STM32G0B0RET6 failure rate

[Zdiode]

We are on the second generation of prototype here.

On the first generation I had an MCU fail for reasons I couldn't trace.  This was from a set of six.

I have now powered seven of the second generation two have had MCU failures.  The second failure was on the prototype's initial turn on.  No code had been loaded into it.  A hole blew out of the part when power was applied.

All failed parts then shunted the VCC to ground with a low impedance, less than 100 ohms.

I have included part of our schematic.  Do you see anything that could explain this failure?

Best regards,

Bill Grimm - Zdiode

[TDK]

> The second failure was on the prototype's initial turn on.  No code had been loaded into it.  A hole blew out of the part when power was applied.

Definitely suggests overvoltage on a pin.

Schematic looks okay.

I would guess one of the signals coming in exceeds the allowable voltage, possibly due to a spike on startup.

If parts are still responsive, you may be able to determine which pin or port is blown by set each pin high (set pin as output and set GPIO->ODR) and see which one still reads low (read GPIO->IDR).

Probably this spike is happening on the other parts too but it just hasn't caused failure (yet). Putting a scope on each incoming pin and monitoring during startup may be informative.

1/6 and 2/7 are way above the expected failure rate of the chip.

[Andrew Neil]

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@TDK wrote:

Definitely suggests overvoltage on a pin.

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+1

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@TDK wrote:

I would guess one of the signals coming in exceeds the allowable voltage, possibly due to a spike on startup..

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+1

The schematic shows that there is (at least) 24V elsewhere in the system; also lots of external connections with "motor" in the name...

And no sign of any protection or suppression on any of the external connections.

PS:

Another possible cause is applying signals to the MCU's pins when the MCU is not (properly) powered and/or grounded ...

[Uwe Bonnes]

Can you explain what you intend with the combination of Q1/D1 and Q2/D2?

Otherwise your error for me also looks like overvoltage.

[Zdiode]

Q1/D1 and Q2/D2 are reverse voltage protection.  I have wondered if one or the other is sufficient.

[Zdiode]

If I can do it I will do it.  At least this is a good technique to remember for the future.  Thank you!

None of the damaged parts so far have been in any way usable.

[Zdiode]

On the first one that failed in this set, I removed the part after it fried.  I will test the prototype with its pins open and see if I see any overvoltage.  Perhaps with the processor removed, I  will see the high voltage.

I am not in the office today due to a big snow storm.

Best regards,

Bill