STUSB4500 IC failure in the field

[nickray]

Hi all, my team is experiencing some boards have failure of their STUSB4500 sink PD controller. We have not 100% determined the cause yet, but I found that our implementation is only using 0.1uF caps for the VREG 1V2 and VREG 2V7 decoupling. This is way under the datasheet minimum of 0.5uF.

The failure mode we are seeing is that the STUSB4500 does not communicate on USB PD at all after failure. On both failed boards I have received back, VREG 1V2 and VREG 2V7 output ~0V. 

My question: is it possible or likely that the 0.1uF decoupling caps are causing or leading to this failure? The STUSB4500 is programmed to negotiate 12V, also. So the operating condition would be to negotiate 5V on plugin, and then negotiate 12V. 

Thanks!

[NBALL]

Hello

capacitors for Vreg1v2 and vreg2v7 shall be 1uF typ.

LDOs are not designed for 100nF cap.

Best regards

Nathalie

[nickray]

Thanks Nathalie. 

Do you think this could be a regulator stability issue? And do you think that instability could cause permanent damage? On the boards we have with inoperable STUSB4500s, the damage seems permanent. Here is a rampup curve we captured on an undamaged STUSB4500 with 0.1uF regulator caps (ignore 2V5 text, its 2V7). 

Ultimately, we are curious if 0.1uF regulator caps permanently damage the IC. Thanks!

[NBALL]

It could be that regulators are out of regulation. If output of VREG2v7 overshoot or follows VDD, it will damage the component.

Best regards

Nathalie

[nickray]

So potentially, in an out-of-regulation state, do you think VREG2v7 LDO could pull enough current to fry the VDD input (bond wire)?