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TPS746-Q1: Shutdown from Enable

Ray Tong
Intellectual 1330 points

Part Number: TPS746-Q1

Could you please provide the Shutdown from Enable timing diagram of TPS74601?

The picture below shows the power-on and power-off test chart of the TPS74601 power supply. The power-off time is much longer than the power-on time, about 1.85ms.

Please help analyze whether it is normal？

  • 0
    TI__Expert 4790 points

    Hi Ray,

    There is no turn off time spec.

    The turn off time depends on the output cap used, the current being drawn, and output pull-down, if present in the part.

    Since all these factors affect turn off time, it is normal for the turn-off time to differ from the turn-on time.

    Also, turn-on time is controlled by a circuit and turn-off time is mostly system dependent.

    Best Regards,

    Bobby

  • 0 in reply to Bobby
    TI__Intellectual 1330 points

    HI Bobby，

    Thank you for your answer. The customer wants to shorten the drop time of en, what improvements can be made?

    I have already sent the client's schematic diagram to your email

    Best Regards,

    Ray

  • +1 in reply to Ray Tong
    TI__Expert 4790 points

    Hi Ray,

    Reducing the value of output cap will help shorten the turn off time.

    If this is not possible, a resistor can be put in parallel with Cout(but that would decrease efficiency by dissipating power all the time). 

    So, you could add a switch to discharge the Cout through a resistor. Take the Enable signal, invert it, and then drive a transistor with a resistor in series.

    Best Regards,

    Bobby