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TCA6408A: Gut check: driving MOSFETs

Jeffrey Blum
Prodigy 110 points

Part Number: TCA6408A
Other Parts Discussed in Thread: CSD17571Q2, UCC27517

Tool/software:

Maybe it's just late and I'm tired, but I just want to check myself here. Can you use the I/O pins of the TC6408A to directly drive MOSFETs (specifically the CSD17571Q2)?

  • 0
    Guru 320660 points

    When the load is a large capacitance, it looks like a short and can exceed the absolute maximum ratings for the output current.

    Logic outputs are designed for loads of up to about 70 pF. The CSD17571Q2's input capacitance is 360 pF.

    When you do not need to switch quickly, insert a current-limiting resistor in series with the gate. If you do need to switch quickly, use a stronger driver, e.g., a gate driver like the UCC27517.

  • 0 in reply to Clemens Ladisch
    Prodigy 110 points

    Right, I forgot to mention the 100ohm resistors I put between the driver and the FETs for that exact reason. These are just on-off switches so speed is not a concern.

  • +1 in reply to Jeffrey Blum
    TI__Guru 56688 points

    Hi Jeffrey,

    Then I believe your implementation is okay with 100 ohm current limiting resistors. 

    Recommended operating is +/-25mA of current from the output pin. Abs. max is +/-50mA but it is preferred that the device operating in the recommended operating for best performance and security that the device won't be damaged. 

    Regards,

    Tyler