RTC Drift with internal RTC & internal 32kHz oscillator - STM32H503

[prahaladh_srinath]

Hi...

We are planning to use STM32H503 in our application. Due to size constraints in the PCB dimensions, we are going with internal clock for both MCU & internal RTC.

Since, internal clock is used, the frequency given to the internal RTC ranges from 29.4 kHz to 33.6 kHz. So, instead of 1s, due to the clock accuracy, 0.91s to 1.03s will be the actual value. We would like to know, what would be the RTC drift per month or per year with this internal clock accuracy.

Kindly guide us in this regard.

Best Regards,

Prahaladh S

[TDK]

It would have a drift of -66 to +22 hours per month hours per month. So pretty unusable. The LSI is just not accurate.