Auto power on in I.MX6Solo with PMIC (MMPF0100)

[shichinhuang]

Hi ,

Our design need auto power on feature (without press power button) in I.MX6Solo with PMIC and also RTC coin battery apply to LICELL of PMIC (also apply to VDD_SNVS_IN of I.MX6Solo).

When I normally shut down system by press power icon of Linux and remove all power except RTC coin battery,system cannot auto power on when I apply power to PMIC next time.

I need press power button(connect to ONOFF pin of i.MX6Solo) then it can boot up. It seems PMIC_ON_REQ of i.MX6Solo deassert to PWRON pin of PMIC.

But if disconnect PMIC_ON_REQ from i.MX6Solo to PMIC,  PMIC will not power off when system normally shut down by press power icon of Linux.

Could some body help provide suggestion?

Thanks!

Shichin

[art]

The only way to auto power on the board from the state you describe seems to use an external circuit, whose function is to pull the processor's ONOFF input low when both following conditions are met:

a) the main power is removed from the system (only VDD_SNVS voltage is present);

b) the PMIC_ON_REQ signal is Low.

In these conditions, after 750ms the ONOFF input is pulled low, PMIC_ON_REQ goes High, causing PMIC to auto start up next time the main power is applied. Also, when PMIC_ON_REQ goes High, external circuit should release ONOFF from being pulled low.

Have a great day,
Artur

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[shichinhuang]

Hi Artur,

Thanks for your replied.

I did some experiments before also use the same method as you described using external circuit to control ONFF of processor,

but I found RTC coin battery will leakage from ONOFF internal pull up (VDD_SNVS_IN) to external ONFF control circuit.

So I would like to know if any method to auto power on system without contol ONOFF pin ?

Thanks!

Shichin

[art]

No, for your case, there is no way to auto power on the system other than to control the ONOFF pin. My suggestion is to design this external circuit so as it pulls the ONOFF pin down only when PMIC_ON_REQ is Low and releases the ONOFF pin once PMIC_ON_REQ goes High. This will significantly reduce the current leakage through the ONOFF pin's internal pullup resistor.

Best Regards,

Artur

[shichinhuang]

Hi Artur,

Okay.

Thanks for your reply and suggestion.

Sincerely,

Shichin