PMIC_ON_REQ state after SNVS on imx8mp

[diegoperez]

Hi,

I am trying to figure out the first power up of the imx8mp.

I am implementing the powering of the imx8mp with PMIC PCA9450C, I want not to use ONOFF signal of the imx8mp because in my application there is not a power button.

According to the PMIC datasheet, PMIC_ON_REQ must be high to go into “PWRUP Seq” state.

• What is the state of PMIC_ON_REQ (F22 ball of imx8mp) after PMIC enters SNVS state?
• If state is low, Am I forced to set ONOFF low to get PMIC_ON_REQ high?

Thanks and BR.

Diego.

[Yuri]

@diegoperez 
Hello,

   1) the state of PMIC_ON_REQ  after PMIC enters SNVS state is not changed;
   2) it is needed  to set ONOFF low to get PMIC_ON_REQ high.

Regards,
Yuri.

[diegoperez]

Hi @Yuri , thanks for your reply.

I don’t want to use a power button. In my application the system needs to be run after 12V main power supply is applied, without touching any button.

So, according your answer, will I need some electronic to generate a low pulse in ONOFF signal when SNVS is powered to set high PMIC_ON_REQ?

According to datasheet PMIC_ON_REQ has pull up at reset so PMIC will enable all rails, but in table “6-39 Power mode transitions” there is a sequence for the power mode “ON, first time” that says the power button is pushed to set PMIC_ON_REQ high.

[Yuri · Accepted solution]

@diegoperez 
Hello,

  Note: At the first power up, i.MX8M PMIC_ON_REQ signal is asserted when
i.MX8M SNVS voltages (VDD_SNVS, NVCC_SNVS) appear (without ONOFF button).

Regards,
Yuri.