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TPS53317: TPS53317 / Power up sequence

S.Satoshi
Guru 21675 points
Part Number: TPS53317

Hi,

Please let me ask about power up sequence of tracking configuration.

I understand that the recommended sequence should power up EN and V5IN first and then power up REFIN. But now REFIN start up first at customer's test board because the softstart time of EN and V5IN is too slow as attached. So I'd like to know what abnormal behavior will be happened with this incorrect sequence.

Of course they will fix this sequence at next proto type board. 

Best Regards,

Satoshi / Japan Disty

  • 0
    TI__Mastermind 24075 points

    Hi Satoshi,

    In customer's case, the part will do non-tracking startup, like the waveform in datasheet figure 18.

    Thanks

    Qian

  • 0 in reply to Qian Chen
    Guru 21675 points

    Hi, Qian,

    Thank you for your comment.

    Regarding Fig18, I think that this is the case of the same power up timing of EN/V5IN and REFIN. Now I'm taling about REFIN first and EN/V5IN after that. Do you mean that my situation should be the same with Fig 18?

    Best Regards,

    Satoshi / Japan Disty

  • 0 in reply to S.Satoshi
    TI__Mastermind 24075 points
    Hi Satoshi,

    Yes, I think your situation should be the same as Fig 18.
    Vout will rise up with a fixed 1.6ms soft start time after V5IN and EN voltage are above their threshold.


    Thansk
    Qian
  • 0 in reply to Qian Chen
    Guru 21675 points

    Hi Qian,

    Thank you for your support. Please let me ask again about start up sequence at tracking startup.

    From Fig 21, I understand that it's recommended that REFIN should be start up after 260us min after VREF is stabled. Then what concern do you think if the REFIN start up within 260us after VREF is stabled as attached?

    Best Regards,

    Satoshi / Japan Disty

  • 0 in reply to S.Satoshi
    TI__Mastermind 24075 points

    Hi Satohi,

    During 260us delay time, TPS53317 will check if REFIN votlage rise up or not.

    If REFIN voltage already rise up, the part will do non-tracking startup as shown in figure 18.

    If REFIN voltage is 0V, the part will do tracking startup as shown in figure 21.

    If REFIN voltage starts to rise up during 260us delay time as it is shown in concerning case, the part may do "non-tracking startup" or tracking startup".

    Thanks

    Qian

  • 0 in reply to Qian Chen
    Guru 21675 points

    Hi Qian,

    Thank you for your quick response. I understand that this situation will not be cause of abnormal operation or power up failure.

    Best Regards,

    Satoshi / Japan Disty