• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 98 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.

TPS4811-Q1: Short circuit protection caused device failure

Alex Everest
Prodigy 10 points
Part Number: TPS4811-Q1
Other Parts Discussed in Thread: TPS4810-Q1

Tool/software:

I am having trouble using the TPS4811. The end goal is to drive an inductive load, but on the bench I found that during a short circuit test, the TPS4811 let out the magic smoke!
Previous to failing, I was switching in 6A of resistive load without any problems.

The device setting components (calculated using the supplied design spreadsheet) should translate to 70A overcurrent protection and 100A short circuit. The loads required can pull up to 50A, but are only ever used for a few seconds at a time.
12V normal input, but components should allow it to work down to 7V.
I have found that the R4/R5 divider resistors have blown up as well.
Any ideas about why the short circuit caused the components to fail instead of tripping would be great.

  • 0
    TI__Mastermind 34905 points

    Alex,

    My suspicion on what might be happening here is that when the short-to-ground event happens, the supply voltage is likely swinging negative. If it goes below the full -1V that we spec as the minimum in the datasheet, the ESD diode would potentially bias (without an ESD event) and there could be the potential for "magic smoke". 

    A good way to prevent this would be to put a diode on the the ground pin with the anode facing the GND pin of the TPS4811-Q1. This would make it so that in any sort of transient event (such as short-to-ground), the ground pin would be isolated from said voltage, the ESD diode wouldn't BIAS, and there would be no smoke.

    Do you have a waveform of the STG event? VS, EN, VOUT, and current (if possible) would be helpful here.

    Best Regards,
    Tim 

  • 0 in reply to Timothy Logan
    Prodigy 10 points

    Hi Tim,

    Thanks for the advice, I will re-design and have a go with the added protection diode.
    Sadly I didnn't capture a waveform of the event, but I will make sure I capture the data next time.

    Out of interest, do you have a theory about why this might have also caused the resistors R4 and R5 to blow?

    Thanks

    Alex

  • 0 in reply to Alex Everest
    TI__Mastermind 34905 points

    Alex,

    What I am guessing happened is that when the voltage spike happened, the ESD diodes biased. The ESD diodes are meant for ESD events (nanosecond) level and when subjected to DC they failed short.... which likely cause an internal short from VBB->EN->GND and cause a lot of power to be dropped over resistors that are not rated for said power. TPS4810-Q1 would be a bit more resilient here for negative voltages. 

    Best Regards,
    Tim