Low power mode oscillator

[Pkats.1]

Hey,

in my application, ill have an RTC function, that should work also when power in down.

From this reason, I’ll use a battery that will be connected to VBAT pin.

My question is about LSE clock.

my plan was to connect an external oscillator 32.768kHz to increase the RTC accuracy.

My question is about the oscillator in power down mode, in case that the external oscillator is powered down too.

Does the internal 32kHz oscillator start to work alternately automatically?

what is the drift of the internally 32kHz agains external 32.678kHz? Error of 1 day for a month? 1 day for a year?

Moreover, is there any recommend circuit to connect an external LSE to VBAT to with “or diode�??

thank you!

peleg

[Uwe Bonnes]

External LSE is normaly better than 50 ppm, internal is 10000ppm. LSI might be hours per day.

[Pkats.1]

Hey,

thank you.

in case I’ll use a crystal instead of oscillator, will the crystal be driven from the VBAT internally when power is down and VBAT is the only source voltage?

which solution do you recommend in case accuracy of RTC is important in low power mode?