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TPS650864: TPS650864 damaged buck rail after power on

Giulio Zoppi
Intellectual 645 points
Part Number: TPS650864

Hello, 

We are working with a system in which a TPS650864 is exploited to supply a XCZU3CG SOC.

We've had two episodes of PMIC damaged at power-on in one year. 

In the second episode the damage involves only Buck4 which generates 3.3V. The PMIC is supplied by a 12V pre-regulator which we suspect is the responsible of the failure.

Do you have any recommendation concerning the characteristic of the input voltage and the slope it must be applied?

Best regards, 

GZ

  • 0
    TI__Mastermind 18650 points

    Hi Giulio,

    Let me check some of our documentation on this part and get back to you early tomorrow (CST).

    Regards,

    James

  • 0 in reply to James Steenbock
    Intellectual 645 points

    thank you, James!!!

  • 0 in reply to Giulio Zoppi
    TI__Mastermind 18650 points

    Hi Giulio,

    I'm not seeing any major constraints on the PVIN4 input voltage slope. I would need to know more about the actual failure itself to even hazard a meaningful guess as to the damage source.

    Normally the PVINx inputs come from either BUCK1 in a 5V configuration or some external power source in the range of 3.3V - 5V so as far as I know BUCK4 should be somewhat distant from 12V VIN considerations.

    If a deeper look is necessary I would reach out to customer service about our device return process, just to see what your options are.

    Our recommendations on IC usage are all contained in the datasheet with some additional application notes on the product page.

    Regards,

    James

  • 0 in reply to James Steenbock
    Intellectual 645 points

    Hello, James. 

    thank you again for your support. 

    Our system is part of a multi-site equipment that is meant to be attached to a proprietary hub.  we have no easy access to our device when it is plugged to the hub, so we are guessing what happens here.

    The attached picture shows a simplified schematic of the PMIC section of our system from the proprietary hub all the way up to the PMIC.

    The PMIC is supplied by a 24 to 12V pre regulator with no SS capacitor (this portion of the schematic is under revision though).

    It seems that the 24V is hard switched to the pre-regulator, and we have no idea about the pre-regulator's input transient when the site is engaged. 

    Thank you for your valuable support and have a great weekend.

    Regards, 

    Giulio

  • 0 in reply to Giulio Zoppi
    TI__Mastermind 18650 points

    Hi Giulio,

    Understood. If you have any other questions about the PMIC just let us know here on E2E!

    Regards,

    James

  • 0 in reply to James Steenbock
    Intellectual 645 points

    So, is it likely for you that the hard switching of the 24V might have caused the damaging of just one rail?

    Regards, 

    G 

  • 0 in reply to Giulio Zoppi
    TI__Mastermind 18650 points

    Hi Giulio,

    It's hard to say without a deeper analysis but the VSYS pin of the device has a max recommended operation limit of 21V.

    The absolute max rating of the VSYS pin is 28V so I wouldn't expect 24V to cause physical damage on the package. If a large amount of energy was dumped into the input it might be possible that it founds its way to the BUCK4 SW node and caused damage but I feel like this is unlikely. Also, I don't think a fast 12V transient would cause damage unless there was a large current spike to accompany it.

    The results of EOS (electrical over-stress) can vary depending on the initial conditions of the device.

    You mentioned that this has happened twice in one year. Is this the first year of your production? What is the ratio of damaged PMICs to good units?

    If you are doing a schematic redesign, I highly recommend using the TPS65086x Schematic and Layout Checklist (Rev. A) as you go to make sure all the recommended pin connections are considered.

    Regards,

    James

  • 0 in reply to James Steenbock
    Intellectual 645 points

    Thank you, James, 

    We are in a prototypal phase, with a limited number of devices; this is the first time we plug the device to the hub where it is supposed to be plugged in.  

    The first damaging event happened months ago: the device had been plugged to the bench supply fully on. Back then all the PMIC's rails got damaged.

    We are supposing that something similar happened because of the correlation of the two events.

    For the rest, we haven't had problems during system bring-up and validation, even during intensive usage.

    Regards,  

    Giulio

  • 0 in reply to Giulio Zoppi
    TI__Mastermind 18650 points

    Hi Giulio,

    Unfortunately, there's not much I can say without a clear look at the signals being experience by the PMIC at power up. If all the PMIC outputs got damaged in one instance that seems like a case of major EOS. It could be a result of some kind of hot plugging action if you are inserting the boards into a hub.

    Regards,

    James

  • 0 in reply to James Steenbock
    Intellectual 645 points

    Thank you, James!!!