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Hot!dsPIC33FJ12MC201 Chip failure after 8 years

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Kau_Chip
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2019/05/15 01:40:19 (permalink)
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dsPIC33FJ12MC201 Chip failure after 8 years

Hi!
We have been using PIC18's and dsPIC33 parts in our products for over 10-15 years now.
Recently came across this issue in one of our old product.
We had built and tested this product in 2012 using dsPIC33FJ12MC201 and it was lying in our store room since then.
We recently received an order for this product(QEI based counter and display), so I was testing them last week.

Out of the 10 products, only 1 was working as expected. Other 9 have failed completely - show no activity.
We are using internal FRC+PLL. The code does not seem to startup and it looks like a clock failure.

Also, I was unable to re-program these chips and they show verification errors.
I have tried programming with MPLAB+PICKit3 and also with CCS Load+ ICD-U64 -> same result.
We are using the same original .hex file from 2012, also I am quite sure about
our PGD/PGC connections.

Out of the 9 devices which failed, I was able to reprogram only 1 chip.
For this chip, if I set the Fuse from FRC_PLL to just FRC, and then the code executed, albeit at a slower rate.
This confirmed my suspicion about the clock failure.

I was wondering if anyone else has encountered such an issue or is this expected behaviour?
Does the chip fail if not used for like 8 years?
We were planning to order more of these devices as we are expecting a much larger order
for this product in near future.
Any thought on this would be much appreciated!

Thanks!

Kaushik
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Nikolay_Po
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Re: dsPIC33FJ12MC201 Chip failure after 8 years 2019/05/15 06:48:39 (permalink)
5 (2)
Why you're blaming the microcontroller first? What capacitor have you choose for VDDCORE pin? May be it is electrolytic and all capacitors except one are dried and loose theirs capacitances?
There are quite demanding requirements for VDDCORE decoupling capacitor. Look for DS70265B page 237, TABLE 23-13: "INTERNAL VOLTAGE REGULATOR SPECIFICATIONS". Can you confirm your components satisfy the requirements of this table and the requirements of paragraph 20.2 "On-Chip Voltage Regulator"?
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du00000001
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Re: dsPIC33FJ12MC201 Chip failure after 8 years 2019/05/15 10:31:21 (permalink)
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Look for the capacitors!
While electrolytic caps tend to dry out (depending on storage conditions), MLCCs experience a significant loss of capacitance over time - whether powered or not.
But it might as well be some short in an MLCC: provided one developed a crack during production or from handling, further assuming somewhat humid storage, these are prone to developing shorts.
post edited by du00000001 - 2019/05/17 09:21:43

PEBKAC / EBKAC / POBCAK / PICNIC (eventually see en.wikipedia.org)
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Kau_Chip
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Re: dsPIC33FJ12MC201 Chip failure after 8 years 2019/05/17 01:42:39 (permalink)
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Thanks for your inputs Nikolay and du01 !
I will replace the caps and check these boards again.
We are using 10uF tantalum caps on all our boards and whatever products we shipped out
during 2011-2012 have not had a problem. 
 
I am suspecting the chip because we have another PIC18 part on these boards which uses the same 10uF tantalum
cap and this is working fine. The PIC18 works as master (18F87J50) handling keyboard and display, while
the dsPIC does the QEI.
Also, on couple of dsPIC chips, only the PLL seems to have failed which does not make sense
so something may have gone kaput inside I feel.
 
Thanks!
Kaushik
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du00000001
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Re: dsPIC33FJ12MC201 Chip failure after 8 years 2019/05/17 02:29:06 (permalink)
4 (1)
Not sure about the aging of Ta caps.
But: the ESR of the CAP could be critical.
 
AND I'd expect the dsPIC's PLL to be one of the first peripheral components to quit operation if the supply voltage is not pristine. (Somewhat to be followed by the ADC.)
PLLs are to be considered as analog units (the VCO is absolutely critical) and thus quite susceptible to voltage variations!!!
Basically I do not expect the microcontrollers to age other than - after extended times - "loosing" the program (from the flash). And program "loss" depends on the quality of the initial programming, storage/operating conditions. In your case, I'd search the error everywhere exempt the dsPIC  Smile

PEBKAC / EBKAC / POBCAK / PICNIC (eventually see en.wikipedia.org)
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Nikolay_Po
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Re: dsPIC33FJ12MC201 Chip failure after 8 years 2019/05/17 09:20:09 (permalink)
4 (1)
Kaushik, please report if the capacitor replacing return the chips to operation.
I'm plus one to du00000001. The PLL is most sensitive circuit inside the chip and it is directly supplied from Vdd core. Some chips, SAM4S of former Atmel, for example, have dedicated PLL supply decoupling pin and requiring the precautions to keep that pin noise-free.
Low power regulators are rather slow, the corner frequency of their gain are in range of kHz - tens of kHz. But the load is very sharp. The transition from FRC to PLL produces very sharp increase of power consumption. And some time the capacitor on Vddcore should keep the load current increase solely. It it has too large ESR, the voltage drop may lead to a failure. Even brown-out detector wouldn't help because voltage drop is not at Vdd pin the brown out circuit is monitoring.
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Kau_Chip
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Re: dsPIC33FJ12MC201 Chip failure after 8 years 2019/05/21 02:11:52 (permalink)
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Thanks again for your inputs Nikolay and du00000001!
I have not had a chance to check this, but will give it a try next week.
We have ordered new parts (dsPIC's and caps) which should arrive by end of this week.
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Kau_Chip
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Re: dsPIC33FJ12MC201 Chip failure after 8 years 2019/05/29 02:20:13 (permalink)
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I did have some new ceramic caps in smd type which I installed
in place of the Tantalum caps, but I did not see any improvement.
 
I did this change from 4 chips and they still failed to program, the chip was not being detected by the programmer.
 
 
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T Yorky
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Re: dsPIC33FJ12MC201 Chip failure after 8 years 2019/05/30 04:14:22 (permalink)
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Saw your posting and the good answers above.
Have used this chip in designs. Old product. Basic peripherals compared to later chips. There is almost a direct EP replacement.
Sorry don't mean this as any insult but you do not appear to be familiar with the chip or the code.
May I suggest using a process of elimination. Although your old design will have circuits attached to pins, start by setting up a new basic C program that does not change any config. FRC operation. No I/O. And simply counts an integer in memory, MyCount++;
Use the debugger to stop and check it is counting up/rolling over.
Do this under the develop environment you normally use.
This will work. If not you have a basic board problem. And go from there.
The advice is to consider the development tools of 'the day'. Use a picket3 that was available at the time. I have found that the older chips are not supported as well as the newer chips, on the new tools (s/w and h/w).
After progressing with working 'new' test programs, it will steer you towards the issue.
Think about re-constituting the environment of 'the day' when the development was done.
Do not presume your Pickit has the correct firmware. ALWAYS manually download the firmware of the development environment you are using.
Trust this assists.
T Yorky.
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