RTC design recommendation

gsantha · ‎2011-11-27

Posted on November 27, 2011 at 19:53

Hi!

In my recent design I'd like track the time/date using the RTC peripherial of the STM32L152. If I'm not wrong, the RTC is only active when the MCUs power supply is on. I want the clock to run during powered down periods. How can I do that? Well before I was using external RTC chips equipped with backup battery VBAT power pins - has the STM32L152 VBAT pin or any similar?

Thanks, Greg73

Tesla DeLorean · ‎2011-11-28

Posted on November 28, 2011 at 20:06

The presumption is that the STM32L152 is running off a battery. Put it in STANDBY, it will turn off VCore and it should draw a few uAmp with the RTC ticking off LSI.

You'd put a battery and charger circuit upstream from the device.

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gsantha · ‎2011-11-30

Posted on November 30, 2011 at 15:04

Thank you clive1. It is certainly a decent approach however I don't really like the idea to implement a battery charger subcircuit. I'm experimenting with diode ORing right now.