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TPS568215: SoftStart Time

T Kishi
Genius 4425 points
Part Number: TPS568215
Other Parts Discussed in Thread: TPS562219A,

Hi

My Customer has question.

Is it safe to set the soft start time of TPS 568215 to 100 ms?

It is necessary to set a delay time by spec request

Best Regard 

T Kishi

  • 0
    TI__Mastermind 33765 points

    Hi,

    I will check it with designer and update you later.

  • 0
    TI__Expert 5745 points
    Why customer want such long ss time?
    The long ss time may result in the circuit couldn't start up, what the condition of the customer, i more information to check it and get more information from designer.
  • 0 in reply to Vental Mao
    Genius 4425 points

    Thank you for confirmation.

    This question is related to this article.

    ⇒

    Customers need to such a sequence.

    Sequence.pdf

    If there is a delay time with TPS562219A at the time of an instantaneous power failure,can not keep Sequence.

    I thought it could be adjusted by TPS568215 soft start.

    Device change is not possible,is there any idea?

    Regard

  • 0 in reply to T Kishi
    TI__Expert 5745 points
    Please send email about all the schematic and layout to me and Andy.
    The 19ms seems that the EN rising time, please take a look of the EN pin's waveform
  • 0 in reply to Vental Mao
    Genius 4425 points

    Thank you for your response.

    I will ask schematic and layout to the customer.

    I checked with TPS 562219AEVM.
    A delay time of about 19 ms could be confirmed.

    TPS562219A_EVM.pdf

    regard

  • 0 in reply to T Kishi
    TI__Expert 5745 points
    How do the generate this glitch on Vin? Please send me the email, i can't find your email in infolink, thank you!
  • 0 in reply to Vental Mao
    TI__Expert 4875 points
    Hi,

    We did not check this kind of quick power off behavior on TPS562219A before. But I think I got some clue here for you.

    First of all, do you think that the Vin during power off goes lower to UVLO threshold? The lowest UVLO for TPS562219A could be lower than 3V. In your waveform, I could not tell whether it is lower than 3V. It also applies to EN. Considering the accuracy of your channel, it is questionable that Vin actually goes to UVLO.

    Secondly, why only output 5V has this issue. It is because that with input goes down, input voltage could be close or lower than 5V. The device will work under max duty and the output voltage will out of regulation. There is no way that output voltage will stay at 5V and output voltage will drop to below UVP threshold. The UVP protection will work and device will enter into hiccup mode. It is what you describe as delay time. For output of 3.3V and 1V, the device will not need to work with max duty and output voltage could still be regulated. UVP will not triggered and delay time is not observed. Thanks!