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LM63635-Q1: Vcc Pin short to GND cause IC damage

Hsu chien chih (Jay)
Prodigy 10 points
Part Number: LM63635-Q1

Hi Team


1.According to "Functional Safety FIT Rate, FMD, and Pin FMA" Tabel4.2, the description of Pin 4(Vcc) short to GND is Fault mode will shut device off, but I set Up Vin 25V,output 5V, then short to Vcc Pin to GND, the IC damadge (sparks and smoke ), not match Tabel4.2 description.

2. The internal regaulator output protect is? (limit spec)

3.Vin 25V, then Vcc short to GND, the failure step is following below?
--> internal regaulator fail--> Low side MOSFET fail --> High side MOSFET fail --> continue supply power--> high energy at IC --> Over SPEC --> IC sparks and smoke ?

*The Power supply 25V,limit current: 12A

  • 0
    TI__Genius 13735 points

    hi,Jay,

    Could you try another test and limit the power current like 100mA  to see whether the device not damage ,then we could confirm the cause is as your said. the Pin FMA table result is a simulation result .

    Elena.

  • 0 in reply to Elena Gao
    Prodigy 10 points

    Hi Elena:

    I try input 25V 100mA, measure Vout is 5V, then short Vcc to GND(use a push button) about 1sec. and release. The IC not damage, but IC  Vout not recovery, and I power off about 2~3Sec. and return on 25V,100mA, that IC Vout normally.

    1. I want to know that input condition of " Pin FMA table result is a simulation result" .

    2. Why Iimit current 100mA, that IC not damage?

  • +1 in reply to Hsu chien chih (Jay)
    TI__Genius 13735 points

    hi Jay,

    All the short test should be limited the current, to prevent the current ramp higher when short status. The reason you mention NO3 should be right if the current is not clamped.

    Elena