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

...

• Customizable current threshold Customizable current shut-off delay (I think I can design for 1A, 2A and 3A)

• Customizable current shut-off delay (not really clear if these are exact or maximum delays in the OTS device)

• Fault indicator LEDs

• Manual ON/OFF/RESET switches

• $12.99 VIFLY, >$40 on Amazon

...

Reverse Voltage Protection:

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• PMOS

  • SQJ479EP-T1_GE3 Vishay Siliconix | Discrete Semiconductor Products | DigiKey (query)

    • $1.70; Probably too expensive

    • 33mOhm @10A (Overkill?);

      Image Modified

    • 80V max VDS

    • +-20V VGS; 10V min RdsON → choose a ~10-15V zener diode

  • GSFD500P10 Good-Ark Semiconductor | Discrete Semiconductor Products | DigiKey

    • $0.99

    • 50mOhm @15A

      Image Added

    • 100V max VDS

    • +/-20V VGSmax;

    • This results in a maximum voltage drop of 105mV across the PMOS (when conducting 3A)

• Zener diode (query)

  • MM5Z12VT1G onsemi | Discrete Semiconductor Products | DigiKey

    • Rated watts 0.5W; Rated current ~41.67mA @12V

    • Specs

      

• Pull-down resistor

  • Size it to result in <41.67mA (rated zener current) of current going through the zener, whilst being >1mA (the reverse current of the zener)

    • Worst-case supply voltage is 4.2*12=50.4V, so resistance needs to be at least (50.4-11.4)/0.04167=936Ohms.

    • Lowest supply voltage is 3.2*6=19.2V (if using 6S config), and to pass at least 1mA of current through the zener, the resistance needs to be at most (19.2-12.7)/0.001=6.5kOhm

    • I will thus choose 3.5kOhm.

...

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

• LDO Linear Regulator (instead of switching because low noise, 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.

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

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

Response Delay Circuitry:

• RC circuit at INA381’s current sense output of INA381 fault line (high when overcurrent fault occurs).line

  Image Added

  • C adjustable with multiple capacitors and a switch, or a varistor.

  • R fixed or a pot

  • Need to ensure amp output is capable of driving this circuit (choose proper filter resistor)

  • Since the output of the external comparator amp will only be the rail (at steady state; it will be delayed according to the time constant), the internal comparator will compare the ext. comp. with a constant voltage. I arbirtarily chose 63% of Vdd, as this will give a delay equal to the time constant.

  • MCP6541T-I/LT Microchip Technology | Integrated Circuits (ICs) | DigiKey

    • Low power consuming comparator. High output current (overkill)

• Counter + Oscillator circuit (counter query, osc query) - Probably overkill, too expensive, and too expensivepower consuming for a simple LDO.

  • when certain counter value is obtained (which counts only when amp output reaches some threshold value → need an external comparator for this), comparator is tripped (after a fixed amount of time, which can be either programmed, or comparator looks at a different counter bit for a different delay: i.e. less significant bit for smaller delay, more significant for longer delay)

...

• Fault LED

• Power LED (LDO output good)

• Ready LED (safety NMOS is no longer controlled by ready switch)??

  • Maybe in the off state, the ready switch can turn off safety NMOS (infinite Rds) and reset the latch. Maybe it should be called the RESET switch instead

Switches

• Is debouncing needed for each switch?

• RESET-READY 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

POWER ANALYSIS

COST ANALYSIS