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# 1   2008-09-24 18:47:35 RTC Alarm OUT pin, is it possible?

Jay2
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Registered: 2008-09-24
Posts: 3

RTC Alarm OUT pin, is it possible?

Hi!

My application need to go into deep sleep for long periods, and self-wake.
Of course, we can stop everything but the RTC. In such a situation, I need the RTC to somehow enable the power supply on RTC alarm.

If I understood correctly, from document RM0008 [Family reference], section 5.4.2, the ASOE and ASOS bits permit this behaviour:
Once the device is in sleep, and the only power to device is from VBAT [VDD disconnected], the device will output a logic high for 1 RTC cycle on RTC alarm on pin TAMPER [PC13 on STM32F103ZET6].
Is it correct? Is the TAMPER pin capable of output in the backup domain? Or does it need the device to have power to be able to ouput the pulse? How much mA can it sink/source while in battery mode? What voltage will appear on the pin? VBat-0.7 ?

I know this information is probably well written in some documentation, but I don't seem to be able to find it!

Thanks a lot,
-Jay

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