Power Supply Connections and Components
Figuring out front end current consumption
What's the power consumption of the flight computer carrier board? Roughly, it's the components of the TQM5200, the Innodisk flash HDD, running the secondary USB which can take up to 500 mA, and the various other misc circuits (debugging LEDs, clock dividers, USB transceivers, CAN transcevers, etc).
| Component | V | I | P | I @ Vbat = 10V @ 70% |
|---|---|---|---|---|
| TQM5200 | 3.3 V | 1.96 A | 6.47 W | 0.924 A |
| INNOdisk | 3.3 V | 0.14 A | 0.46 W | 0.066 A |
| USB-2 | 5.0 V | 0.50 A | 0.25 W | 0.179 A |
| Misc | 3.3 V | 0.25 A | 0.83 W | 0.118 A |
| TOTAL | 1.29 A |
So the power supply front end should be able to handle 1.3 A continuously.
IC Units
UXXXX: LTM4619 (Dual, 26VIN, 4A DC/DC μModule Regulator)
Description: This is SPS which creates 5V and 3.3V output from 10-20V input. This component was chosen because of high current output (4A) and simplicity of design. It has inductors in the module thus we do not need to design whole buck converter. SPS is synchronized with external clock of 500kHz from the 24MHz oscillator on TQM5200. 24MHz signal is divided down to 500kHz through U1009 and U1010. See those components notes. Its’ input current and output voltage is protected by Q1000. 500kHz of external was chosen because it is easier to be generated from 24MHz oscillator using frequency divider.
UXXXX: LTM4619 Pin Description
Pin Name Description Vin Protected power is supplied decoupled with 2 10uF capacitors. Vout1 Output 5V, 500mA decoupled with 100uF Vout2 Output 3.3V, 2.2A decoupled with 100uF PGND Power ground: Just connect to ground. INTVcc Internal 5V regurator we don't use this. EXTVcc This is only required when Vin<6V, so we float this pin. SGND Signal ground, just connected to ground. MODE/PLLIN We use this pin as PLLIN of 500kHz. (clock is supplied from clystal oscillator on TQM5200) FREQ/PLLFLTR Since we use external clock, we leave this pin unconnected. TK/SS1 0.2nF capacitor is connected to set soft-start time 123us. (tsoft-start=0.8V*Css/1.3uA) TK/SS2 0.2nF capacitor is connected to set soft-start time 123us.(tsoft-start=0.8V*Css/1.3uA) VFB1 R1000 (11.5kΩ) is used to program 5V output voltage on Vout1. Refer table1 of datasheet VFB2 R1001 (19.1kΩ) is used to program 3.3V output voltage on Vout2. Refer table1 of datasheet COMP1 Current Control Threshold Noconnection Followed typical application. COMP2 Current Control Threshold Noconnection Followed typical application. PGOOD Only connected to test point because we do not care. RUN1 Floated to enable Vout1 RUN2 Floated to enable Vout2 SW1 Test pin to check operation frequency SW2 Test pin to check operation frequency
U1001: MAX5902AAETT (+72V SOT23 Simple Swapper Hot-Swap Controller)
- Description:This hot-swap controller IC serves two purposes: (1) circuit-breaker and (2) UVLO protection. This controller turns off Q1000 under several conditions. (1) if there is under voltage at the input, (2) if there is overcurrent, (3) if the die temperature exceeds +125 C (4) if SPS-5V output exceeds 5.46V and (5) if SPS-3.3V output exceeds 3.6V.
*Note
(1) Under voltage protection threshold is set to be 9V by voltage divider R1103 and R1104.
(2) Over current threshold of 1.62A is set by series resistance of R1002 and RDS(on) of Q1000.
(4) Overvoltage protection of SPS-5V is sensed by U1003 and toggled by Q1001.
(5) Overvoltage protection of SPS-3.3V is sensed by U1002 and toggled by Q1002.
Justification:We use the same part from capstone 2009[LV2C:GFE:U2250]
However we reduced some functionalities.(1)PGOOD is not used in our circuit because we do not care PGOOD signal durling launch.(2)We do not have MOSFET connected to ON/OFF pin because we do not let microcontroller to toggle circuit breaker.U1001: MAX5902AAETT Pin Description
Pin Name Description ON/OFF Connected to UVLO resistor divider network R1103 and R1104. Their value were selected to set UVLO voltage to be 9V. See R1103 VS Monitors voltage dropp across Q1000 DRAIN Monitors voltage dropp across Q1000 GATE Used to shut off Q1000 PGOOD We do not use PGOOD GND Connected to ground
- Description:This hot-swap controller IC serves two purposes: (1) circuit-breaker and (2) UVLO protection. This controller turns off Q1000 under several conditions. (1) if there is under voltage at the input, (2) if there is overcurrent, (3) if the die temperature exceeds +125 C (4) if SPS-5V output exceeds 5.46V and (5) if SPS-3.3V output exceeds 3.6V.
U1002: TLV3012AIDBVT (Comparator with Voltage Reference)
- Description: U1002 watches overvoltage on SPS-3.3V output. In the event SPS-3.3V output exceeds 3.6V, it turns on Q1002 and makes pin2 (Drain) of U1001 close to GND, then U1001 shuts Q1000 off: SPS is disconnected from power bus. See capstone 2009 [LV2C:GFE:U2251].
Justification: We use the same part from capstone 2009[LV2C:GFE:U2250]
U1002: TLV3012AIDBVT Pin Description
Pin Name Description V+ Connected to C1010 which act like a power supply to avoid power cycling when SPS output decline to certain level. 2.7uF capacitor was chosen to store charge more than 0.5s. See C1010. REF integrated voltage reference IN- Use REF(1.242V) for voltage reference IN+ Connected to the voltage divider which programs overvoltage shut down threshold at 3.6V for SPS-3.3V. See R1005 and R1007. V- Ground OUT Used to switch Q1002 which shut off the breaker when overvoltage occurs
- Description: U1002 watches overvoltage on SPS-3.3V output. In the event SPS-3.3V output exceeds 3.6V, it turns on Q1002 and makes pin2 (Drain) of U1001 close to GND, then U1001 shuts Q1000 off: SPS is disconnected from power bus. See capstone 2009 [LV2C:GFE:U2251].
U1003: TLV3012AIDBVT (Comparator with Voltage Reference)
- Description: U1003 watches overvoltage on SPS-5V output. In the event SPS-5V output exceeds 5.46V, it turns on Q1001 and makes pin2 (Drain) of U1001 close to GND, then U1001 shuts Q1000 off: SPS is disconnected from power bus. See capstone 2009 [LV2C:GFE:U2251].
Justification: We use the same part from capstone 2009[LV2C:GFE:U2250]
U1003: TLV3012AIDBVT Pin Description
Pin Name Description V+ Connected to C1012 which act like a secondary power supply to avoid power cycling when SPS output drops down by certain level. 2.7uF capacitor was chosen to store charge more than 0.5s. See C1012. REF integrated voltage reference IN- Use REF(1.242V) for voltage reference IN+ Connected to the voltage divider which programs overvoltage shut down threshold at 5.46V for SPS-5V. See R1006 and R1008. V- Ground OUT Used to switch Q1001 which shut off the breaker when overvoltage occurs
- Description: U1003 watches overvoltage on SPS-5V output. In the event SPS-5V output exceeds 5.46V, it turns on Q1001 and makes pin2 (Drain) of U1001 close to GND, then U1001 shuts Q1000 off: SPS is disconnected from power bus. See capstone 2009 [LV2C:GFE:U2251].
U1009: SN74LVC2G80DCU (Dual positive-edge-triggered D-type Flop-flop)
Description: This D-type flip-flops divide 24MHz clock signal from TQM5200 by 4, and it is cascaded to U1010 (SN74LS92D: divide by 12 counter) to finally create 500kHz clock. Since we did not know output voltage levels of 24MHz oscillator on TQM5200, and to ensure this clock drives flip-flops, we had to use the same supply voltage (3.3V) for this component. Output voltage level (Running at 3.3V supply) of this component also had to meet input voltage levels of U1010 (SN74LS92D: divide by 12 counter).
U1009: SN74LVC2G80DCU Pin Description
Pin Name Description 1CLK Connected to 24MHz oscillator (input of the first divide by 2 flip-flop) 1D '#1Q is fedback to this pin to function as a divide by 2 flip-flop '#1Q Feedback for 1D, this pin is also connected to input of the second divide by 2 flip-flop) 2CLK input of the second divide by 2 flip-flop 2D '#2Q is fedback to this pin to function as a divide by 2 flip-flop '#2Q Feedback for 2D, this pin is also cascaded to U1010 (divide by 12 counter)
U1010: SN74LS92D (Divide-by-12)
Description: This component is divide-by-12 counter cascaded from divide-by-4 flip-flops. In order to generate 500kHz clock from 24MHz clock it has to be divided 48. However there were no such a single chip divider thus we cascaded divide-by-4 and 12. It has 2V of logic high minimum input voltage it is within output voltage level of divide-by-4 flip-flops, and it has high-level output voltage 2.4V (minimum) which is high enough to drive UXXXX (LTM4619). This divider outputs clock signal with duty ratio of 50%. Pull-down resistor on the pin QD pulls to logic low while starting up the board and it enable UXXXX (LTM4619) force continuous operation until UXXXX receive 500kHz clock signal.
U1010: SN74LS92D Pin Description
Pin Name Description CKB This pin is connected to QA in order to function as a divide by 12 counter. CKA This is an input of divide by 12 counter. It is cascaded form divide by 4 flip-flops QA Feedback to CKB according to the datasheet QB Test Point (Not used) QC Test Point (Not used) QD Output of the divide by 12 counter (500kHz clock) with 100k ohms pull-down resister R0(1) Connected to GND to enable divide by 12 counter R0(2) Connected to GND to enable divide by 12 counter
resistors
R1000: 11.5 kohm 0805, 1%, 1/8 W
- Description: 11.5 kohm feedback resistor which programs output voltage of Vout1 of UXXXX (LTM4619) to be 5V. See the equation and the table 1 of the datasheet of LTM4619.
R1001: 19.1k ohms 0805, 1%, 1/8 W
- Description: 19.1k ohms feedback resistor which programs output voltage of Vout2 of UXXXX (LTM4619) to be 3.3V. See the equation and the table 1 of the datasheet of LTM4619.
R1002: 0.06 ohm 0805, 1%, 1/8 W
- Description: This resistor adjust the circuit-breaker resistor's (Rcb) value. It is in series with the drain (hence RDS(on) of Q1000 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 Q1000 and U1001.
- Specifications/ Calculations: Over-current threshold was calculated assuming input voltage 10V, 90% efficiency and 1.5 of safety factor as follows. {2.2A*3.3V/10V+0.5A*(5V/10V)}*(1.5/0.9)=1.62A Since circuit-breaker trip threshold voltage is 300mV, Rcb has to be 0.185 ohm. (300mV/1.62V=0.185 ohm) and typical value of RDS(on) of Q1000 is 0.125 ohm. R1002 is calculated as follows R1002=0.185-0.125=0.06ohm
- TODO: Value has to be verified
R1003: 43k ohm 0805, 1%, 1/8 W, Cut Tape
Value unchanged from Capstone 2009 [LV2C:GFE:R2253]- Description: R1003 along with Q1001 and Q1002 will "emulate" an overcurrent trigger event as seen by U1001 when an overvoltage at the SPS output trigger event as seen by U1002 or 1003 occurs. See Q1001 and Q1002. When the SPS +3.3 V or 5V output rises above a certain threshold, the output of U1002 or U1003 goes high, turning Q1001 or Q1002 on. When this happens it pulls pin 2 of U1002 or U1003 very close to ground and current flows through R1003 and Q1001 or Q1002. 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 U1001. R1003 limits the extra current pulled through Q1001 and Q1002 when it is turned on.
- Specifications/ Calculations: In normal SPS operation, the voltage drop across Rcb will be less than 300 mV and R1003 is connected to the high impedance pin 2 of U1001 so no current flows through it. If there is an overvoltage trigger event at the SPS output, Q1001 or Q1002 or both are turned on conducting current through R1003 which will have a voltage drop of approximately 300 mV less than the power bus voltage: VR1003 = 16.8 V - 300 mV = 16.5 V. This results in a current boost of about IR1003 = 16.5 V / 47 kohm = 351 uA which is negligible.
R1004: 100 kohm, 0805, 1%, 1/8W, Cut Tape, Value is unchanged from Capstone 2009 [LV2C:GFE:R2218] Rohm, MCR10EZHF1003 (Digi-Key p/n RHM100KCCT-ND $0.38/10) http://www.rohm.com/products/databook/r/pdf/mcr10.pdf.
- Description: 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.
R1005: 19.1k ohm 0805, 1%, 1/8 W
- Description: This is TLV3012AIDBVT (U1002) overvoltage lockout resistor network (R1005, R1007) for SPS output +3.3V. This resistor along with R1007 works as a voltage divider for IN+ (pin3 of U1002) from +3.3 V SPS output rail, and set overvoltage lockout at 3.61V. Resistor value was calculated based on the equation along with figure3 of TLV3012AIDBVT datasheet. We arbitrary set value of R1007 to be 10k ohm to solve for R1005. Divided voltage from +3.3V supply is compared to internal reference voltage (1.242V) of U1002. Output (pin1 of U1002) becomes high when SPS+3.3V ramps up greater than 3.61V. See U1002 for more detail.
R1006: 34k ohm 0805, 1%, 1/8 W
- Description: This is TLV3012AIDBVT (U1003) overvoltage lockout resistor network (R1006, R1008) for SPS output +5V. This resistor along with R1008 works as a voltage divider for IN+ (pin3 of U1003) from +5V SPS output rail, and set overvoltage lockout at 5.46V. Resistor value was calculated based on the equation along with figure3 of TLV3012AIDBVT datasheet. We arbitrary set value of R1008 to be 10k ohm to solve for R1006. Divided voltage from +5V supply is compared to internal reference voltage (1.242V) of U1003. Output (pin1 of U1003) becomes high when SPS+5V ramps up greater than 5.46V. See U1003 for more detail.
R1007: 10k ohm 0805, 1%, 1/8 W
- Description: This is TLV3012AIDBVT (U1002) overvoltage lockout resistor network (R1005, R1007) for SPS output +3.3V. This resistor along with R1005 works as a voltage divider for IN+ (pin3 of U1002) from +3.3 V SPS output rail, and set overvoltage lockout at 3.61V. Resistor value was chosen arbitrary to solve for the resistor value of R1005 using the equation along with figure3 of TLV3012AIDBVT datasheet. Divided voltage from +3.3V supply is compared to internal reference voltage (1.242V) of U1002. Output (pin1 of U1002) becomes high when SPS+3.3V ramps up greater than 3.61V. See U1002 for more detail.
R1008: 10k ohm, 0805, 1%, 1/8 W
- Description: This is TLV3012AIDBVT (U1003) overvoltage lockout resistor network (R1006, R1008) for SPS output +5V. This resistor along with R1006 works as a voltage divider for IN+ (pin3 of U1003) from +5V SPS output rail, and set overvoltage lockout at 5.46V. Resistor value was chosen arbitrary to solve for the resistor value of R1006 using the equation along with figure3 of TLV3012AIDBVT datasheet. Divided voltage from +5V supply is compared to internal reference voltage (1.242V) of U1003. Output (pin1 of U1003) becomes high when SPS+5V ramps up greater than 5.46V. See U1003 for more detail.
R1026:
- Description: 100k ohm pull-down resistor. This resistor pulls Mode/PLLIN pin of UXXXX (LTM4619) to ground while it is starting up. Logic low on this pin enables force continuous operation, and UXXXX operate at switching frequency of 780 kHz until 500 kHz external clock signal from TQM5200 becomes available.
R1103 61.9 kohm, 0805, 1%, 1/8 W, Cut Tape
Value unchanged from Capstone 2009 [LV2C:GFE:R2250]- Description: R1103 is part of the UVLO resistor divider of U1001.
- Specifications/ Calculations: The UVLO voltage was specified to be 9 V. See page 8 and Figure 3 in the MAX5902 datasheet. Letting R1104 = 10.0 kohm and using the typical value of Von/!off = 1.26 V, the UVLO formula from page 8 in the datasheet is R1103 = R1104 * ((VUVLO / (Von/!off)) - 1) = 61.4 kohm. The closet standard value was 61.9 kohm.
R1104: 10 kohm, 0805, 1%, 1/8 W, Cut Tape
Value is unchanged from Capstone 2009 [LV2C:GFE:R2251]- Description: This resistor is one of the UVLO resistor divider of U1001. It set UVLO threshold at 9V.
- Justification: This value is arbitrarily chosen.
Capacitors
C1000:
- Description: 22pF capacitor between Vout1 and Vfb1 of UXXXX (LTM4619). Value of this capacitor was chosen from typical application in the datasheet.
C1001:
- Description: Output capacitor of UXXXX (LTM4619). Value was chosen from datasheet.
C1002: 0.2nF
- Description: This capacitor programs soft-start time of Vout1 of UXXX. 0.2nF was chosen to set soft-start time to be 123us.
C1003:
- Description: Input capacitor of UXXXX (LTM4619) 10uF of minimum capacitance in the datasheet was chosen and it’s decoupled with identical capacitor C1004.
C1004:
- Description: Input capacitor of UXXXX (LTM4619) 10uF of minimum capacitance in the datasheet was chosen and it’s decoupled with identical capacitor C1003.
C1005: Node Power Supply Filter Capacitor Value unchanged from Capstone 2009 [LV2C:GFE:C2206] 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 $0.65/1) http://www.kemet.com/kemet/web/homepage/kechome.nsf/vapubfiles/F3102T491.pdf/$file/F3102T491.pdf.
- Description: C1005 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. TODO: Voltage rating is a bit low.
C1006: Value unchanged from Capstone 2009 [LV2C:GFE:C2207] 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) http://search.murata.co.jp/Ceramy/image/img/PDF/ENG/GRM219R71H334KA88.pdf.
- Description: C1006 is a high frequency noise filter between the power bus and SPS. It did not have to have as high a capacitance as C1005 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 C1005.
C1007:
- Description: 22pF capacitor between Vout2 and Vfb2 of UXXXX (LTM4619). Value of this capacitor was chosen from typical application in the datasheet.
C1008: 100uF Output capacitor of UXXXX (LTM4619).
Value was chosen from datasheet.C1009: 0.2nF
- Description: This capacitor programs soft-start time of Vout2 of UXXX. 0.2nF was chosen to set soft-start time to be 123us.
C1010: 2.7 uF, 10 V, 0805, X5R, Cut Tape, RoHS Compliant, Kemet
C0805C275K8PACTU (Digi-Key p/n 399-3127-1-ND $7.02/10)
Value is unchanged from Capstone2009 [LV2C:GFE:C1010]- Description: This is a TLV3012AIDBVT "Secondary Power Supply" Cap (C1010). This capacitor prevent U1002 from power cycling by acting like an instant power supply for U1002 when SPS-output drops down by certain level.
- Justification: 2.7uF capacitor ensures U1002 powered more than 0.5s when SPS-output drops by 1V. See Capstone 2009 [LV2C:GFE:C1010] for more detail.
C1011: 15 nF TLV3012AIDBVT Overvoltage Detection Cap
Value is unchanged from Capstone 2009 [LV2C:GFE: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)
See [LV2C:GFE:C2251] for more detail.C1012:2.7 uF, 10 V, 0805, X5R, Cut Tape, TLV3012AIDBVT "Secondary Power Supply" Cap (C1010)
RoHS Compliant, Kemet, C0805C275K8PACTU (Digi-Key p/n 399-3127-1-ND $7.02/10) http://www.kemet.com/kemet/web/homepage/kechome.nsf/vapubfiles/F3102X5R.pdf/$file/F3102X5R.pdf.- Description: This capacitor prevent U1003 from power cycling by acting like an instant power supply for U1003. Value is the same as corresponding capacitor in [Capstone2009 LV2C:GFE:C2250]
C1013: 15 nF TLV3012AIDBVT Overvoltage Detection Cap
Value is unchanged from Capstone 2009 [LV2C:GFE: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) http://rocky.Digi-Key.com/WebLib/AVX/Web%20Data/X7R%20(C).pdf.
See [LV2C:GFE:C2251] for more detail.C1031: 100nF Noise filtering capacitor for U1009(Dflip-flops)
C1032: 100nF Noise filtering capacitor for U1010(divide by 12)
others
L1000: Power Bus input Choke
Part Description: CMS2-4-R Common Mode Inductors 102 uH, Micro-PAC Plus Package, RoHS Compliant, Cut Tape, (Digi-Key p/n: 513-1115-1-ND, $3.37/1).- Description: : 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 *Note: (CMS1-11-R) has gone non-stock at Digi-Key and replacements are available in lots of 2000. New suggested part(CMS1-7-R) is dissimilar in value, but same physical size.
F1000: Node Power Supply Fuse
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) http://documents.tycoelectronics.com/commerce/DocumentDelivery/DDEController?Action=srchrtrv&DocNm=SCD25801&DocType=CD&DocLang=EN- Description: 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 U1001's job.
- TODO: verify current rating
TVS1000: the same part from capstone 2009 [LV2C:GFE:TVS2201] was used.
18 V, SMB, Unidirectional, Cut Tape, RoHS Non-Compliant, Diodes Inc, SMBJ18A-13 (Digi-Key p/n SMBJ18ADICT-ND $0.89/1) http://www.diodes.com/datasheets/ds19002.pdf.- Description: A transient voltage suppressor (TVS), this "zener like" diode protects the SPS 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, F1000. That is what we want.
*Note: . The original capstone2006 part is no longer available in Digi-Key. Re-specify or find new vendor. One suggested replacement is B72500D200A60V7 (Digi-Key p/n: 495-3413-1-ND $0.20/1) http://www.epcos.com/inf/75/ds/cd_standard.pdf This is a simple Zener type ESD suppressor in an 0603 package.
Another replacement possibility is: V2F118C400Y1FDP, Digi-Key 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.
- Description: A transient voltage suppressor (TVS), this "zener like" diode protects the SPS 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, F1000. That is what we want.
*Note: . The original capstone2006 part is no longer available in Digi-Key. Re-specify or find new vendor. One suggested replacement is B72500D200A60V7 (Digi-Key p/n: 495-3413-1-ND $0.20/1) http://www.epcos.com/inf/75/ds/cd_standard.pdf This is a simple Zener type ESD suppressor in an 0603 package.
Q1000: The same part from capstone 2009 [LV2C:GFE:Q2250] was Selected
-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)- Description: This PMOS works as circuit breaker controlled by U1001. RDS(on) of saturated Q1000 is used by U1001 to sense current flowing on power line. See capstone 2009 [LV2C:GFE:Q2250]
Q1001: The same part from capstone 2009 [LV2C:GFE:Q2251] was Selected
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) http://rocky.Digi-Key.com/WebLib/Infineon/Web%20Data/BSS123.pdf.- Description: • This Mosfet is off under normal operation, but in the event SPS-5V output exceeds 5.46V, it is turned on by U1002 (comparator sensing overvoltage). Then pin2 (Drain) of U1001 becomes almost ground, and Q1000 shut off current.
Q1002: The same part from capstone 2009 [LV2C:GFE:Q2251] was Selected
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) http://rocky.Digi-Key.com/WebLib/Infineon/Web%20Data/BSS123.pdf.- Description: This Mosfet is off under normal operation, but in the event SPS-3.3V output exceeds 3.6V, it is turned on by U1002 (comparator sensing overvoltage). Then pin2 (Drain) of U1001 becomes almost ground, and Q1000 shut off current.
CR1000: TLV3012AIDBVT "Secondary Power Supply" Schottky Diode
The same part with capstone 2009 [LV2C:GFE:CR2250] was selected
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)CR1001: TLV3012AIDBVT "Secondary Power Supply" Schottky Diode
The same part with capstone 2009 [LV2C:GFE:CR2250] was selected
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)