AM62L: EXTERNAL BATTERY CONNECTION TO RTC

Hi Megha Agarwal,

Thank you for your query !

Please allow me some time to internally check and discuss on the concerns to use external backup battery for the RTC in the AM62L EVK.

In the mean time you may want to check the following FAQ on the Sitara RTC topic:

FAQ on Queries related to Real-Time clock

I will get back to you with a response early next week.

Thanks for your patience !

Kind Regards,

Anastas Yordanov

Hi Megha Agarwal,

Megha Agarwal said:

Is there a reason why external battery is not connected in the EVK of AM62L. 

In the AM62L EVM, the RTC focus functionality is RTC mode or RTC + IO DDR power saving modes.

Megha Agarwal said:

Are there any limitations, if I want to connect an external battery?

Please elaborate the use case - is it only for timekeeping or to implement RTC and wakeup functions.

Regards,

Sreenivasa

Hi Megha Agarwal,

I am assuming you are aware that the AM62L SOC has x2 supplies for the RTC domain VDD_RTC (core) and VDDS_RTC.

Regards,

Sreenivasa

Hi Sreenivasa,

Yes, I am aware, and we have implemented this similar to the EVK.

Thanks,

Megha

Hi Megha Agarwal,

Thank you.

Kallikuppa Sreenivasa said:

Please elaborate the use case - is it only for timekeeping or to implement RTC and wakeup functions.

Regards,

Sreenivasa

Hi,

We want to use it for timekeeping.

Thanks,

Megha 

Hi Megha Agarwal,

Since the use case is not elaborate i am adding the below inputs.

You definitely need both power rails to remain on for RTC to operate. 

Are you wanting an RTC just to keep time when everything else gets powered off or do they want to use the wakeup functions associated with SOC internal RTC?  An external RTC is always going to be the better choice if toy just need to keep time in terms of current consumption.

Regards,

Sreenivasa

Hi Megha Agarwal,

In case you are considering implementing battery backup for the Am62L, below are the point to consider:

The power consumption of RTC-only mode is <1mW. If the customer is designing for RTC-only low power mode using an external battery, then I would not recommend using the LDOs in our EVM.

They should select discrete regulators (i.e low current DCDCs) optimized for low IQ/low power dissipation. The RTC regulators can be supplied with the battery but the remaining power ICs (like the PMIC and external 3.3V power-switch) would still need a separate pre-regulator.

Regards,

Sreenivasa