- 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 <http://www.vishay.com/docs/33011/convtabs.pdf>) 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 <http://www.vishay.com/docs/33011/convtabs.pdf>)
- 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 <http://www.vishay.com/docs/33011/convtabs.pdf>) 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) http://www.chml.com/pdf/temp/CMDA5BA7D1S.pdf.
- 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) http://www.semicon.panasonic.co.jp/ds/eng/SKH00017BED.pdf.
- 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) http://www.rohm.com/products/databook/r/pdf/mcr10.pdf.
- 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.
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: http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1042,C1116,C1790,P2149,D1054
TI TPS6300X Datasheet: http://focus.ti.com/lit/ds/symlink/tps63000.pdf
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: http://www.intersil.com/data/fn/fn9252.pdf
INTERSIL ISL6292 Datasheet: http://www.intersil.com/data/fn/fn9105.pdf
INTERSIL ISL6292D Datasheet: http://www.intersil.com/data/fn/fn9166.pdf
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: http://www.semtech.com/pc/downloadDocument.do?navId=H0,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: Batteryspace.com Capacity: 750 mA Dimensions: 1.89 x 1.18 x .197 Datasheet: http://www.batteryspace.com/ProductImages/li-ion/053048.pdf
model: 30124 manufacturer: Tenergy capacity: 450 mA dimensions: 1.65 x .83 x .24 datasheet: http://www.all-battery.com/productimages/lipopacks/3.7V450mah602040.pdf
model: GMB403040 manufacturer: GUANGZHOU MARKYN BATTERY CO., LTD Capacity: 450 mA Dimensions: 1.6 x 1.2 x .16 datasheet: http://www.gmbattery.com/dl/cp11/li-ion/LIPO/BlueTooth/GMB403040.pdf