AGX RTC retention issue

Autonomous Machines Jetson & Embedded Systems Jetson AGX Xavier
1

Hi Expert,

We are using RTC as as system clock and VDD_RTC is supplied by a battery. We ran into two issues

  1. Sometimes the RTC will stop after AGX poweroff depite there is a battery. If RTC ever stopped, the RTC will be always back to the time of stop in the future use of the module.
  2. poweroff the system, then disconnect the RTC for several minutes, and connect battery again, the same issue can be reproduced. It seems the time never can be saved if RTC ever stopped.
    We reply on RTC for our application, so RTC feature is critical for us.

Thanks
Peter

4

Hi, to keep RTC time, it needs to keep power supply of RTC battery/capacitor all along as there is only a small capacitor in module for it. Have you checked the voltage level of RTC battery/capacitor during whole test? It should be >2.5V to the BBAT pin.

5

Thank you. The issue may be the sync issu between system time and RTC time (hwclock).

Peter

7

Hi, Trumany,

What’s the current consumption of the VCC_RTC? We need to check battery life based on it. We haven’t seen this parameter in datasheet.

Regards
Peter

8

It’s about 2uA. You can search topics in forum first, there are many similar topics in which you can find the answer of general questions.

9

Thanks Trumany. Even there is a battery connected, but the PMIC RTC is occasionally reset to default, what’s the possilbe cause?

Peter

10

Are you sure the voltage level of BBAT is stable all along? If so, do you have log file to show any abnormal action when this happen?

11

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