what problems are happen in TPS51916?

Shinya Muramatsu

Other Parts Discussed in Thread: TPS51916

TPS51916 abnormal waveform.xlsx

My customer have some trouble about TPS51916 on their circuit.
VDDQ output is abnormal,(normal:1.1V→abnormal:2.08V)
We check this behavior because IC are already broken.
in this case, IC(supply5V)is hot when S3 and S5 are high.(Please see attached file)
I think over current for short IC.

I guess discharge FET is broken at discharge operation.
Is constant current operation at the time of the discharge ? or not?

I checked ,but I could't find Strange point in thier circuit.
except 44uF capacitor is near VTT-pin.
 
and Could you give me other advice about this problem?

If you nedd their circuit information,Please change to private session.

over 9 years ago

0 JohnTucker over 9 years ago

TI__Guru**** 191445 points

is this only one circuit that is bad? does it work properly if you replace the device?

0 Shinya Muramatsu over 9 years ago in reply to JohnTucker

Expert 1010 points

thanks for advice,Mr Tucker.
not only one. TPS51916 were broken on 3 boards of 10 boards.
but all boards operate normaly at first.
We think board design or use case is over absolute spec.
Could you give me other advice

0 JohnTucker over 9 years ago in reply to Shinya Muramatsu

TI__Guru**** 191445 points

Violating abs max specifications will most likely cause ICs to fail. Maybe noise or overshoot on the switch node is causing EOS on the discharge FET. Can you submit one of the damaged parts for failure analysis?

0 Shinya Muramatsu over 9 years ago in reply to JohnTucker

Expert 1010 points

Thanks for answering,Mr.Tucker.

I think failure analysis is expensive,first I want to check discharge FET spec.

Is constant current operation at the time of the discharge ? or not?

And Could you advice me other reason?

0 JohnTucker over 9 years ago in reply to Shinya Muramatsu

TI__Guru**** 191445 points

It looks like the discharge currents are constant current except when operating in tracking mode. in that case the current is adjusted so the outputs track each other during discharge.

0 JohnTucker over 9 years ago in reply to JohnTucker

TI__Guru**** 191445 points

Is it possible you have a pre-bias voltage on VDDQ? Does your circuit operate normally if the load is completely removed (open circuit)?

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what problems are happen in TPS51916?