Tough PIC

[Charles Linquis]

One of my circuits uses an 18LF2523. When we were bringing up the board for the first time, a technician noticed that the circuit was working, but the voltages were off. He measured VCC and found that it was 11.5V! A diode had been installed backwards.
The PIC had been working fine for 15-20 minutes before the problem was noticed. He reversed the diode and the circuit (and the PIC) worked normally.
I didn't try all the peripherals, but the USART, the PWM and all the I/O pins I tried were working normally.

Of course, we replaced the PIC before shipment for reliability reasons.

[spcw1234]

Impressive! I might try that tonight with one of my PIC's

[Ioannis]

Please put on your safety glasses, a helmet and gloves. It may blow!

Post your interesting result hen...

Ioannis

[Charles Linquis]

I have mentioned it before, but I once used 16C73 (I'm embarrassed to say that I ever used 16 - series chips). The 16C73 was one in a ceramic package and a quartz window (it was UV-erasable, remember those?). Because it had to be put into an eraser for 10 minutes every time I wanted to reprogram it, I was constantly plugging it into, and pulling it out of, a nylon 3M proto-board. After one such insertion, I smelled something and looked over at the proto-board. Smoke was rising! I shut off the power and (stupidly) used my finger to see just which component was overheating. I touched the PIC and got a blister on my finger. After the PIC had cooled down, I removed it from the protoboard, and the 'groove' under the chip was melted. The nylon was dark brown as well. I noticed that I had installed the PIC backwards.
I was sad that I had to throw the PIC away (the erasable ones cost $20 each back then), but before I did, I put it back in the protoboard in the correct orientation. It worked!!!

About the same time (also with a PIC16C73), I needed a 20Mhz crystal. I didn't have any, but I had lots of TTL 'can' oscillators. I didn't have any 20Mhz parts, but I did have a 24Mhz oscillator. I tried it. It worked - no problem. So I kept plugging in higher and higher frequency oscillators. It ran fine at 57.6Mhz, but didn't work at 64Mhz. I can't say that I tested everything at that frequency, but it did a fine job of reading the A/D and adjusting an EEPOT in a "tracking" mode.
VCC was 5V. Who knows what it would have done if I had raised the voltage to 11V!

So - you can overclock PICs.

[Darrel Taylor]

Here's an 18F2550 that was powered with 15V for ~15 minutes.



A 30F3012 was on the same board. It got hot, but didn't melt like the 2550.
Neither of the chips worked afterwards.



Keep those safety glasses on!

[Ioannis]

On the last picture, there is "melabs.com" and 30F3012 chip. Can I speculate that something you are cooking there at Melabs?

Ioannis