Mega128 subject to MAJOR overvoltage

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#1
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So I was troubleshooting for a while why my LCD display fried. It was plugged into my PCB running a Mega128. Thinking I had a bad LCD, I plugged in a new one to find...ouch! It heated up so fast the bubble chip on the back left a burn sport on my left index finger :) I did some basic troubleshooting... Mega128 is up and running, talking to terminal, reading ADC inputs, etc... Hmmm... so I put my meter on VCC to find 11 volts!!!!!! My 5VDC wal-wart failed! I quickly unplugged it and after the smoke settled, I replaced the wal-wart. The Mega128 survived 11 volts for at least 10 minutes while troubleshooting!

I'll tag this board just in case problems creep up later, but way to go to Atmel! How the thing is still working is beyond me. You figure I was WAY over the max VCC spec. I guess I cannot rely on the other devices on this board...

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An engineer I work with has done that a few times and the AVR keeps working like nothing happened. 8)

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Send me a PM and I'll tell you how to treat the burn. :D

Glad the chip works.

JC

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Cool :) Never thought it survived that :)

But it could be just a coincidence since two chips arn't alike.

But cool anyway :)

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I'd still recommend you check everything you intend to use. Just last week I had a friend working with an AT90CAN128 (almost the same as mega128 cept CAN instead of another UART) when he hooked up 12V on accident.

Needless to say he unplugged everything right away and it seemed fine for a few days. However, he started developing stuff for SPI and found that half the pins on the SPI port wouldn't drive a low but would drive high. Caused alot of headaches till he figured this out.

I'd just suggest you be skeptical until you use it all. :)