q2251 for the "overvoltage to overcurrent" trigger event emulation. One bad thing that we did not like was the relatively high supply current of U2250 being 1 mA to 2 mA. We believe that U2250 will draw the most current from the power bus when the SPS is in a standby/shutdown mode. NOTE: According to the MAX5902 datasheet there are multiple package options for the different versions of the MAX5902: a TDFN and SOT23 package. All SOT23 packages have the specification that, "This device is constructed using a unique set of packaging techniques that impose a limit on the thermal profile the device can be exposed to during board level solder attach and rework. This limit permits only the use of solder profiles recommended in the industry standard specification, JEDEC 020A, paragraph 7.6, Table 3 for IR/VPR and convection reflow. Preheating is required. Hand or wave soldering is not allowed.", which may or may not present a problem.
    • changes from LV2B to LV2C: Part number only. Part must still be ordered outside of digikey (vendor still shows samples in stock)
  • LV2C:GFE:U2251 [Capstone2006 designation: U251]
    • Undervoltage/Overvoltage Protection (U2251)
    • Part Description: Nanopower Push-Pull Output Comparator with Voltage Reference, 1.8 V < Vin < 5.5 V, SOT-23-6, Tape & Reel (TR), RoHS Compliant, Texas Instruments, TLV3012AIDBVT (Digi-Key p/n 296-16830-2-ND $262.50/2250) NOTE: Ordered samples from vendor no Digi-Key.
    • Purpose: This comparator compares the specified divided SPS output voltage (see R2254, R2255) to its internal reference voltage (1.242 V) for an overvoltage trigger event at the SPS output. It is powered by a secondary supply consisting of CR2250 and C2250. Also it has a pseudo low-pass filter consisting of C2251 and its output (pin 1) with the input being pin IN+ (pin 3). See CR2250, C2250 and C2251 respectively.
    • Specifications/ Calculations: We wanted a low power push-pull output comparator to get rail to rail output swing (approximately 200 mV to 3.1 V) and have reasonable switching and rise/fall times, on the order of several microseconds and nanoseconds respectively. We tied the IN- pin (pin 4) to the internal reference voltage REF pin (pin 5) which will be compared to the divided SPS output voltage at its IN+ pin (pin 3). See R254, R255 and C2251. The "undervoltage" protection is actually provided by CR2250 and C2250 where U2251 will remain powered for a specified amount of time if the +3.3 V SPS output rail drops. See CR2250 and C2250.
    • changes from LV2B to LV2C: Part number only, order from vendor, not Digikey.
  • LV2C:GFE:CR2250 [Capstone2006 designation: CR250]
    • TLV3012AIDBVT "Secondary Power Supply" Schottky Diode (CR2250)
    • Part Description: 30 V, 1.5 A, 4 ns, New MiniPower 2P, Cut Tape, RoHS Compliant???, Panasonic - SSG, MA2Q70500L (Digi-Key p/n MA2Q70500LCT-ND $0.83/1)
    • Purpose: CR2250 and C2250 form U2251's power supply. This diode prevents C2250 from discharging anywhere but to the V+ supply pin of U2251. U2251 is indirectly powered by the +3.3 V SPS rail. Pin 6 (V+) of U2251 will be charged to a value very close to the +3.3 V SPS rail. As U2251 draws more current when needed and its V+ voltage drops CR2250's Vf below the SPS voltage CR2250 will re-charge C2250. Therefore the average DC current through CR2250 is not easily calculable but will be on the order of tens to hundreds of uA. Schottky diodes were chosen for their fast switching and reverse recovery times. In response to a overvoltage event at the +3.3 V SPS output, U2251 will output a logic high and turn Q2251 on which will cause an overcurrent event at U2250 which will in response turn Q2250 off thus circuit breaking the bus rail from the SPS and the +3.3 V SPS output voltage rail will go to zero. That is the sequence of events without delay times. This is the way U2251 emulates an overcurrent event from an overvoltage event.
    • Specifications/ Calculations: CR2250 has a low forward voltage and U2251 has an input voltage supply range of 1.8 V to 5.0 V so when the SPS voltage is being brought up C2250 is being charged through CR2250 leaving the voltage of SPS minus the Vf of CR2250 at pin 6 (V+) of U2251: V+ = 3.3 V - 0.05 V = 3.25 V (approximately). See the first graph on page 2 of the MA2Q705 datasheet given that the steady state nominal forward current through CR2250 < 1 mA. See C2250.
    • changes from LV2B to LV2C: Part number only, this is another digikey non-stock part. It will have to be respecified or ordered from another vendor.
  • LV2C:GFE:Q2250 [Capstone2006 designation: Q250]
    • Part Description: -60 V, -3 A, SOT-23-6, P-Channel MOSFET, Cut Tape, RoHS Compliant, Zetex Inc, ZXMP6A17E6TA (Digi-Key p/n ZXMP6A17E6CT-ND $0.75/1)
    • Purpose: This is the external PMOSFET of U2250 which will turn off given that there is one or more of the four trigger events as described earlier. See U2250. U2250 uses the RDS(on) of the saturated Q2250 as a current sense resistor which generates a Vds voltage which is detected across the Vs (Pin 1) and DRAIN (Pin 2) pins and if it is greater than some threshold voltage, U2250 will switch Q2250 off thus breaking the circuit.
    • Specifications/ Calculations: The maximum SPS output current specified was 400 mA. There are three circuit-breaker threshold voltage versions of U2250: 300 mV, 400 mV and 500 mV. For certain reasons the 300 mV threshold part was chosen. See U2250. Therefore the RDS(on) of the PMOS should be around 300 mV / 400 mA = 0.75 ohm. We used a value of 1 ohm. See R2252. Even though the PMOS is used as a switch (cutoff and saturation) and not an amplifier (cutoff, triode and saturation) we wanted to remove dependence of U2250's threshold voltage detection from the less precise RDS(on) of Q2250 and to a more precise sense resistor. Therefore we added a current sense resistor (R2252) in series with the drain of Q2250 to produce a circuit-breaker resistor, Rcb, which is the series combination of Q2250's RDS(on) and R2252 between the two pins 1 and 2 of U2250. We chose a PMOS with a low RDS(on) compared to the needed calculated value needed to trip the circuit-breaker thereby making R2252 close to Rcb in value. Therefore Q2250 is used mostly as a switch and the voltage drop across R2252 is used to trigger the switch. See R2252. The breakdown voltage of Q2250 has to be greater than 20 V and should have a low "turn on" capacitance. We do not care so much about the Vt but it does affect the "turn on" capacitance but these factors were not considered.
    • changes from LV2B to LV2C: Part number only. Price has gone down slightly at digikey to $0.75
  • LV2C:GFE:Q2251 [Capstone2006 designation: Q251]
    • Part Description: 100 V, 170 mA, RDS(on) = 10 ohm @ Vgs = 4.5V, SOT-23, Cut Tape, RoHS Compliant???, N-Channel Logic-Level MOSFET, Infineon Technologies, BSS123E6327 (Digi-Key p/n BSS123INCT-ND $0.36/1)
    • Purpose: This is a logic-level NMOSFET. When an overvoltage at the +3.3 V SPS output occurs, U251 will output a logic high turning Q251 on and thus conducting current through R253. The current flowing through R253 also flows through Rcb and its magnitude is dependent on the value of R253 and the bus voltage at the time (nominal value of 16.8 V). When there is no overvoltage at the +3.3 V SPS output U251 outputs a logic low thus keeping Q251 off.
    • Specifications/ Calculations: Since the gate of this FET would be driven by the output of a comparator in U251 it would be best for the FET to be a logic-level device. Other concerns was for the drain-source breakdown voltage to be higher than 30 V as the highest possible DC value the bus voltage rail would be is 20 V.
    • changes from LV2B to LV2C: Part number only. Original Part is non-stock, call to order at digikey. Should be re-sourced re-specified, or ordered as a vendor sample.
  • LV2C:GFE:Q2282 [Capstone2006 designation: Q282]
    • Part Description: Logic level N-channel mosfet, 100V, SOT23, Fairchild p/n: BSS123 (Digikey p/n: BSS123NCT-ND $0.29/1)
    • Purpose: This Nmosfet allows a Microcontroller GPIO pin to activate the shutoff of U2250 (circuit-breaker) resulting in a disconnection of the APS supply to the SPS.
    • Specifications/calculations: See the GLUE logic section of Capstone2006 for detailed explanation of this part.
    • changes from LV2B to LV2C: Part number only. Still available through Digikey.
  • LV2C:GFE:TVS2201 [Capstone2006 designation: TVS200]
    • Part Description: 18 V, SMB, Unidirectional, Cut Tape, RoHS Non-Compliant, Diodes Inc, SMBJ18A-13 (Digi-Key p/n SMBJ18ADICT-ND $0.89/1)
    • Purpose: A transient voltage suppressor (TVS), this "zener like" diode protects the SPS (specifically U2202) in the event of an overvoltage at the input.
    • Specifications/ Calculations: It should have a breakdown voltage of about 20 V (unlikely maximum bus voltage) and a current carrying capacity greater than the fuse rated current. It should have a fast response time and be unidirectional. In the event of a sustained overvoltage at the input the only allowable part which can be destroyed is the fuse, F200. That is what we want.
    • changes from LV2B to LV2C: Part number. The original capstone2006 part is no longer available in digikey. Respecify or find new vendor. One suggested replacement is B72500D200A60V7 (Digikey p/n: 495-3413-1-ND $0.20/1) This is a simple Zener type ESD suppressor in an 0603 package.
    • Another replacement possibility is: V2F118C400Y1FDP, digikey p/n:478-2486-1-ND. The difficulty here is that new replacement doesn't handle the current that we are looking for, it maxes out at 1A and would blow before the fuse.
    • A final possibility, as the LT3907 is capable of withstanding up to 62V, it could be argued to simply not populate this part, though some ESD protection would be nice.
  • LV2C:GFE:F2201 [Capstone2006 designation: F201] Node Power Supply Fuse
    • Part Description: 2000 mA, 63 V, 1206, Fast Acting Short Time Lag, RoHS Compliant, TYCO Electronics, 1206SFF200F/63-2 (Digi-Key p/n 1206SFF200F/63CT-ND $0.46/1)
    • Purpose: This fuse protects the SPS from currents greater than 2000 mA. Its direct purpose however is to protect the power bus from a short circuit fault on the SPS side.
    • Specifications/ Calculations: Since the specified maximum SPS current is 2000 mA we chose a fuse rated at 2000 mA. The opening time for the fuse according to its datasheet is .05 s at a current of 8 A, or 5 s at 5 A. Currents of 2 A or below are 4 hours minimum, therefore this fuse will only protect the SPS or power bus from gross currents due to some fault on either side (power bus or SPS) and not to keep the SPS output current within spec, that is U250's job.
    • changes from LV2B to LV2C: Part number. New value reflecting the higher current rating of the updated SPS.
  • LV2C:GFE:R2218 [Capstone2006 designation: R215] Chassis Ground to Node Ground isolation resistor
    • Part Description: 100 kohm, 0805, 1%, 1/8 W, Cut Tape, RoHS Compliant, Rohm, MCR10EZHF1003 (Digi-Key p/n RHM100KCCT-ND $0.38/10)
    • Purpose: R2218 provides a DC path from the SPS ground to chassis ground. See page 29 of the CAN Node Switch Mode Power Supply (SPS) (200) section in the Component Design for LV2 Power Electronics (Except Main Battery) engineering design notes.
    • Specifications/ Calculations: 100 kohm worked.
    • changes from LV2B to LV2C: Part number only. No recognized need for other changes.
  • LV2C:GFE:R2250 [Capstone2006 designation: R250]
    • Part Description: 61.9 kohm, 0805, 1%, 1/8 W, Cut Tape, RoHS Compliant???, Rohm, MCR10EZHF6192 (Digi-Key p/n RHM61.9KCCT-ND $0.38/10)
    • Purpose: R2250 is part of the UVLO resistor divider of U2250.
    • Specifications/ Calculations: The UVLO voltage was specified to be 9 V. See page 8 and Figure 3 in the MAX5902 datasheet. Letting R251 = 10.0 kohm and using the typical value of Von/!off = 1.26 V, the UVLO formula from page 8 in the datasheet is R250 = R251 * ((VUVLO / (Von/!off)) - 1) = 61.4 kohm. The closet standard value was 61.9 kohm.
    • changes from LV2B to LV2C: Part number only.
  • LV2C:GFE:R2251 [Capstone2006 designation: R251]
    • Part Description: 10.0 kohm, 0805, 1%, 1/8 W, Cut Tape, RoHS Compliant???, Rohm, MCR10EZHF1002 (Digi-Key p/n RHM10.0KCCT-ND $0.38/10)
    • Purpose: R2251 is part of the UVLO resistor divider of U2250.
    • Specifications/ Calculations: R251 was specified to be 10.0 kohm. See page 8 and Figure 3 in the MAX5902 datasheet.
    • changes from LV2B to LV2C: Part number only.
  • LV2C:GFE:R2252 [Capstone2006 designation: R252]
    • Part Description: 0.82 ohm, 0805, 1%, 1/8 W, Cut Tape, RoHS Compliant???, Panasonic - ECG, ERJ-6RQFR82V (Digi-Key p/n P.82DCT-ND $2.10/10)
    • Purpose: This resistor dominates the circuit-breaker resistor's (Rcb) value. It is in series with the drain (hence RDS(on) of Q2250 to make up Rcb. The voltage drop across it is used to detect an overcurrent event given that it is greater than 300 mV. See Q2250 and U2250. Note: This value may change due to board level testing results.
    • Specifications/ Calculations: Since the typical value of RDS(on) of Q2250 is 0.125 ohm and Rcb was about equal to 1 ohm, R2252 = Rcb - RDS(on) = 0.875 ohm. The closet standard value was 0.82 ohm. Given this value of Rcb and the circuit-breaker trip threshold voltage of 300 mV, the maximum SPS current which can be drawn before an overcurrent event is Imax = 300 mV / (0.125 ohm + 0.82 ohm) = 317 mA which is under the specified maximum SPS current spec.
    • changes from LV2B to LV2C: Part number only. Probably need to recalculate the default value, but it is likely to be changed during board level testing regardless.
  • LV2C:GFE:R2253 [Capstone2006 designation: R253]
    • Part Description: 47.0 kohm, 0805, 1%, 1/8 W, Cut Tape, RoHS Compliant???, Rohm, MCR10EZHF4702 (Digi-Key p/n RHM47.0KCCT-ND $0.38/10)
    • Purpose: R253 along with Q2251 will "emulate" an overcurrent trigger event as seen by U2250 when an overvoltage at the SPS output trigger event as seen by U2251 occurs. See Q2251. When the SPS +3.3 V output rises above a certain threshold, the output of U2251 goes high, turning Q2251 on. When this happens it pulls pin 2 of U2250 very close to ground and current flows through R253 and Q251. Now that pin 2 is close to ground and pin 1 is normally close to the power bus voltage this is much greater than 300 mV this causing an overcurrent trigger event for U2250. R2253 limits the extra current pulled through Q2251 when it is turned on.
    • Specifications/ Calculations: In normal SPS operation, the voltage drop across Rcb will be less than 300 mV and R2253 is connected to the high impedance pin 2 of U2250 so no current flows through it. If there is an overvoltage trigger event at the SPS output, Q2251 is turned on conducting current through R2253 which will have a voltage drop of approximately 300 mV less than the power bus voltage: VR2253 = 16.8 V - 300 mV = 16.5 V. This results in a current boost of about IR2253 = 16.5 V / 47 kohm = 351 uA which is negligible.
    • changes from LV2B to LV2C: Part number only.
  • LV2C:GFE:R2254 [Capstone2006 designation: R254]
    • TLV3012AIDBVT UVLO Lockout Resistor Network (R254, R255)
    • Part Description: 18.2 kohm, 0805, 1%, 1/8 W, Cut Tape, RoHS Compliant???, Rohm, MCR10EZHF1822 (Digi-Key p/n RHM18.2KCCT-ND $0.38/10)
    • Purpose: R254 along with R255 form a voltage divider with respect to the +3.3 V SPS output rail. When there is an overvoltage at the +3.3 V SPS output the voltage at the IN- pin (pin 4) of U2251 will be greater than the internal reference voltage of U2251 (typically 1.242 V) and will result in the comparator in U2251 outputing a logic high value. When the SPS output is below a certain threshold the input voltage (pin 4) to U2251 is less than the internal reference voltage and the comparator's output is a logic low.
    • Specifications/ Calculations: From the LPC2148 datasheet the maximum supply voltage it can handle is 3.6 V therefore we specified that if the +3.3 V SPS output was to reach 3.5 V we would want this to qualify as an overvoltage trigger event. Since we have been using several 10.0 kohm resistors we specified R255 to be 10.0 kohm. Therefore using the overvoltage trigger event value to be 3.5 V and the compared voltage to be 1.242 V we solved for R254: 1.242 V = (3.5 V * R255)/ (R255 + R254) and solving for R254 = 18.18 kohm. The closet standard value was 18.2 kohm.
    • changes from LV2B to LV2C: Part number only, though this is a non-stock digikey part, it should be easy to locate alternate sources, need new value for 5.0V sps rail.
  • LV2C:GFE:R2255 [Capstone2006 designation: R255]
    • Part Description: 10.0 kohm, 0805, 1%, 1/8 W, Cut Tape, RoHS Compliant???, Rohm, MCR10EZHF1002 (Digi-Key p/n RHM10.0KCCT-ND $0.38/10)
    • Purpose: R255 along with R254 form a voltage divider with respect to the +3.3 V SPS output rail. When there is an overvoltage at the +3.3 V SPS output the voltage at the IN- pin (pin 4) of U2251 will be greater than the internal reference voltage of U2251 (typically 1.242 V) and will result in the comparator in U2251 outputing a logic high value. When the SPS output is below a certain threshold the input voltage (pin 4) to U2251 is less than the internal reference voltage and the comparator's output is a logic low.
    • Specifications/ Calculations: We specified R255 = 10.0 kohm. See R254.
    • changes from LV2B to LV2C: Part number only, need to recalc value for new sps rail at 5.0V
  • LV2C:GFE:C2206 [Capstone2006 designation: C203] Node Power Supply Filter Capacitor
    • Part Description: 22 uF, 25 V, Tant, T491 Series, 7343-31 (EIA), Cut Tape, RoHS Compliant???, Kemet, T491D226K025AT (Digi-Key p/n 399-3782-1-ND $0.65/1)$file/F3102T491.pdf.
    • Purpose: C203 acts as a noise filter between the power bus and SPS. It also serves as a local energy storage node.
    • Specifications/ Calculations: It needs to have a voltage rating greater than 20 V and a low equivalent series resistance (ESR) thus a tantalum capacitor was chosen due to their low ESR at a higher capacitance.
    • changes from LV2B to LV2C: Part number only. No recognized need for other changes, though the voltage rating is a bit low.
  • LV2C:GFE:C2207 [Capstone2006 designation: C204]
    • Part Description: 0.33 uF, 50 V, 0805, X7R, Cut Tape, RoHS Compliant, Murata Electronics North America , GRM219R71H334KA88D (Digi-Key p/n 490-3327-1-ND $3.09/10)
    • Purpose: C2207 is a high frequency noise filter between the power bus and SPS. It did not have to have as high a capacitance as C2206 so the trade off was to get a lower value at a low ESR.
    • Specifications/ Calculations: It needs to have a voltage rating greater than 20 V and the capacitance value was not very critical but should be much lower than C2206.
    • changes from LV2B to LV2C: Part number only. No recognized need for other changes, though the voltage rating is a bit low.
  • LV2C:GFE:C2250 [Capstone2006 designation: C250]
    • TLV3012AIDBVT "Secondary Power Supply" Cap (C2250)
    • Part Description: 2.7 uF, 10 V, 0805, X5R, Cut Tape, RoHS Compliant, Kemet, C0805C275K8PACTU (Digi-Key p/n 399-3127-1-ND $7.02/10)$file/F3102X5R.pdf.
    • Purpose: Along with CR2250, C2250 forms the power supply for U2251. C2250 is charged to a voltage less a forward diode drop (see CR2250) from the +3.3 V SPS output rail under normal operating conditions. U2251 draws a constant 2.8 uA supply current so CR2250 is always trickle charging C2250, therefore the voltage across C2250 will be VfCR2250 = 0.37 V (this is worst case Vf) less than 3.3 V. See CR2250. However U2251 can operate from 1.8 V to 5.0 V. Since the voltage at V+ of U2251 is approximately 3.0 V and the lower limit of the supply voltage range of U2251 is 1.8 V, C2250 has to be able to store enough charge such that if the SPS output drops down by a certain amount of voltage, U2251 is still powered for a certain amount of time thus preventing U2251 from power cycling if the SPS output ramps back up to +3.3 V. We want to prevent this because as U2251 is powering up the comparator could possibly switch. That behavior has to be observed in experiment but we assume that the initial state of the comparator will be logic low. If the SPS output toggles or drops in value we want U2251 to have power for a specified amount of time in case the magnitude of the voltage change of a transient causes a trigger event but lasts a very short amount of time or would normally shut down U2251, thus avoiding the time needed for U2251 to power cycle. When the overvoltage at the SPS output event occurs there is a finite amount of time required before Q2250 is eventually turned off namely the propagation delay of the comparator in U2251, the turn-on delay time of Q2251, the time to turn off Q2250 by U2250 and the turn-off delay time of Q2250. These typical times as are 12 us, 8 ns, 4 us and 26.2 ns as specified on pages 3, 3, 8 and 4 in the TLV3012, BSS1223, MAX5902 and ZXMP6A17E6 datasheets respectively, resulting in an ideal propagation delay of about 17 us. After these propagation delay times, Q2250 is off and the input voltage Vin (pin 2) of U200 is zero volts (after C201 is discharged) triggering the SHDN\ pin and turning off U200. When this happens the power supply to U2251 is essentially removed, so the time constant for C2250 has to be long enough such that as U2250 is going through its start sequence (150 ms) the comparator in U2251 can output a logic low and turn Q2251 off as the voltage it is comparing, IN+ (pin 3), to its internal reference voltage, REF, is the divided (see R254, R255) SPS output rail voltage which at this time is zero volts. To make sure that this sequence of events happen we specified U2251 to have power long enough to turn Q2251 back off while U2250 is turning back on again. Under normal operating conditions (no UVLO event) and assuming that there are no long or catastrophic transients, U2251 should always be on. This design will always keep U2250 on which will minimize any unknown states at the comparator output resulting from U2251 turning off, then on again, etc. Upon initial power up we assume that the output of U2251 will be logic low keeping Q2251 off to prevent a false overcurrent event for U2250 which may prevent the SPS from working as U2250 will never turn Q2250 on and will just cycle. This seems unlikely because upon initial power up, U2251 has no power and cannot output logic high. However as the +3.3 V SPS output is being brought up the output of the comparator is undefined which is not good being directly connected to the gate of Q2251 but we still think that Q2251 will remain off or will rapidly switch off if it is ever on after the transients.
    • Specifications/ Calculations: We calculated the needed amount of charge, Qt, C2250 would have to store such that U2251 would have power for at least 0.5 s (our specified amount of time U2251 should have power during these events) given that the SPS output voltage dropped by 1 V from which we calculated C2250's capacitance. C2250 = [((Qt * 1.2) + (Iq * tp))] / Vp, where Qt = [((Input Capacitance) * Vt) + ((Reverse Transfer Capacitance) * Vin)], Iq = 2.8 uA, ts = 0.5 s, Vp = 1 V Qt is the sum of products of the input capacitance of Q2251 times the maximum threshold voltage plus the reverse transfer capacitance of Q2251 times the maximum Vds swing, namely Vin. Iq is the supply current of U2251, tp is the amount of time we want U2251 to have power, Vp is the amount of voltage the SPS output drops and the 1.2 term is a fudge factor because Qt is dependent on some other factors not explicitly shown. tp was specified to be 0.5 s, this time is the time C2250 can supply power to U2251 which is longer than the propagation delays mentioned above including some margin just in case any trigger events do not go away and U2250 has to go through another 150 ms start sequence. If the trigger events remain longer than the 0.5 s, then U2251 turns off and the whole SPS will go through another initial power up sequence. Vp = 1 V, i.e. the input voltage V+ (pin 6) to U2251 can drop to about 3.0 V - 1 V = 2 V. Iq = 2.8 uA, see page 3 in the TLV3012 datasheet. Qt = (85 pF * 2 V) + (15 pF * 20V) = 470 pC, see page 3 in the BSS123 datasheet. C2250 = 1.40056 uF we decided to chose a 2.7 uF cap to give us a little more tp due to any unknown delays and the like we did not consider.
    • changes from LV2B to LV2C: Part number only, still in stock at Digikey.
  • LV2C:GFE:C2251 [Capstone2006 designation: C251]
    • TLV3012AIDBVT Overvoltage Detection Cap (C2251)
    • Part Description: 0.015 uF, 100 V, 0805, X7R, Cut Tape, RoHS Compliant, AVX Corporation, 08051C153KAT2A (Digi-Key p/n 478-1359-1-ND $2.64/10)
    • Purpose: C2251 is used as a low-pass filter to node IN+ (pin 3) of U2251 and as positive feedback to make the comparator switch faster and to make sure that once the comparator is switching it completes the transistion. Under normal SPS operation, when U2251 is keeping Q2251 off, the OUTPUT (pin 1) of U2251 is at zero volts thus the cap is acting like a low-pass filter, the node connected to pin 3 of U2251 is the input to the filter. If there are transients at the +3.3 V SPS output this node will also experience proportional transients. If the magnitude of these transients are great enough (but fast in duration) then U2251's comparator switches, which is undesirable so we want true ovevoltage events to trigger the comparator. C2251 will remove most of these false event transients. When there is a true overvoltage event the comparator starts to switch. If there is another transient (false event) where the magnitude of the voltage goes below the threshold the comparator could possibly try to switch back. We want the comparator to avoid reacting to false transients. C2251 prevents this because as the comparator is rising its output voltage, C2251 raises the voltage on pin 3 of U2251 thus reinforcing the comparator to keep on raising its output voltage. This is positive feedback. Also C2251 decreases the rise time of the comparator. Basically if there is something weird going on at the SPS output, i.e. it is oscillating between 0 V and 3.3 V, C2251 will help to make sure that U2251 turns Q2251 off, eventually turning off Q2250 which will give a 150 ms time period for the weird things to go away, given that U2251 does not shutdown during these transients. See C2250.
    • Specifications/ Calculations: We wanted C2251 to filter transients which lasted less than 100 us therefore we need to find the output resistance C2251 sees under a transient (or AC) condition. We used the zero-time coefficient technique to solve for the resistance and eventual capacitance. Under a transient condition the SPS output and comparator output are grounded (DC voltage) and removing C2251 the resistance it sees is the parallel combination of R254 and R255. R254 || R255 = 6.46 kohm, with an RC = 100 us we can solve for C = 15.4 nF. The closest standard value is 0.015 uF. The voltage rating needs to be greater than 20 V just for safe measure.
    • changes from LV2B to LV2C: Part number only, still in stock at Digikey.
  • LV2C:GFE:L2203 [Capstone2006 designation: L201] Power Bus input Choke
    • Part Description: CMS2-4-R Common Mode Inductors 102 uH, Micro-PAC Plus Package, RoHS Compliant, Cut Tape, (Digikey p/n: 513-1115-1-ND, $3.37/1).
    • Purpose: Common mode choke (balanced inductor). It is used as an EMI filter between the power bus and the SPS.
    • Specifications/ Calculations: The capstone 2006 value was chosen through a trial and error process from the previous LV2 SPS design. Each inductor of the choke is 100 uH. See page 13 of the CAN Node Switch Mode Power Supply (SPS) (200) section in the Component Design for LV2 Power Electronics (Except Main Battery) engineering design notes
    • changes from LV2B to LV2C: Capstone 2006 part (CMS1-11-R) has gone non-stock at digikey and replacements are available in lots of 2000. New suggested part(CMS1-7-R) is dissimilar in value, but same physical size.

The following SPS parameters have also been calculated:

  • Maximum Switch frequency and duty cycle calculations
    • F(switch max) = (Vd + Vout) / (t(on min)(Vd + Vin - Vsw)), Vd=0.5V,Vout=3.3V,t(on min)=150nS,Vin=(10,14.2,20)V,Vsw=0.5@max load
    • F(sw max)= 3.66MHz for Vin=10V, 2.58MHz for Vin=14.2V, 1.83MHz for Vin=20V
    • Min Duty Cycle = 22.5% = F(sw)*t(on min)
    • Max Duty Cycle = 77.5% = 1 - (F(sw) * t(on min))
    • These all appear fine as they are all well above the 1.5MHz we are planning to sync at.
  • Input Voltage range (at 1.5MHz operation)
    • Vin(max) = 36.66V = [(Vout+Vd) / (f(sw) * t(on min))] - Vd + Vsw, Vd=0.5V (catch diode drop), Vout=3.3V, t(on min)=100nS, Vsw=0.5V
    • Vin(min) = 6.47V= [(Vout+Vd) / [1 - (f(sw) * t(off min))]] - Vd + Vsw

The LT3972 from Linear Technologies has been chosen for the SPS. While the SC806 Battery Charger (Semtech) and the LT3441 Lithium-Ion to 3.3V regulator (Linear Technologies) have been chosen for the HAP.

An initial draft Eagle library file has been created to contain the IC information for the SPS and HAP. Eventually it will need to be integrated into the generic PSAS Eagle library. For now it is located here, followed by an initial draft of the Eagle .sch schematic file for the SPS-HAP. Note that the .libr file has a prefix of 0 to keep it at the top of the list during use in Eagle.

Looks like the LT3972 is the IC of choice at the moment. It is fully capable of everything we need it to do. Would be nice if it had a built in fuse and connector. The reference data-sheet contains the following diagram which describes the desired circuit. We will need to add an input diode to prevent the battery backup from draining through a shorted input. Desired operation at 1.5MHz or so will increase efficiency of the converter from the 2MHz reference circuit, though the inductor would be (slightly) smaller at the higher frequency.

Start by choosing the primary Switching regulator that will take to 10-20V input from the APS and deliver 5V to the HAP. The following is a short list of potential IC choices and some notes about each.

Part# Vin(V) Vout(V) IoutMax(A) Sync(MHz) Iq(uA) Enable OVP(V) UVLO Power_Good Package(mm) Notes
[LT3480] (3.6-36) (0.8-20) 2 (0.25-2) 160 Yes 38V ? Yes 3x3 DFN Soft Start
[LT3680] (3.6-36) (0.8-30) 3.5 (0.25-2) 160 Yes no no Yes 3x3 DFN Soft Start. Thermal Protection.
[LT3972] (3.6-33) (0.8-30) 3.5 (0.25-2) 160 Yes 38V ? Yes 3x3 DFN Soft Start. Thermal Protection.
[LTM8023] (3.6-36) (0.8-10) 2 (0.25-2) (0.1-120) Yes no no Yes 11.25X9 uModule Soft Start. Shorted In Protection.
[LTM8032] (3.6-36) (0.8-10) 2 (0.25-2) (0.6-120) Yes no no Yes 15X9 uModule Soft Start. Ultra-LowNoise
[LM20333] (4.5-36) (0.8-8) 3 (0.25-1.5) (2300-3000) Yes Yes Yes Yes 6x6 TSSOP Internal Current limiting and thermal shutdown.
[TPS54140] (3.5-42) (2.5->5) 1.5 (0.3-2.2) 116 Yes Yes Yes Yes 3x5 TSSOP Soft Start. Internal Current limiting and thermal shutdown.
[TPS54160] (3.5-60) (2.5->5) 1.5 (0.3-2.2) 116 Yes Yes Yes Yes 3x5 TSSOP Soft Start. Internal Current limiting and thermal shutdown.

Direct data download

Posted Mon Jan 26 02:05:08 2009

Microcontroller LPC2368FBD100

  • LV2C:GFE:U2201
  • For our application we are using:
    • GPIO pins to communicate with and control devices on the same node
    • CAN bus to communicate with other nodes and the Flight Computer
    • USB to communicate with devices on this and other nodes as well as the Flight Computer
    • I2C to communicate with devices on this node
    • A/D to read devices on this node
    • External 32.678 kHz crystal for RTC clock
    • External 12.0 MHz crystal for internal PLL and sync to switching power supplies in the SPS and HAP
    • Various Reset, test, control and debug lines.

Interface Description
    Information from the LPC2368 web site

Pin Descriptions
    From the Web site

Pin Connections
    What pin goes where, why? x100
    What GPIO pins are in use
    What GPIO pins are available?

GLUE Devices
    Part Description

The following is a listing of the LPC2368 pins used in the generic node. The far right column indicates whether a pin is available for use during design of non-generic nodes.

Sort by Signal || || Sort by Pin and Purpose (Generic Node Only)
Pin Signal || || Pin Signal Destination Available
46 PORT0.0/RD1/TXD3/SDA1 || || 1 TDO Debug-P7 no
47 PORT0.1/TD1/RXD3/SCL1 || || 2 TDI Debug-P6 no
98 PORT0.2/TXD0 || || 3 TMS Debug-P8 no
99 PORT0.3/RXD0 || || 4 !TRST Debug-P9 no
81 PORT0.4/I2SRX_CLK/RD2/CAP2.0 || || 5 TCK Debug-P5 no
80 PORT0.5/I2SRX_WS/TD2/CAP2.1 || || 6 PORT0.26/AD0.3/AOUT/RXD3 No-connect yes
79 PORT0.6/I2SRX_SDA/SSEL1/MAT2.0 || || 7 PORT0.25/AD0.2/I2SRX_SDA/TXD3 No-connect yes
78 PORT0.7/I2STX_CLK/SCK1/MAT2.1 || || 8 PORT0.24/AD0.1/I2SRX_WS/CAP3.1 No-connect yes
77 PORT0.8/I2STX_WS/MISO1/MAT2.2 || || 9 PORT0.23/AD0.0/I2SRX_CLK/CAP3.0 No-connect yes
76 PORT0.9/I2STX_SDA/MOSI1/MAT2.3 || || 10 VDDA A_3P3 no
48 PORT0.10/TXD2/SDA2/MAT3.0 || || 11 VSSA A_GND no
49 PORT0.11/RXD2/SCL2/MAT3.1 || || 12 VREF CPU_VREF no
62 PORT0.15/TXD1/SCK0/SCK || || 13 VDD(DCDC)(3V3) 3.3VHAPOUT no
63 PORT0.16/RXD1/SSEL0/SSEL || || 14 !RSTOUT Debug-P3 no
61 PORT0.17/CTS1/MISO0/MISO || || 15 VSS GND no
60 PORT0.18/DCD1/MOSI0/MOSI || || 16 RTCX1 RTC_XTAL-A no
59 PORT0.19/DSR1/MCICLK/SDA1 || || 17 !RESET Debug-P2 no
58 PORT0.20/DTR1/MCICMD/SCL1 || || 18 RTCX2 RTC_XTAL-B no
57 PORT0.21/RI1/MCIPWR/RD1 || || 19 VBAT CPU_VBAT no
9 PORT0.23/AD0.0/I2SRX_CLK/CAP3.0 || || 21 PORT1.30/VBUS/AD0.4 No-connect yes
8 PORT0.24/AD0.1/I2SRX_WS/CAP3.1 || || 22 XTAL1 CPU_XTAL1 no
7 PORT0.25/AD0.2/I2SRX_SDA/TXD3 || || 23 XTAL2 CPU_XTAL2 no
6 PORT0.26/AD0.3/AOUT/RXD3 || || 24 PORT0.28/SCL0 No-connect yes
25 PORT0.27/SDA0 || || 25 PORT0.27/SDA0 No-connect yes
24 PORT0.28/SCL0 || || 26 PORT3.26/MAT0.1/RXD3 No-connect yes
29 PORT0.29/USB_D+ || || 27 PORT3.25/MAT0.0/PWM1.2 No-connect yes
30 PORT0.30/USB_D- || || 28 VDD(3V3) 3.3VHAPOUT no
95 PORT1.0/ENET_TXD0 || || 29 PORT0.29/USB_D+ USB_D+ no
94 PORT1.1/ENET_TXD1 || || 30 PORT0.30/USB_D- USB_D- no
93 PORT1.4/ENETTXEN || || 31 VSS@1 GND no
92 PORT1.8/ENET_CRS || || 32 PORT1.18/USBUPLED/PWM1.1/CAP1.0 GPIOUSBHighSpeed no
91 PORT1.9/ENET_RXD0 || || 33 PORT1.19/CAP1.1 No-connect yes
90 PORT1.10/ENET_RXD1 || || 34 PORT1.20/PWM1.2/SCK0 No-connect yes
89 PORT1.14/ENETRXER || || 35 PORT1.21/PWM1.3/SSEL0 No-connect yes
88 PORT1.15/ENETREFCLK || || 36 PORT1.22/MAT1.0 No-connect yes
87 PORT1.16/ENET_MDC || || 37 PORT1.23/PWM1.4/MISO0 No-connect yes
86 PORT1.17/ENET_MDIO || || 38 PORT1.24/PWM1.5/MOSI0 No-connect yes
32 PORT1.18/USBUPLED/PWM1.1/CAP1.0 || || 39 PORT1.25/MAT1.1 No-connect yes
33 PORT1.19/CAP1.1 || || 40 PORT1.26/PWM1.6/CAP0.0 No-connect yes
34 PORT1.20/PWM1.2/SCK0 || || 41 VSS@2 GND no
35 PORT1.21/PWM1.3/SSEL0 || || 42 VDD(DCDC)(3V3)@1 3.3VHAPOUT no
36 PORT1.22/MAT1.0 || || 43 PORT1.27/CAP0.1 No-connect yes
37 PORT1.23/PWM1.4/MISO0 || || 44 PORT1.28/PCAP1.0/MAT0.0 No-connect yes
38 PORT1.24/PWM1.5/MOSI0 || || 45 PORT1.29/PCAP1.1/MAT0.1 No-connect yes
39 PORT1.25/MAT1.1 || || 46 PORT0.0/RD1/TXD3/SDA1 CAN no
40 PORT1.26/PWM1.6/CAP0.0 || || 47 PORT0.1/TD1/RXD3/SCL1 CAN no
43 PORT1.27/CAP0.1 || || 48 PORT0.10/TXD2/SDA2/MAT3.0 No-connect yes
44 PORT1.28/PCAP1.0/MAT0.0 || || 49 PORT0.11/RXD2/SCL2/MAT3.1 No-connect yes
45 PORT1.29/PCAP1.1/MAT0.1 || || 50 PORT2.13/!EINT3/MCIDAT3/I2STX_SDA No-connect yes
21 PORT1.30/VBUS/AD0.4 || || 51 PORT2.12/!EINT2/MCIDAT2/I2STX_WS No-connect yes
20 PORT1.31/SCK1/AD0.5 || || 52 PORT2.11/!EINT1/MCIDAT1/I2STX_CLK No-connect yes
75 PORT2.0/PWM1.1/TXD1/TRACECLK || || 53 PORT2.10/!EINT0 Debug-P10 no
74 PORT2.1/PWM1.2/RXD1/PIPESTAT0 || || 54 VDD(3V3)@1 3.3VHAPOUT no
53 PORT2.10/!EINT0 || || 55 VSS@3 GND no
52 PORT2.11/!EINT1/MCIDAT1/I2STX_CLK || || 56 PORT0.22/RTS1/MCIDAT0/TD1 No-connect yes
51 PORT2.12/!EINT2/MCIDAT2/I2STX_WS || || 57 PORT0.21/RI1/MCIPWR/RD1 No-connect yes
50 PORT2.13/!EINT3/MCIDAT3/I2STX_SDA || || 58 PORT0.20/DTR1/MCICMD/SCL1 No-connect yes
73 PORT2.2/PWM1.3/CTS1/PIPESTAT1 || || 59 PORT0.19/DSR1/MCICLK/SDA1 No-connect yes
70 PORT2.3/PWM1.4/DCD1/PIPESTAT2 || || 60 PORT0.18/DCD1/MOSI0/MOSI No-connect yes
69 PORT2.4/PWM1.5/DSR1/TRACESYNC || || 61 PORT0.17/CTS1/MISO0/MISO No-connect yes
68 PORT2.5/PWM1.6/DTR1/TRACEPKT0 || || 62 PORT0.15/TXD1/SCK0/SCK No-connect yes
67 PORT2.6/PCAP1.0/RI1/TRACEPKT1 || || 63 PORT0.16/RXD1/SSEL0/SSEL No-connect yes
66 PORT2.7/RD2/RTS1/TRACEPKT2 || || 64 PORT2.9/USB_CONNECT/RXD2/EXTIN0 No-connect yes
65 PORT2.8/TD2/TXD2/TRACEPKT3 || || 65 PORT2.8/TD2/TXD2/TRACEPKT3 No-connect yes
64 PORT2.9/USB_CONNECT/RXD2/EXTIN0 || || 66 PORT2.7/RD2/RTS1/TRACEPKT2 No-connect yes
27 PORT3.25/MAT0.0/PWM1.2 || || 67 PORT2.6/PCAP1.0/RI1/TRACEPKT1 No-connect yes
26 PORT3.26/MAT0.1/RXD3 || || 68 PORT2.5/PWM1.6/DTR1/TRACEPKT0 No-connect yes
82 PORT4.28/MAT2.0/TXD3 || || 69 PORT2.4/PWM1.5/DSR1/TRACESYNC No-connect yes
85 PORT4.29/MAT2.1/RXD3 || || 70 PORT2.3/PWM1.4/DCD1/PIPESTAT2 No-connect yes
17 !RESET || || 71 VDD(3V3)@2 3.3VHAPOUT no
14 !RSTOUT || || 72 VSS@4 GND no
100 RTCK || || 73 PORT2.2/PWM1.3/CTS1/PIPESTAT1 No-connect yes
16 RTCX1 || || 74 PORT2.1/PWM1.2/RXD1/PIPESTAT0 No-connect yes
18 RTCX2 || || 75 PORT2.0/PWM1.1/TXD1/TRACECLK No-connect yes
5 TCK || || 76 PORT0.9/I2STX_SDA/MOSI1/MAT2.3 No-connect yes
2 TDI || || 77 PORT0.8/I2STX_WS/MISO1/MAT2.2 No-connect yes
1 TDO || || 78 PORT0.7/I2STX_CLK/SCK1/MAT2.1 No-connect yes
3 TMS || || 79 PORT0.6/I2SRX_SDA/SSEL1/MAT2.0 No-connect yes
4 !TRST || || 80 PORT0.5/I2SRX_WS/TD2/CAP2.1 No-connect yes
19 VBAT || || 81 PORT0.4/I2SRX_CLK/RD2/CAP2.0 CAN_Autobaud no
28 VDD(3V3) || || 82 PORT4.28/MAT2.0/TXD3 No-connect yes
54 VDD(3V3)@1 || || 83 VSS@6 GND no
71 VDD(3V3)@2 || || 84 VDD(DCDC)(3V3)@2 3.3VHAPOUT no
96 VDD(3V3)@3 || || 85 PORT4.29/MAT2.1/RXD3 No-connect yes
13 VDD(DCDC)(3V3) || || 86 PORT1.17/ENET_MDIO StatusLED2 no
42 VDD(DCDC)(3V3)@1 || || 87 PORT1.16/ENET_MDC StatusLED1 no
84 VDD(DCDC)(3V3)@2 || || 88 PORT1.15/ENETREFCLK No-connect yes
12 VREF || || 90 PORT1.10/ENET_RXD1 GPIOBAT!CHRG! no
97 VSS@5 || || 96 VDD(3V3)@3 3.3VHAPOUT no
83 VSS@6 || || 97 VSS@5 GND no
11 VSSA || || 98 PORT0.2/TXD0 Debug-P11 no
22 XTAL1 || || 99 PORT0.3/RXD0 Debug-P12 no
23 XTAL2 || || 100 RTCK Debug-P4 no

Direct data download


The following list contains a pin to signal reference for the LPC2368 Microcontroller.

Sort by Signal Sort by Pin
Pin Signal Pin Signal
46 PORT0.0/RD1/TXD3/SDA1 1 TDO
47 PORT0.1/TD1/RXD3/SCL1 2 TDI
98 PORT0.2/TXD0 3 TMS
99 PORT0.3/RXD0 4 !TRST
80 PORT0.5/I2SRX_WS/TD2/CAP2.1 6 PORT0.26/AD0.3/AOUT/RXD3
78 PORT0.7/I2STX_CLK/SCK1/MAT2.1 8 PORT0.24/AD0.1/I2SRX_WS/CAP3.1
77 PORT0.8/I2STX_WS/MISO1/MAT2.2 9 PORT0.23/AD0.0/I2SRX_CLK/CAP3.0
48 PORT0.10/TXD2/SDA2/MAT3.0 11 VSSA
49 PORT0.11/RXD2/SCL2/MAT3.1 12 VREF
62 PORT0.15/TXD1/SCK0/SCK 13 VDD(DCDC)(3V3)
56 PORT0.22/RTS1/MCIDAT0/TD1 20 PORT1.31/SCK1/AD0.5
9 PORT0.23/AD0.0/I2SRX_CLK/CAP3.0 21 PORT1.30/VBUS/AD0.4
8 PORT0.24/AD0.1/I2SRX_WS/CAP3.1 22 XTAL1
7 PORT0.25/AD0.2/I2SRX_SDA/TXD3 23 XTAL2
6 PORT0.26/AD0.3/AOUT/RXD3 24 PORT0.28/SCL0
25 PORT0.27/SDA0 25 PORT0.27/SDA0
24 PORT0.28/SCL0 26 PORT3.26/MAT0.1/RXD3
29 PORT0.29/USB_D+ 27 PORT3.25/MAT0.0/PWM1.2
30 PORT0.30/USB_D- 28 VDD(3V3)
95 PORT1.0/ENET_TXD0 29 PORT0.29/USB_D+
94 PORT1.1/ENET_TXD1 30 PORT0.30/USB_D-
91 PORT1.9/ENET_RXD0 33 PORT1.19/CAP1.1
90 PORT1.10/ENET_RXD1 34 PORT1.20/PWM1.2/SCK0
87 PORT1.16/ENET_MDC 37 PORT1.23/PWM1.4/MISO0
86 PORT1.17/ENET_MDIO 38 PORT1.24/PWM1.5/MOSI0
32 PORT1.18/USBUPLED/PWM1.1/CAP1.0 39 PORT1.25/MAT1.1
33 PORT1.19/CAP1.1 40 PORT1.26/PWM1.6/CAP0.0
34 PORT1.20/PWM1.2/SCK0 41 VSS@2
35 PORT1.21/PWM1.3/SSEL0 42 VDD(DCDC)(3V3)@1
36 PORT1.22/MAT1.0 43 PORT1.27/CAP0.1
37 PORT1.23/PWM1.4/MISO0 44 PORT1.28/PCAP1.0/MAT0.0
38 PORT1.24/PWM1.5/MOSI0 45 PORT1.29/PCAP1.1/MAT0.1
39 PORT1.25/MAT1.1 46 PORT0.0/RD1/TXD3/SDA1
40 PORT1.26/PWM1.6/CAP0.0 47 PORT0.1/TD1/RXD3/SCL1
43 PORT1.27/CAP0.1 48 PORT0.10/TXD2/SDA2/MAT3.0
44 PORT1.28/PCAP1.0/MAT0.0 49 PORT0.11/RXD2/SCL2/MAT3.1
74 PORT2.1/PWM1.2/RXD1/PIPESTAT0 54 VDD(3V3)@1
53 PORT2.10/!EINT0 55 VSS@3
27 PORT3.25/MAT0.0/PWM1.2 67 PORT2.6/PCAP1.0/RI1/TRACEPKT1
26 PORT3.26/MAT0.1/RXD3 68 PORT2.5/PWM1.6/DTR1/TRACEPKT0
85 PORT4.29/MAT2.1/RXD3 70 PORT2.3/PWM1.4/DCD1/PIPESTAT2
17 !RESET 71 VDD(3V3)@2
14 !RSTOUT 72 VSS@4
4 !TRST 80 PORT0.5/I2SRX_WS/TD2/CAP2.1
28 VDD(3V3) 82 PORT4.28/MAT2.0/TXD3
54 VDD(3V3)@1 83 VSS@6
71 VDD(3V3)@2 84 VDD(DCDC)(3V3)@2
96 VDD(3V3)@3 85 PORT4.29/MAT2.1/RXD3
42 VDD(DCDC)(3V3)@1 87 PORT1.16/ENET_MDC
31 VSS@1 92 PORT1.8/ENET_CRS
55 VSS@3 94 PORT1.1/ENET_TXD1
72 VSS@4 95 PORT1.0/ENET_TXD0
97 VSS@5 96 VDD(3V3)@3
83 VSS@6 97 VSS@5
11 VSSA 98 PORT0.2/TXD0
22 XTAL1 99 PORT0.3/RXD0
23 XTAL2 100 RTCK

Direct data download


Posted Mon Jan 26 02:05:08 2009
Posted Mon Jan 26 02:05:08 2009