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Newbie nplayle
Newbie
500 Views
Registered: ‎10-30-2018

XC9572 ESD Sensitivity

Hello, 

 

We've got a deployed design that uses an XC9572XL CPLD. Its role is essentially a glorified multiplexer / decoder. 

All the outputs from the CPLD go through other ICs before they reach the outside world, via level shifters or RS232 converters, except for 2. Those outputs go direct to the outside connector, with no ESD protection or other protection devices. These I/O are unused and undriven. 

 

So far, we have had 2 failures where the CPLD appears to short circuit - it stops working, gets hot and draws lots of current. 

 

Our only suspicion we can think of is that one of those two pins are hit with an ESD event which causes the short circuit that we are seeing. Could their be another explanation? What other failure modes exist in the CPLD? 

 

We're looking at getting an ESD gun to test this more thoroughly, but in the interim, any advice would be appreciated. 

 

Thanks,

Nick

 

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2 Replies
Scholar u4223374
Scholar
450 Views
Registered: ‎04-26-2015

Re: XC9572 ESD Sensitivity

2 failures out of how many samples? If this is really common (eg. 2/4 boards have failed) then I'd take six off the shelf, cut the tracks to those pins on three of them, and see whether you can replicate the failure. If you can only cause it on the unmodified boards, that's pretty good evidence.

 

The XC9572XL has 2000V ESD protection, which seems to be normal and should protect it pretty well.

 

Other things I can think of that might be particularly relevant to this design:

 

  • Genuine chips. For older chips like these, it's not unusual to find "bargain" priced ones on eBay or Alibaba. However, you have no idea (apart from the seller's promise) that these have been handled correctly, or even that they're genuine parts (as opposed to "retrieved from the Xilinx rubbish bin" parts). Are these from an authorized distributor? If not, that's an easy one to fix, since they're still available from Digikey (and others).
  • Voltage supply. If this design was updated from an earlier XC9572 (not XC9572XL) one, then you need to have a close look at your supply voltage. The XC9572 ran at 5V; the XC9572XL will probably run at 5V for a short while, and then fail.
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Newbie hannahxan
Newbie
292 Views
Registered: ‎10-06-2018

Re: XC9572 ESD Sensitivity

We're looking at getting an ESD gun to test this more thoroughly, but in the interim, any advice would be appreciated.  CCleaner  Happy Wheels  VLC

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