i.MX8M Mini dual core processor RTC support

[nija_mankodi]

Hi Team, We are developing a board around 8M Mini dual core processor and PMIC PCA9450AHNY. Our product will be used in security/surveillance purpose and hence ethernet/Wi-Fi, etc. will not be connected to network.

The requirement is, if the power fails, system should retain timestamp when power will resume. Hence, we would need RTC for the same.

I understand from 8M mini dual core (MIMX8MM4CVTKZAA) datasheet that it has internal RTC module but does not support external pin for connecting super capacitor ((as we cannot use coin cell for safety purpose).

Does this mean that we will have to use I2C based RTC ICs like PCF8563 in our application? If yes, how can we know till what time RTC will keep updating its time once power if OFF?

Our requirement is to keep timestamp updated during power cuts.

Please provide your prompt support on this.

[nija_mankodi]

Noted.

Thank you.

[weidong_sun]

Hi Nija,

According to your application, you'd better choose an external RTC chip for the following reasons:
1. The built-in RTC of i.MX8MM requires 2 voltages: 1.8V and 0.8V, the usage is a bit complicated.
2. The power consumption of the external RTC chip is lower than the built-in RTC of the i.MX8MM, and the Li-coin cell battery has a longer use time.
Therefore, it is recommended that you use the External RTC + LI-COIN CELL BATTERY solution. As long as the LI-COIN CELL BATTERY has electricity, the external RTC will keep running.
Here is our RTC chip, you can choose a product that meets your requirements.

https://www.nxp.com/products/peripherals-and-logic/signal-chain/real-time-clocks:MC_71246

 Hope this information is helpful to you.

Have a nice day!

B.R,

Weidong

[AMBh]

Hi, 

I do have similar kind of application but I do not want to use coin cell for battery. I do want to use internal RTC only Can you tell me the process of how I can use it?