We have been using the TMS320DM368ZCED in one of our products for the past 8 years. We run an Environmental Screening Test on each unit which brings the unit down to -40C, soaks for an hour, then powers up for a quick test. Recently, we have been experiencing booting issues at temperatures ranging from -20C to -40C on 13% (8 of 60) of our production boards. At these cold temperatures, the processor fails to load the UBL from NAND and aborts.
In our debugging, we’ve replaced multiple NAND IC’s and experienced no changes (i.e. failures at the same temperature). We also verified that the power supplies function normally during failed boots and X-Rayed the parts to ensure that there were no issues with the soldering. We have only experienced a change in result when we replaced the TMS320DM368ZCED processor on a failing board. We had a board that failed to boot at -20.3C. After we replaced the processor, the same board with a new processor booted at temperatures down to -36.2C (as close to -40C as our chamber would go). We are not 100% sure that the processor is causing the failure to boot at cold, but based on the result from replacing the processor it does seem likely.
Have anyone seen issues with this processor at cold temperatures before? Are the lots are tested at the rated temperature ranges (-40C to 85C)? Or are they designed to meet?
We really appreciate any help regarding this issue. Thanks!