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AMC1311-Q1: AMC1311-Q1 power off , we measurement Vout voltage difference was not zero.

Lawrence He
Genius 3280 points
Part Number: AMC1311-Q1
Other Parts Discussed in Thread: TPS7A16A-Q1

Dear,


We use AMC1311-Q1, and we find some question:

if we power off and we measurement  VOUTP、VOUTN (C84) have 2.5V voltage difference, it's will effect Next stage OPA.

schematic as below

96V check.pdf

If any suggestion, Please advise me.

Thanks,

Best regards,

Lawrence.

  • 0
    TI__Mastermind 49111 points

    Hi Lawrence,

    I assume by power off you mean that the high side supply VDD1 is powered down?

    If so, you're seeing the fail-safe output as outlined in section 8.3.3 Fail-Safe Output of the datasheet. This function is intended to notify the MCU that the high-side supply is missing and to take action accordingly to protect the system. This Fail-safe voltage is slightly beyond the clipping voltage.

  • 0 in reply to Alexander Smith
    Genius 3280 points

    Hi, Alex

    so you mean, if we power down the system,  also need keep VDD1 voltage?

    so that our MCU will do not read voltage difference. is right?


    we find TPS7A16A-Q1 maybe can supply to VDD1 of AMC1311B-Q1  ,  it`s good choose?

    if any suggestion, please advise me.

    Thanks,

    Best regards,

    Lawrence.

  • 0 in reply to Lawrence He
    TI__Mastermind 49111 points

    Hi Lawrence, 

    If VDD1 goes down, then the device will show the fail-safe output (provided that VDD2 still has power).

    That is one option, I'm not familiar with this regulator - so you may want to ask that forum if it's appropriate or not.

    The other option is to have the MCU recognize the fail-safe output and use this notification to protect the system, which is the intended use for this function. If you keep VDD1 powered up at all times then the device will not show the fail-safe output.