RTC clock source imx8MP vs 8MM

[sfatyushkin]

Hi all!

Previously, we made a device on imx8MM, and there a 32 kHz signal from the PMIC output was connected to RTC_XTALI (as in EVK on 8MM).
Now we are making a device on imx8MP, made the same connection, but PMIC does not start (there are no clock pulses at the C32K_OUT output, there are several pulses of about 20 ms duration at PMIC_ON_REQ at startup).
We see that in EVK on imx8MP a separate generator is connected to RTC_XTALI. Is this important and is this our problem?

BR, Serge

[JorgeCas]

Hello,

The connection should not be an issue, please check that PMIC_ON_REQ is asserted correctly.

In PMIC side, please confirm that is detecting a valid clock and halt in crystal.

Best regards.

[sfatyushkin]

Problem solved. It was not RTC clock source.
We used BD71847AMWV on the product prototype to power the IMX8MP by combining BUCK1 and BUCK5. Feedback for BUCK5 initially was connected to GND (the same idea as in recomended PMIC PCA9450C for R_SNSP3_CFG, but wrong). When feedback for BUCK5 was reconnected as feedback, PMIC started up and works.