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LM74810EVM: TVS Selection Question/Confirmation

Darren Osborne
Prodigy 30 points
Part Number: LM74810EVM

Tool/software:

Hi TI Forum,

I have designed the following circuit (below), but I'm not totally confident regarding the TVS selection and/or my understanding of the datasheet. I was hoping this could be validated and if incorrect, suggest how I can correctly implement it(?). Please note, BATT is just a standard Li-Ion 40V battery.

7608.LM74810.pdf

1) Is my setup of two uni-directional diodes ok? Is it possible to just use one bi-directional diode without losing RPP functionality?

2) It was very difficult to find a diode that meets both the working/clamping voltages. Hence, I 'assume' given that it's only for transient conditions, a clamping voltage of 69.8V (just 0.2V under the device maximum) is 'ok'?

3) What is the likely output current of SW? The op-amp has I(max) of 5mA (Vin+/Vin-), hence I added a 1kOhm resistor, but is this needed?

4) Is there anything else that I've forgotten?

Many thanks,

Darren

  • 0
    TI__Mastermind 26065 points

    Hi Darren,

    1. Using a bidirectional diode is important here otherwise during RPP, the battery will be shorted via diode D1. Adding a negative side TVS or Schottky will block it.

    2. What is the level of transients that you expect? We usually don't use any TVS for positive side transients blocking in automotive use case. We use it to block the power path through TVS- and use the other TVS for negative transients.

    3. The current through SW pin will be dependent on resistor values. There is nothing to limit the current.

    4. The schematic looks fine.

    Regards,

    Shiven Dhir