Page Comparison

• todo

  • cheaper than COTS efuse board for initial power up

• use case

  • ground validation

• why

  • maybe cheaper than COTS

  • fun

• who

  • unassigned

• timeline

  • no efs effort

  • deprioritized for now

...

• Will use a 5V supply, mainly due to the current sense circuitry (nominal supply voltage of the amp is 5V)

• Linear Regulator (instead of switching because low noise - for sense circuitry, and circuit consumes barely any power, will show in power analysis here) (query)
  Might cascade regulators to reduce power dissipated per regulator (if heating is an issue). Could also put diodes (or power resistor) in series with regulator input to reduce drop-out voltage, and consequently power dissipated by regulator.

  • ZXTR2005Z-13 Diodes Incorporated | Integrated Circuits (ICs) | DigiKey, 100V max, 38mA max, $0.81

    • The maximum junction to ambient thermal resistance is 112C/W (measured on 15mm x 15mm 1oz copper). If we operate on a really hot day (40C), and want the chip to rise up to no more than 70C (to be relatively safe to touch), the maximum power the regulator should dissipate is (70-40)/112 = 0.268W. In the worst case, with 12S LiPo, this means a maximum current of 0.268/(50.4-5) = 5.9mA.

  • ZXTR1005K4-13 Diodes Incorporated | Integrated Circuits (ICs) | DigiKey, 100V max, 50mA max, $1.05

...

• Fault LED (RED)

  • Red when RST switch is closed and when overcurrent fault is detected

• ON LED (GREEN)

  • Green when RST switch is open and when no overcurrent fault is present

• Both of the LEDs above will only be on if the 5V regulator is working, so they can be used as power indicators.

• APHB1608LCGKSURKC Kingbright | Optoelectronics | DigiKey (Red and Green LEDs in one package)

• Separate red & green LEDs.

• The two-in-one comparator can drive them in the following configuration

  

Switches

• Is debouncing needed for each switch?

  • No, debouncing will only result in additional delay with the switch configurations I’ve planned for. Having smooth switching doesn’t seem to be necessary in this project.

• ON/RESET DPST/DPDT switch (query)

  

  • SLW-826947-5A-RA-D CUI Devices | Switches | DigiKey

• If delay circuit uses different capacitor options (to vary the RC time constant of the fault line output), will need a… SP3T switch?

  

  • CUS-13TB Nidec Components Corporation | Switches | DigiKey; Surface mount

  • SLW-1516255-6A-RA-D CUI Devices | Switches | DigiKey; Through hole

...

• INA381 (current sense chip): 450uA

• Threshold Current Dividers and pull-up resistors: max 2mA

• Comparator Quiescent Current: max 50uA

• LEDs: 5.9-(the above) = 4.4mA max

  • As only 2 LEDs are needed, and only one should be powered on at once, the 2mA LEDs should work great being powered off of the 5V regulator.

COST ANALYSIS

For buying every component (not including the majority of passives or the XT connectors) at the per-unit price, the cost is $7.22 per board. For reference, OTS is $12.99/board. This seems pretty reasonable.