PIC Micro @7.7V didn't died

[ElectricGuy]

Hi;

Just to share with you guys something that i came across today.

I received a faulty board from one of my clients. It has been installed and up and running for years. It uses a PIC16F628A. Among other things it has a HeartBeat Led and Uart communications.
Everything seems to work fine, only the uart was outputting garbage.
After checking the power supply directly to the power pins of the micro, i was measuring 7.7V. It was the 7805 regulator damaged.
I replaced the 7805 and the Uart start to work again. Of course i changed the Micro too do to over stress, but is remarkable, since the maximum absolute voltage is 5.5V according to datasheet.

Has anyone come across of a something like this?

[uncle_bob]

Hi

There is a *lot* of process variation in terms of absolute upper end voltage. I have seen chips with 5.5V ratings that do indeed blow up at 6V. Most 5.5 V rated stuff will make it to >6.5V in real life.

Bob

[eugenenine]

Back when they still had a window in the top to UV erase I hooked up one backwards and it emitted light.  Switched the power around the right way and it worked fine.

[poot36]

I once hooked up a UV EPROM backwards to a homemade arduino based EPROM reader (I tried to get writing to work but didn't) and the bond wire started glowing!  I may have also have hit it (and my shift registers) with the 12V programming voltage and it did survive (not so sure about the shift registers though).  The EPROM was from a ECG or EEG machine so it should have been medical quality I would think.

[Gyro]

We had an old Prolog briefcase prom programmer (2708/2716 days) that did that if you were careless with orientation. Glowing bond wires is a pretty quick indication!