Author Topic: Mysterious Catastrophic Failure of PICs ??  (Read 1765 times)

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Offline Icarus

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Mysterious Catastrophic Failure of PICs ??
« on: December 03, 2013, 07:17:49 pm »
Hi everyone;
I'm trying to make BLDC motor driver for my toy quad copter project.
For the microcontroller aspect it is no different from blinking Leds. I soldered the PIC and it was working.
So, when I have begun to test h-bridges (with NO LOAD) ,the PIC became a shortcircuit.
I tested regulator immediately (LD1117) and it was just fine. PCB is okay and no wrong footprints.

I'm very surprised I've no idea what happened.
Is there any counterfeit pics ??
 

Offline Svuppe

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Re: Mysterious Catastrophic Failure of PICs ??
« Reply #1 on: December 03, 2013, 09:12:21 pm »
I don't know about the PIC, but there is an obvious fault in your gate driver.
When Q5 turns on, the E-B diode of Q4 will make a big fat short from 12V to Q5 and ground. Maybe Q5 fails in a way so you're getting overvoltage fed backwards into the PIC?
 

Online free_electron

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Re: Mysterious Catastrophic Failure of PICs ??
« Reply #2 on: December 03, 2013, 09:14:14 pm »
back emf and virtground can be higher than vcc of the pic... that may cause latchup
Professional Electron Wrangler.
Any comments, or points of view expressed, are my own and not endorsed , induced or compensated by my employer(s).
 

Offline Icarus

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Re: Mysterious Catastrophic Failure of PICs ??
« Reply #3 on: December 03, 2013, 09:33:54 pm »
Ouch ! I completely missed those.
Thank you so much guys.
 


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