DS90UB954-Q1: lock loss at cold temp

Hi David, 

Thanks for your question. 

What temperature is it losing lock at, 0C or -40C, etc? Is the SER, DES, or both subject to the low temp? 

Also, do you have probing access to voltage rails, strap pins, etc during low temp testing (sometimes accessible with Thermo-streams, but not usually with chambers)?

Initial ideas that come to mind could be the power rails might not be stable across full temp range, and low temp causing instability and lock issues. I wouldn't expect enough temp variance in the strapping resistors to cause issues. It might also be good to check the type of bypass capacitors used, and if they are choosing the correct temp class based on their requirements (X7R vs. Y5V for example). 

Regards, 

Logan

Hi Logan;

We have tested with both SER and the DES in the chamber, and with only the SER in the chamber.  We don't see any difference.

Hi David,

If I'm understanding correctly, the problem is observed also when only the SER is in the chamber? This likely indicates that the issues are on 953 side instead of 954. 

I'll review the additional design files you sent, and get back to by tomorrow. 

Logan