Anybody else using the FRAM 25256 memory?

[rmozer]

We have a solar powered 16F6722 based product that uses the FRAM 25256 memory. We are very happy with it when it works but we have a significant number of failures (2-3%) that has me concerned. Memory that initially worked fine for months seems to fail for no apparent reason. The typical failure leaves the memory unwritable and showing patterns of FF 00 through out the entire memory range when read.

Does anybody else have experience with this memory?

And of course the loaded question, Any ideas?

[PCM programmer]

There are several erratas on this chip and related versions of it.

This one is about the order in which the commands are sent.
http://www.ramtron.com/lib/literature/datasheets/Errata004_25x256.pdf
Are you doing any of those command sequences ?

Here's the archived erratas page:
http://ramtron.com/doc/Products/archived.asp

You should look at all the 25x256 errata and see if they apply to your problem.

[rmozer]

Thanks for the suggestions but I have read the errata and data sheets and believe that we are interfaced correctly and are using good code to work the memory. With about 1000 units installed the problem is showing up on only a small percentage of the sites and usually after several months of service.

I have sent an e-mail to Ramtron and will follow up with a call to them when I return home from the field.