Misconnected Pickit3 - dead MCU - Page 1
Forum section: electronics / general

author: miceuz
author_rank: Frequent Contributor
timestamp: January 20, 2015, 08:56:29 pm
content: Yesterday was a sad day.I have unfortunately misconnected Pickit3 to the PIC18F4620 board I'm working with. I'm not sure exactly, but I think I have shifted Pickit3 "left" so that MCLR pin went into VDD pin, etc. The board was energized during the event. After the event the microcontroller instantly went dead - no stuff displayed on LCD, no led blinking, no nothing. I can connect to the chip via pickit and query it's ID, but can't programm it anymore. Even more, the relay that's connected to PB5/PGM pin is buzzing when I try to programm (I don't use LVP).Nevertheless it's strange - MCLR/Vpp shouldn't be high voltage when not programming, should it?

author: neslekkim
author_rank: Super Contributor
timestamp: January 20, 2015, 09:00:10 pm
content: strange, I have connected my pickit3 upside down without hurting the chip, maybe i was lucky?

author: Howardlong
author_rank: Super Contributor
timestamp: January 20, 2015, 09:11:38 pm
content: Quote from: miceuz on January 20, 2015, 08:56:29 pmBy "high voltage" what do you mean? Is it at Vpp or Vdd or something else?

author: miceuz
author_rank: Frequent Contributor
timestamp: January 20, 2015, 09:19:22 pm
content: Quote from: Howardlong on January 20, 2015, 09:11:38 pmVpp is up to 14V according to microchip documentation.

author: Andy Watson
author_rank: Super Contributor
timestamp: January 20, 2015, 09:30:24 pm
content: I would have thought it more significant that programmer VDD would have been connected to the target's ground causing the programmer's ground to drive the target PDG pin negative.

author: Howardlong
author_rank: Super Contributor
timestamp: January 21, 2015, 05:12:02 am
content: Quote from: miceuz on January 20, 2015, 09:19:22 pmSorry, I assumed you were telling us that you were experiencing that the MCLR pin was at an unexpectedly high level.No, MCLR/Vpp should usually be at or aound Vdd, or, of course, Vss temporarily during reset.

author: miceuz
author_rank: Frequent Contributor
timestamp: January 21, 2015, 02:06:00 pm
content: Just replaced the dead microcontroller, so yeah, lesson learned - you *can* fry MCU by shifting your Pickit in the connector.

author: mazurov
author_rank: Frequent Contributor
timestamp: January 22, 2015, 05:31:45 am
content: That's why I'm using ICD - it has keyed connector. You only need to pay attention once while soldering "5 pin to RJ-11" adapter to the MCU board.

author: voja
author_rank: Contributor
timestamp: January 22, 2015, 08:50:15 am
content: That's why I removed the original female connector on Pickit3 an placed tne Nylon 2.54 mm 5-pin male connector instead (ignoring pin 6). I only had to cut the part of nylon as it was too thick to place the Pickit cover. Now I can use crimped female connectors on my programming cable, with low possibility of frying MCUs. Pickit opening was also the good moment to remove the buggy S1 key (upper right on the photo), which kills some MCUs.Another thing to note is that Pickit or ICD or target system can be fryed if you connect/disconnect the programming connector, even if the target system is not energized (but only connected somewhere else), as there might be high potential voltage differece between the GND contacts. So if the signal contact is established before GND, there will be the high voltage spike at some input. So I have GND on my laboratory DC supply shorted to my computer's GND. I was lazy to do it before, so I fried two ICD2s a few years ago.

author: 22swg
author_rank: Frequent Contributor
timestamp: January 22, 2015, 10:07:28 am
content: Voja Thanks for that , been using PK3 some time always been careful about pins and GND , after I killed a PK2

author: Howardlong
author_rank: Super Contributor
timestamp: January 22, 2015, 04:16:16 pm
content: Although I am not doubting that it may be possible to blow up a PIC by mis-connecting the ICSP, I'd say you have to be unlucky, I'm always wiring them up wrong, even after I think I've double checked it. I don't know why, must be a form of wiring dyslexia!I can't ever remmeber breaking a chip though despite my errors.

author: dannyf
author_rank: Super Contributor
timestamp: January 22, 2015, 04:18:46 pm
content: QuoteIt generally happens if the programmer is powered on after the board is powered on.In those cases, you can burn the OS onto the pickit to bring it back to life.

author: voja
author_rank: Contributor
timestamp: January 22, 2015, 04:57:07 pm
content: I never had the bad experience switching Pickit supply (via USB) and target board supply on and off, at any order, but I learned not to (dis)connect programming cable if GNDs (at Pickit and target board) are not at the common voltage level

author: Skimask
author_rank: Super Contributor
timestamp: January 23, 2015, 04:14:14 am
content: Quote from: Howardlong on January 22, 2015, 04:16:16 pmSame here. Vpp on Vdd, Vdd swapped with Vss, 5v on a 3v PIC, the list goes on and on.The only time I've wiped out PIC's is when I've zapped them with visible/audible static shocks.Even then, most of those might end up with a single blown pin, which may only have needed an external pullup to replace the blown internal high side FET, or maybe that particular pin may have been blown out completely.Point being, at most maybe a couple totally dead since I started messing with PICs back in '90.

author: Berni
author_rank: Super Contributor
timestamp: February 14, 2015, 09:48:15 am
content: I have plugged in a Pickit 2 and 3 backwards or shifted lots of times and all i got was a error message about a wrong device ID.I did menage to partially blow up a Pickit 2 when i had a board with -12V on it and a accidental short sent the -12V in to the digital supply rail. That Pickit 2 now refuses to supply power to the board but, but when given external power it still flashes PICs just fine. O0Seams to me like you really have to try hard to completely fry a PickitAs for sending 5V in to 3.3V PICs they seam to survive that too. I heard stories of PICs being put in sockets backwards (Especially nice on the 18 pin ones as Vdd and Vss swap), getting hot enough to burn your finger and after being put in the right way around still working.