Helpful ReplyHot!PIC32MZ / EC startup problems

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pic32mz_user_lw
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2015/09/07 02:39:34 (permalink)
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PIC32MZ / EC startup problems

Hi all,
 
with a new batch of our boards, which use a PIC32MZ2048ECG100-I/PF (Rev. A5), we experience start up problems. The uP does not start sporadically when powered up. The strange thing is, that, if it the uP is in this "stalled" state, it cannot be waked up / reset even by pulling the MCLR (external reset) pin low. Also the ICD3 debug tool does not recognize the uP, also it is not able to reset it.

The only thing which can wake up the uP is temporarily removing the power. Obviously the power seems to be the problem / key to the problem. When switching off the power quite a short time (100 to 200 ms) the uP can be brought into the stalled state as well as it can be started up normally (stalled - working - stalled - working ...).

We checked also the following things:
  • VDD = 2.5 V is stable in stalled state
  • VDD USB = 3.3V is stable in stalled state
  • VDD is ramping up at power on from 0 V to 2.5 within about 1 ms nearly linear, no drops in between.
  • Clock is provided by an external oscillator, signal is ok ins stalled state

Additional information:
  • USB is used (with VUSB = 3.3 V).
  • The MCLR pin is connected as shown in fig. 2-2 of the PIC32MZ data sheet.
  • Some months ago we produced the same boards with a prior batch of the PIC32MZ (but also Rev. A5), and we did not see the behaviour with these boards (which we did not really check until now, but at least it seems that it occurred much less frequently, thus we have not realized it).

When reading the data sheet I noticed, that there is a requirement for ramping up the VDD voltage:

In table 37-4 (DS60001191D-page 567):
DC17 SVDD = VDD rise rate = 0.00004 V/us to 0.0004 V/us

This means that VDD should rise within a range of 6.2 ms to 62 ms from 0 to 2.5 V. This seems to be a quite restrictive requirement concerning a wide varity of power supplies.

Interestingly the new PIC32MZ EF Family has a much wider range for this specification:

In table 37-4 (DS60001320B-page 611):
DC17 SVDD = VDD rise rate = 0.000011 V/us to 1.1 V/us
 
(This would result in a power up time from about 227 ms to 2.27 us at VDD = 2.5 V)

This looks like that the power up behaviour of the PIC32MZ EC family is at least unfavourable, thus it has been fixed within the EF family.

Is there a known issue concerning the startup behaviour?
Are there other requirements for the startup e.g. concerning the USB power?
Any hints, what we can do?

Best regards

LW



#1
danthony
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Re: PIC32MZ / EC startup problems 2015/09/09 02:00:45 (permalink)
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I have experienced this too.
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Paul Bjork
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Re: PIC32MZ / EC startup problems 2015/09/09 07:07:53 (permalink)
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Simple questions:  Do you have a different power supply on the AVDD pin?  Have you checked that that one is also stable?  I traced some very flaky behavior back to the other fluctuating supply- that I didn't even think would be an issue.  Are all of your VDD pins soldered well?
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pic32mz_user_lw
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Re: PIC32MZ / EC startup problems 2015/09/09 07:33:39 (permalink)
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Do you have a different power supply on the AVDD pin?
No - same voltage used for AVDD.
 
Are all of your VDD pins soldered well?
Hopefully yes. Soldering looks good. Also the fact, that a lot of boards are concerned, does not point to that reason.
 
Regards
 
LW
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tonykara
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Re: PIC32MZ / EC startup problems 2018/10/03 12:56:32 (permalink)
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I'm seeing this same problem now after several field reports in 2018. Did you ever find an answer?
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pic32mz_user_lw
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Re: PIC32MZ / EC startup problems 2018/10/04 00:14:46 (permalink) ☄ Helpfulby tonykara 2018/10/10 11:19:17
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We did not find a solution for the EC type. Our solution was to use the EF family and we have not seen the problem with this family. The EC family has a huge lot of bugs, thus using the EF family is a good recommendation.
 
Best Regards
LW
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tonykara
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Re: PIC32MZ / EC startup problems 2018/10/10 11:20:31 (permalink)
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Thanks for posting. I'm still looking into this. We already have a lot of EC parts in the field, and it seems to have only recently started happening for us. (At least the field reports have been recent, not sure how long the problem has really been there.)
#7
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