STM32L clock battery backup

[Krenek.Steve]

Posted on July 07, 2013 at 22:56

The STM32L series does no have a dedicated pin for a battery backup to keep the RTC running when the supply is removed.

What is the recommended way to provide battery backup of the RTC for this series?

#rtc #battery-backup-stm32l

[jpeacock2399]

Posted on July 07, 2013 at 23:13

Look at the VBAT pin.  It's used to power the backup domain, including RTC and backup SRAM memory.  It works with a battery or supercap.

  Jack Peacock

[Tesla DeLorean]

Posted on July 07, 2013 at 23:56

The L series parts are designed to run from a battery, if you expect the device to keep running you're going to need to supply a voltage all the time, either by powering it by a battery with a charger circuit behind it, or split a permanent/temporal supply via some diodes, like a

http://www.nxp.com/products/diodes/switching_diodes/BAV70.html%3bjsessionid=540DB166652B4BAC6B0011DF38BE52CC?CTV=googlesem_GA_R33_BAV70&cid=prod_discretes-web_advertising_search-01_01_13

, or something along those lines.

The use of a 32.768 KHz crystal is also recommended, I think you can use other clocks in the L, but all the other STM32 series only have this clock in the backup domain.

No VBAT pin on STM32L1xx parts BTW

[tech2]

Posted on March 26, 2015 at 12:35

Sorry, my mistake.