• State Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 193 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS7H4010-SEP: PGOOD immunity to failure on power transistors

Jean-Irénée Hullo
Prodigy 30 points
Part Number: TPS7H4010-SEP

Hi,

I'm using the TPS7H4010-SEP in a new design. 

We are at the stage of architecture, and studying the effect of single point of failure of the component. 

If we consider a failure of High side or Low side transistor (for exemple in short circuit), can we consider the PGOOD is immune to propagation and remain functionnal ? Maybe the function is segregated on the chip?

Do you have any data or recommandation for this case to study ?

The main idea is to use the detection (by PGOOD state) of  an Over voltage or Undervoltage on the output in case of failure to passivate it. 

Thankyou in advance for your help

Best regards 

Jean-Irénée Hullo

Power & Analog Designer

  • 0
    TI__Genius 14540 points

    Bonjour Jean-Irénée,

    The PGOOD circuit simply monitors the VOUT voltage via feedback voltage (pin FB), and responds when the low or high voltage thresholds are crossed.  So if a fault condition causes VOUT to cross these thresholds, then PGOOD will follow.  I have confirmed on other buck converters in our portfolio, not this one specifically, that PGOOD de-asserts when the high side current limit is invoked and VOUT starts to drop as result. So yes, PGOOD should be used to monitor the 'health' of the output.

    Thanks

    Christian

  • 0 in reply to Christian Yots
    Prodigy 30 points

    Hello Christian,

    Thank you a lot for the answer

    i am missing some information though, the main idea was indeed to use the pgood to monitor the health of the output 

    I want to be sure (for failure mode analysis) that in case of failure of the TPS7H4010 (precisely internal mosfets in short circuit), we can count on the PGOOD information. The ECSS norm  tells us to avoid to use the protection of an IC to protect us against failure of the IC.

    So, do you have some counter arguments against their recommandation ? Do you have a failure mode analysis of the IC that says that PGOOD is still functionnal in case of failure ? Did you take some precautions to avoid the propagation of a failure in Mosfet to pgood detection circuit ? 

    Thanks 

    Jean-Irénée

  • 0 in reply to Jean-Irénée Hullo
    TI__Genius 14540 points

    Hi again,

    Ok i now understand your concern.  In general this is probably a good rule of thumb to adhere to- don't use the protective circuits of device against a failure of that same device.  I assumed an overcurrent fault in which the device responded as designed to limit current until the fault is removed.  I have seen PGOOD behave as expected when different faults are presented.  In one case, where the fault is very close to the current limit threshold for a very brief time, PGOOD stays asserted as the VOUT rail only droops a small amount.  In another case,  however, where the fault is a much higher current than the limit PGOOD became deasserted as the VOUT rail dropped.  I have never taken the device to destructive state and monitored PGOOD and have no information on this scenario.  I will ask designers if any precautions to avoid failure propagtion have been used.

    Thanks

    Christian

  • +1 in reply to Christian Yots
    TI__Genius 14540 points

    Hi again,

    Here is the feedback from the designer.

    "We do not have any failure mode analyses done to check if PGOOD is immune to other failures in the device.

     As I understand, if a failure causes an internal short, it can compromise the internal voltage reference or ground affecting the response of PGOOD."

    With this I believe the recommendation to avoid to use the protection of an IC to protect it against failure of the same IC is a good one.

    Thanks

    Christian

  • 0 in reply to Christian Yots
    Prodigy 30 points

    thanks for the feedback

    Best regards

    Jean-Irénée Hullo