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TPS22968-Q1: 20ms OV transient

John Fedak
Expert 6715 points
Part Number: TPS22968-Q1

Hi Team,

Good morning, my customer is using the TPS22968-Q1 in an older design and they have found a fault condition where the input regulator can spike to 6.5V for 20mS.

Do we have any previous test data for if the device could handle this?

This is over the abs max of 6V given in the datasheet, so I understand that it cannot be guaranteed.

Regards,

~John

  • 0
    TI__Genius 15740 points

    Hi John,

    I have a few questions for clarification:

    1. Is the 6.5V transient on VIN or VBIAS?
    2. Is the SWITCH in the ON or OFF state when the transient occurs?
    3. How often will this 20ms spike occur in the device operating life?

    Thanks,

    Alek Kaknevicius

  • 0 in reply to Aleksandras_Kaknevicius
    TI__Expert 6715 points
    Hi Alek,

    Thank you for the quick response, the customer has let me know:
    1. VBIAS
    2. ON
    3. Very Rare

    Regards,
    ~John
  • 0 in reply to John Fedak
    TI__Genius 15740 points

    Hi John,

    The risk here is that the ESD cell on the VBIAS pin may trigger due to the transient on VBIAS. If 6.5V is applied very quickly, there is a chance that the ESD cell could potentially draw a large amount of current and damage itself.

    I did some testing with a device and found that slowly bringing up the voltage to 7.5V did not draw a large amount of current and did not cause any device damage. However, this is untested across a large sample size of units and not tested over temperature. Also, this was not a fast transient that caused the ESD cell to trigger at a lower voltage.

    Do you have an idea of what the voltage spike profile looks like? What is the initial (stable) voltage and how quickly does it ramp up?

    Thanks,

    Alek Kaknevicius

  • 0 in reply to Aleksandras_Kaknevicius
    TI__Expert 6715 points

    Hi Alek,

    Thank you for testing this in the lab and your feedback.

    I have received these profiles from the customer on the spike that is being seen:

    Given the spike on the left side - the rise from 5.3 to 6.3V is very fast. My guess is that this could trigger the ESD cell?

    Regards,

    ~John

  • 0 in reply to John Fedak
    TI__Genius 15740 points

    Hi John,

    It's hard to tell with the left scope shot because it is not very zoomed in, but the ramp from 5.3V to 6.3V does look pretty quick. If fast enough, this does have the potential to trigger the ESD cell and cause a large amount of current to flow through the device. Also, I'm not sure if zooming in will cause the voltage to be a bit higher, but if this is the case then the probability for this event is even higher. Luckily, the second scope shot looks a lot slower, and there is less risk.

    Because this is above 6V, we cannot guarantee what will happen. However, if the customer tests these conditions across a few units across temperature then they will have a reasonable expectation of what the device can handle in their system.

    Thanks,

    Alek Kaknevicius