We have a design that uses the xmega256a3u and a 32.768 kHz external oscillator. What we have noticed is that on about 10% of the chips if you use the RTC divide by 32 to reduce the oscillator to 1 kHz, and then run at low temperature the RTC is very unstable. However, if you do not divide by 32 then the RTC is very stable at low temperature.
We are not running the oscillator in low power mode, that just makes things worse.
Anyone observed anything similar?
Still doing testing to try and see if it is just the RTC or if there is some instability in the crystal. Initial testing shows the the system clock running at 32 MHz is very stable using the external oscillator as calibration.