Internal RTC current usage

Hi, good day!

I am currently using iMX8QP and in page 46 of datasheet (, it mentioned:

May I know what is the typical current consumption of the Internal RTC? I am using this battery ( as VCC_BACKUP, may I know how long this battery is expected to function?


According to NXP datasheet internal RTC power consumption is 50uA. The mentioned battery has a 35mAh capacity. So in ideal case it should last around 700 hours or 29 days. But in reality I’d expect something around 500 hours.

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Hi @alex.tx ,
I have a follow up question on this topic. I tried to use a SMU as the VCC_BACKUP, but I only see it draws around 0.6uA, which is around 100 times smaller than the spec
Is this a normal behavior?

Hi @alex.tx , do you have any insight for this? Thanks

Was RTC enabled? Was main module’s power switched off?

@alex.tx ,

Can you share more details in how to enable to Internal RTC ?

Note : We are using Yocto BSP provided by Toradex, anything need to be done from here ?

Below is the details:

terminal command : timedatectl status

terminal command : hwclock -r

terminal command : dmesg
dmesg.txt (31.1 KB)

Note: We dint connect external RTC chip, so the below line is expected. (We want to test internal RTC)
rtc-ds3232: probe of 18-0068 failed with error -5

Also found all these in the directory

internal RTC should be enable by default if you are using Toradex provided BSP.

Was Apalis module being powered ON when you did VCC_BACKUP consumption measurement?

No, Apalis was not powered ON. I just connect the VCC_BACKUP when I am doing the measurement.

Was RTC running? I.e. keeping correct time when module was unpowered.

Yup, if VCC is off and VCC_BACKUP present, the RTC Time will continue the counting. If no VCC_BACKUP and VCC is off, the RTC time will reset

We haven’t done any power consumption measurement related to internal RTC. NXP datasheet defines maximum of 50uA RTC consumption. Looks like actual consumption is lower.

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Noted, Thanks!