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TPS62175 Short power cycle issue

rmiller
Prodigy 90 points
Other Parts Discussed in Thread: TPS62175

I am having an issue with the TPS62175 on a new board. When I disconnect Vin and re-apply it within some short amount of time, the switcher fries. I've tried to debug the problem but it is difficult to measure since everything works fine up until the issue occurs, at which the part pops and dies. The only thing I've been able to verify is that the output rail exceeds the absolute max rating during the short-cycle event, but I can't determine if this is a symptom or just a consequence of the switcher shorting and frying.

Design details (I followed Webench recommendations):

Input rail: 24V, input capacitance 2.2 uF + 1 uF

Output: 6.0V (also tried dialing down to 5.75V), 22uF

Inductor is a 10uH.

In case it helps, it looks like the switcher always pops near pin 2 (VIN). 

Any thoughts? 

Thanks,

Rick

  • 0
    TI__Guru**** 151520 points

    With such a high input voltage and small input capacitance, the input voltage is likely exceeding the abs max ratings.  Since it seems to be repeatable, it should be easy to look at Vin with a scope when you re-apply Vin and it dies.  

    To overcome this, you need to dampen the input supply with a shorter cable or some bulk capacitance with ESR as we do on the EVM.

  • 0 in reply to Chris Glaser
    Prodigy 90 points

    Thanks for the tip. Sure enough, I added some additional input capacitance and reduced the power lead inductance and the problem went away.