BD71847MWV working princible.

EErdem · ‎10-27-2020

Hello

I am designing SoM boards based on i.MXMM using BD71847MWV as a PMIC.

I want to know how PMIC knows which voltage level it should give from its output I mean when PMIC starts to generate voltage for SoC and RAM etc. I2C block which is NVCC_xxx has not got the voltage yet. This is confusing me on how it can be possible to be configured before I2C is opened.

I mean, should it opens the I2C block firstly and read the configuration register from there then open the correct order and voltage level.

Could you help me

bernhardfink · ‎10-27-2020

This PMIC from ROHM and also the NXP PMIC devices are normally dedicated devices for specific microprocessors. So they are programmed during production to start up in a specific order and with a specific voltage.

A MPU like the 8MM needs a few specific voltages at the beginning, in order to get the ARM cores and some peripherals into operation. And this is guaranteed by the PMIC. Further voltages for peripherals or even for the the DDR will come in a second stage.

So after the initial boot, the ARM executes the so called SPL (Secondary Program Loader), and there you find code which enables the I2C interface which talks to the PMIC. Then some further voltages can be switched on or adjusted before u-boot starts to load Linux.

In the NXP portfolio you can also find more generic PMIC devices, which allow you to hardcode own voltages and your own order, but for the ROHM device and also for the (of course recommended) PCA9450A from NXP the basic voltages and their order of appearance are pre-defined.

Regards,
Bernhard.

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bernhardfink · ‎10-27-2020

This PMIC from ROHM and also the NXP PMIC devices are normally dedicated devices for specific microprocessors. So they are programmed during production to start up in a specific order and with a specific voltage.

A MPU like the 8MM needs a few specific voltages at the beginning, in order to get the ARM cores and some peripherals into operation. And this is guaranteed by the PMIC. Further voltages for peripherals or even for the the DDR will come in a second stage.

So after the initial boot, the ARM executes the so called SPL (Secondary Program Loader), and there you find code which enables the I2C interface which talks to the PMIC. Then some further voltages can be switched on or adjusted before u-boot starts to load Linux.

In the NXP portfolio you can also find more generic PMIC devices, which allow you to hardcode own voltages and your own order, but for the ROHM device and also for the (of course recommended) PCA9450A from NXP the basic voltages and their order of appearance are pre-defined.

Regards,
Bernhard.