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TPA3221EVM: TPA3221EVM current of PVDD behavior issue

Part Number: TPA3221EVM

Hi Team,

We have measured TPA3221EVM startup timing for Current(from power supply to PVDD), PVDD, FAULT, and OUT1_P.

We found that there is negative current at start. It was so strange and confused us. And there were several inrush current(red circle) before OUT switching.

Is it a normal behavior of this IC? We would like to learn what reason causes it.

Could you help us to explain the phenomenon of inrush current?

Roy

  • Hi Roy,

    First of all, the behavior of OUT1_P before the switching starts is actually PPSC detection. You may find more details on section 9.4.5.4 on the datasheet.

    Secondly,  looks like the waveform is missing the red circle you mentioned. The current scale is too small, could you change it to at least 200mA? Usually, the inrush current during PVDD setting up is mostly charging the bulk capacitance.

    Thanks!

    Regards,

    Sam

  • Sam,

    Thanks for information. Is PPSC frequently? I think the inrush is frequently. As you said, the behavior may occurred by PPSC. I would like to check if there is anything could indicate it. 

    Roy

  • Hi,

    The PPSC could be identified by OUTx pin behavior. The PVDD current is scaled to only 10mA. Such small PVDD "inrush" current should not cause any problem.

    You may also monitor the other OUTx pins. Maybe the current spikes appears by other output legs doing PPSC detection.

    Thanks!

    Regards,

    Sam

  • Hi Sam,

    I attach more fig as below.

    The time scale is 100ms per grid. The negative current is in the red circle and it is about 300mA. Do you think the negative current is from inrush current?

    Regards,

    Roy

  • Hi Roy,

    It's more like the spike is caused by the power supply dynamic response. You may monitor the current between the PVDD pin and the PVDD capacitor. Such kind of negative current pulse should not happens.

    Thanks!

    Regards,

    Sam