RTC in WP7502 speeding 10 minutes an hour on backup battery


#1

Hi,
We start to use RTC coin 3V battery connected to BAT_RTC pin to keep time in case the main power supply is disconnected. It works, but inaccuracy is surprising - more then one hour during 8 hours.
I cannot find RTC accuracy specification in WP7602 data sheet. Is it the reason why battery components are not assembled on Redboard?
And one note to R306 value (10k) - average consumption I can measure is 5 uAmps as declared, but there are 30 ms current pulses up to 150uA which can make significant drop on BAT_RTC.

Please help or explain.
Thanks!
Mirek

UPDATE:
I can confirm that described problem with very inaccurate RTC is also similar at WP8548 module. I have not found infulance of FW version.
In addition, I have found that the consumption from a 3V battery reaches values > 150uA periodically for tens of seconds.
I have encountered also serious problem when Module cannot start after re-connection of main power supply and has to be recovered.
So guys, has somebody use 3V RTC battery?

Thanks

Mirek


#2

Hi! I have tested MangOH Red with WP7702 and unlike the WP7502 RTC doesn’t seems to work at all after removing the main power. It always starts at 06 Jan 1980 …


#3

Will check whether internal RTC was removed on WP77 and get back to you