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TPS717: Recover from UVLO

Takashi Onawa
Genius 13200 points
Part Number: TPS717

Hi Team,

My customer plan to use TPS71701 in their one of app and they have a stuck issue now.
When performing a test to toggle Vin as a stress test, Vout sometimes stays low  even though Vin was back to 5V.
According to TPS717 datasheet, this device has 3 mode, so they think it's stuck in “Disable mode” for some reason.

Then, they have a question as follow.

1. Is it possible to enter Disable mode even though 5V is applied to Vin and EN and Tj<125C?

1. What is a trigger of mode transition in this device? 

Regards,

Takashi Onawa

  • 0
    TI__Mastermind 23361 points

    Hi Onawa-san, 

    To better understand the issue, will you provide some waveforms that show the voltage change on Vin, Vout and En when the stuck happens? I am not aware that this device requires certain sequencing during powering on, but it would be really helpful if you could provide more details for us to investigate. 

    Regards, 

    Jason Song

  • 0 in reply to Jason Song
    TI__Genius 13200 points

    Hi Jason-san,

    OK, I will send you the data offline, which I get from the customer .
    According to the customer, the issue only see on adjustable version(TPS71701).

    When 5V is applied again to Vin before Vin is discharged to 1V or less, Output looks stuck.
    So I recommended them to add strong pull down at EN pin for quick discharge. It seems that  The workaround has almost solved the issue.

    But they need to write a report to close this issue completely.

    This is a background of the questions below, so could you give me some comments for the questions below also?

    1. Is it possible to enter Disable mode even though 5V is applied to Vin and EN and Tj<125C?

    2. What is a trigger of mode transition in this device? 

    Regards,

    Takashi Onawa

  • 0 in reply to Takashi Onawa
    TI__Mastermind 23361 points

    Hi Onawa-san,

    Based on the information you provided, it seems that the device with the stuck output has been damaged. The damage is likely to happen during the powering-down cycle with output voltage higher than input voltage. Can you work with the customer to provide scope-shots with Vin, Enable, Vout during their power down sequence? The scope shot will help us to know if Vout can be temporarily higher than Vin during the power down cycle.This device is susceptible to reverse current, and some of them may be more susceptible than others.

    Since this issue is continued to support by direct emails. I am closing this post.

    Regards,
    Jason Song