We are having some production issues with a small number of our boards at low temperatures. The DA14531 seems to reset erratically and constantly, then work acceptably after it warms up. We have been in production for over a year now and not made any changes to the firmware or hardware since then. We are powering the board with CR2032 batteries that are brand new.
We have two primary causes suspected.
1. Temperature issues with the crystal. Any advice here? Has Renesas / Dialog seen this issue with other customers and crystals?
2. A capacitor issue with C3, the 10uF capacitor for buck mode operation. We have seen that in defective samples, replacing the 10uF capacitor with a 1uF capacitor fixes the issue. Is a 1uF capacitor acceptable? What will be the effects of this change?
Any other advice or thoughts would be appreciated.
Thanks for your question online. Let us check this internally and will get back to you.
In the meantime, can you kindly raise a ticket via the "Submit a ticket" form and provide more information about your product? It's 1-1 support so please feel free to share more info.
Right hand-side column on this webpage: https://en-support.renesas.com/dashboard
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Question : also mentioned "low temperatures", so in which temperatures are you testing it ?
PS : when submitting the ticket, in the Inquiry "Product Category pull-down, select Wireless Connectivity and set all the other filed accordingly.
I performed some more testing. Swapping a defective unit's 10uF capacitor with 1uF did not help. Swapping the defective units bad crystal with a known-good crystal did not help. Swapping the DA14531 between a bad board and known good board made the bad board work, and the good board fail.
So, we are wondering if we are having some issue with the DA14531 at low temperatures.
I will open a support ticket.
Thanks for raising your question on our private ticketed system. Will follow up there.