Hi
We have for several years manufactured two variants of the same product, one with a RTC backup battery installed and one without (the PCBs are identical).
The product has a specific known error, which we have struggled to identify - as explained in detail in this thread. In short, the MCU (TM4C1233H6PM) becomes non-responsive.
We now have statistical significant data showing a higher failure rate specifically on the variant with the battery installed (we previously suspected the supply circuit to be the problem).
The battery is used to drive the TIVA hibernation RTC clock - such that the time is retained when power is disconnected (we do not use any other features of the hibernation module). The problem occurs even if we do not enable the hibernation module in SW (only install the battery).
The hibernation/RTC/battery circuit is given here (PE is ground). The battery is a 3V coin cell of type CR1225.
The circuit is based on suggestions from this thread. One difference is the value of R_HIB_2, which is selected to keep the unique component count low.
In short, it we install a battery in above circuit, we see a higher failure rate, even if the hibernation module is not enabled in SW.
Any suggestions on why this happen will be highly appreciated.
Thanks
br
Christian