[SI-LIST] Re: CPLD getting blown on board

  • From: Danny Damhave <dd@xxxxxxxxxxx>
  • To: cygnul@xxxxxxxxx
  • Date: Fri, 7 Jun 2013 16:05:04 +0200

Hi Sam,
Powerup is one thing but don't forget to check the power down of your circuit, 
many people forget this case.
a) Power down sequencing of your CPLD
b) Power down of others ICs/Pullups driving the CPLD I/Os compared with the 
CPLD IO Supply
c) Power down (and powerup) of any external equipment interfacing more or less 
directly with our CPLD
Also consider if RESET disables some of your power supplies (eg the CPLD IO 
supply) or make them exceed their max specs due to load changes at reset.
Best regards
Danny Damhave
PS You can also consider to contact one of the companies specialized in 
external design reviews. in Denmark e.g. we have Devir ApS (www.devir.dk)




On 07/06/2013, at 14.38, Sam Pete wrote:

> Hi Friends,
> I am working on a medical board which has multi-core CPU along with other 
> peripherals.
> we are getting into some issue that CPLD is getting blown out during power 
> cycle or sometimes during reset.
> out of 210 boards we produced, we have 3 boards exhibiting this issue. The FA 
> report from CPLD vendor says electrical over-stress...
> The board is not having any hotswap peripherals.... CPLD has 2.5V and 3.3V 
> banks, 3.3V Core/IO supply comes up first then 2.5V.
> We have gone thru all sorts of checks, negative tests etc., to reproduce this 
> issue and we were unsuccessful.... 
> Does anybody faced similar issues earlier? Appreciate if you can provide some 
> clues...
> 
> thanks
> Sam
> 
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