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TPS2549-Q1: TPS2549-Q1 Short to ground / pin 13 (FAULT) = 0V - 100ohms

Klinger Lima
Prodigy 20 points
Part Number: TPS2549-Q1
Other Parts Discussed in Thread: TPS2549

Hello everyone,

I have four Radios' PCBs that the USB bus is working on (when connecting a USB stick it detects the device and plays an audio). However, a "ground to short" is being identified in my test station. The voltage reading on pin 13 of these suspect PCBs is at 0 V and the ground impedance is below 100 ohms. Comparing to a good pcb, the voltage read on pin 13 (Fault) is 3.3V and the impedance to ground is close to 16kohms. What can I do to identify what the problem is, what caused this failure?

  • 0
    TI__Expert 8420 points

    Hello ,

    Thanks for your question, we will reply you soon.

  • 0
    TI__Expert 8420 points

    Hi Lima,

    Could you help to clarify the  "Ground to Short"  The TPS2549 don't support this short protection and Fault assert.

    Your question is Fault pin in some case assert to set low and  some case not assert but keep high ?

  • 0 in reply to Michael Tan
    Prodigy 20 points

    Hello,

    Let me try clarifying for you, my test station (EOL) detect a failure mode (USB short to ground). When analyzing a bad part and compare with a good part the pin 13 (FAULT) is 0V and the impedance to ground is around 100 ohm and all good parts have 3,3V in pin 13 (FAULT) and the impedance to ground is around 16kohm. The curious thing is that it seems that the USB bus is OK, because the radio recognizes a pendrive and plays normal music.

    My question is "what does this behavior mean on pin 13?" pin 13 (FAULT) is 0V and the impedance to ground is around 100 ohm

  • 0 in reply to Klinger Lima
    TI__Expert 8420 points

    Hi Lima,

    The FAULT pin internal is a open drain FET , when the fault behavior is happen the FET be turn on and FAULT pin will connect to ground through this FET.

    So you see a low resistance between FAULT to GND. 

    You mention the failure mode is 5V OUT pin short to ground .If the OUT short to ground it should touch the Iout current limit  and FAULT will set low.