AM4379: Power RTC in stand by.

Kiselev Dmitry

Part Number: AM4379

Hi.

AM4379 have on chip RTC. I want power to be available RTC when the main power of the processor is off. I want use battery to power supply RTS. Is it possible? If so, how can I do it?

Regards, Dmitry.

over 4 years ago

0 peaves over 4 years ago

TI__Guru 62855 points

Yes, you should be able to power the RTC from a battery while turning off the remaining device functions.

You may want to read the following E2E thread that discusses a similar topic for AM335x, while I search for AM437x specific information.

https://e2e.ti.com/support/processors/f/791/p/933504/3451826#3451826

Regards,
Paul

0 Kiselev Dmitry over 4 years ago in reply to peaves

Expert 1400 points

Hi.

Thank You for answering. I was see topic that You advised. Is it right I understand that I must use pin ad5 for RTC power supply?

Regars, Dmity.

0 peaves over 4 years ago in reply to Kiselev Dmitry

TI__Guru 62855 points

VDDS_RTC is the 1.8V power rail for the ADC.

You only need to source this power rail when the internal RTC LDO is enabled (RTC_KALDO_ENn = VSS) and the appropriate decoupling capacitor is connected to the CAP_VDD_RTC pin which connects to the LDO output and RTC core power rail.

Regards,
Paul

0 Kiselev Dmitry over 4 years ago in reply to peaves

Expert 1400 points

Hi.

Below is the implementation of the scheme according to your recommendations. Did I do everything correctly?

Regards, Dmitry.

0 peaves over 4 years ago in reply to Kiselev Dmitry

TI__Guru 62855 points

I can see you are sourcing 1.8V to VDDS_RTC and you have a capacitor connected to CAP_VDD_RTC, but not able to see if you connected RTC_KALDO_ENn to VSS. If so, your RTC power source appears to connected as expected.

Your original post shows a 74LVC1G07 being used to source RTC_PWRONRSTn, but it was not clear what is sourcing the 74LVC1G07 input. This may need to be a independent reset source if you are trying to retain RTC information when the other portions of the device is powered off.

Regards,
Paul

0 Kiselev Dmitry over 4 years ago in reply to peaves

Expert 1400 points

Hi.

Thanks for the answer. I will take into account the requirements for the reset circuit.

Regards, Kiselev.

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AM4379: Power RTC in stand by.