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TPS7A8001 power down waveform

Vincent Li
Prodigy 150 points
Other Parts Discussed in Thread: TPS7A8001DRBEVM

Hello,

Does anyone help to explain why Vout goes down with a step(marked in red) when Vin and EN is down? And why after the step Vout is going to 0V very fast?

 

Thanks

Vincent

  • 0
    TI__Mastermind 41770 points

    Hi Vincent,

    How is this measurement tested and what is on the load? We will need more information. Just from guessing, it looks like a different discharge profile, probably from the load turning off at that voltage? The large step is the LDO reaching is UVLO and shutting down. Does the customer have a problem with the little bend? If the LDO is disabled before dropping vin, you can get a more monotonic shutdown.

    Regards,

    Darwin

  • 0 in reply to Darwin Fernandez
    TI__Prodigy 150 points

    Hello Darwin,

      This waveform was tested on TPS7A8001DRBEVM. EN is connceted to VIN. VIN=5V, VOUT=3.3V with static loading 1A. I suspect the bend show LDO is in the dropout region where VOUT is proportionally following VIN and the large step is in the off region. Correct?

     ' If the LDO is disabled before dropping vin, you can get a more monotonic shutdown.' From the datasheet as below, should the LDO be disabled when EN is lower than 0.4V?

    Enable high (enabled) Min 1.35V

    Enable low (shutdown) Min 0V , Max 0.4V

     

    Thanks

    Vincent

  • 0 in reply to Vincent Li
    TI__Mastermind 41770 points

    Hi Vincent,

    Yes, EN is shutdown when VEN is below 0.4V. Please see below shutdown waveform.

    2084.tps7a8101e_4v_3.tif