What is causing MC9S08GT60 failure with high current draw?

[etaychert]

This has happened twice now and with the few boards I've used, it amounts to about a 20% failure rate...

The first time was a on a DLP rf2z, (MC13191 RF & MC9S08GT60 board). It stopped working and, in looking at it it, I found 9 ohms across VDD and VSS.

On a second, in-house design, the board started browning out its regualator. After cutting the VDD pin on the MC9S08GT60, I found 16 ohms across it and ground...

No problems were found between VDDAD and VSSAD which were tied to VDD and VSS on both boards and both boards had dozens of hours of use before failure.

Have you seen anything like this?

I don't think it's ESD because there are a lot of other boards moving through here without problem, the only thing I see different from the other work and common to these two is the P&E USB multilink used for programming them... That hasn't shown any ill symptoms of its own but I'm getting worriied as my short pile MC9S08GT60 chips is only getting smaller.

Stumped,
- Ed.

[RaghuSorab]

David, I didnt get your sentence viz.. hard tied to ground. What does this mean

[peg]

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Raghu Sorab wrote:

David, I didnt get your sentence viz.. hard tied to ground. What does this mean

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Hi,

Actually I never said "to ground".

I meant that it was shorted to Vdd or Vss. Probably due to it being meant to be an input with a switch on it or something, but it got configured as an output and driven the other way.

That's all!

Regards David

[peg]

Hi Ed,

Unfortunately for you, in my experience, nearly all the time, after MCU failure you end up with a space heater (low ohms from + to -).

PCB shorts - solder shorts - accidents that short i/o to supply or other power sources configuring pins as outputs when the pin is hard tied all mostly will do this. You find and fix this but its too late for your MCU.

Regards David

[etaychert]

Thanks David.

Well I guess that I've never blown a whole chip before. A port or a pin, yes... I'd always assumed that something would "open" when it blew; now I know better!

- Ed.