RTC AND LSI IN VBAT OPERATION

[meir3]

Posted on June 11, 2013 at 09:25

Hello!

lately i configured the RTC to work respectively to the LSI oscillator. The RTC is working well while supplied from VDD pin. when working from the VBAT the last time count is preserved but from turning off to turning on the clock doesn't advance. i went over the datasheets- and havn't encountered that the LSI doesn't work from VBAT. have i missed a configuration? can the RTC tick in VBAT mode? b.g. Chen

[Tesla DeLorean]

Posted on June 11, 2013 at 13:45

LSI isn't in the backup power domain, you must have an LSE for the RTC to work from VBAT.

[Tesla DeLorean]

Posted on June 11, 2013 at 13:55

5.1.2 Battery backup domain

Backup domain description To retain the content of the RTC backup registers, backup SRAM, and supply the RTC when VDD is turned off, VBAT pin can be connected to an optional standby voltage supplied by a battery or by another source. To allow the RTC to operate even when the main digital supply (VDD) is turned off, the VBAT pin powers the following blocks: ? The RTC ? The LSE oscillator ? The backup SRAM when the low power backup regulator is enabled ? PC13 to PC15 I/Os, plus PI8 I/O (when available) The switch to the VBAT supply is controlled by the power-down reset embedded in the Reset block.

[meir3]

Posted on June 11, 2013 at 15:35