topic Consequences of supply voltage problems - e.g. MC68HC908JW32 in 8-bit Microcontrollers

Consequences of supply voltage problems - e.g. MC68HC908JW32

andym8 — Mon, 06 Apr 2009 02:16:40 GMT

Hi, What are likely symptoms and issues seen when a MCU, eg. MC68HC908JW32, receive large voltage spike / over voltage.

Many Thanks.

Added p/n to subject.

Message Edited by NLFSJ on 2009-04-07 10:06 AM

Re: Consequences of supply voltage problems

peg — Mon, 06 Apr 2009 17:53:35 GMT

Hello and welcome to the fora, Andy

In my experience the first abnormal behaviour that occurs with excessive noise - spikes on the power supply is unexpected transitions being recorded on i/o pins. This is especially noticable on pins that generate interrupts.

Re: Consequences of supply voltage problems

andym8 — Sat, 11 Apr 2009 00:59:04 GMT

Thanks for the insight. What about possible permanent damage?

At what sort of levels could damage be done, is it possible to 'burn the chip out' through overheating maybe?

Many Thanks for your time.

I will check when I return to work, but I believe quick basic tests had showed supply V+ was now directly connected to D+. I presume this is not desirable. MCU was still incircuit so problems could be elsewhere.

Re: Consequences of supply voltage problems

peg — Tue, 14 Apr 2009 04:26:53 GMT

Of course, exceeding the absolute max voltage specs with a solid power supply for any length of time will generally destroy the chip. Sometimes you can be lucky and it still works, but it will more than likely be prone to failure later.