In the combination of PF8100 and i.MX8, what is the behavior in case of thermal shutdown on PF8100?

[YukioOyama]

Hello,

I have purchased and am using a board already configured with an i.MX8QM and a PF8100.

Please give a brief description of the thermal shutdown operation of the PF8100.
In the PF8100_PF8200 datasheet, if I look at the 13. state machine Figure.5 State diagram, the Z transition starts when a shutdown fault occurs. In PF8100, after the Z transition, the fault state goes from S->U to LP_Off.

At this point, does NXP's Linux (i.e. i.MX8) do the PF8100 to do anything?

If i.MX8 does nothing, I assume that if the temperature cools down, the PF8100 will go from F->L to PowerUpSequense, is this correct?

Or does NXP's Linux perform some action to the PF8100 that produces a different result?

Best regards,

Yukio Oyama

[Dhruvit]

Hi @YukioOyama,

I hope you are doing well.

-> Nonfaulty turn-off events: move directly into LP_Off state as soon as the power-down sequence is finalized.

->The LP_Off state is a low power-off mode selectable by the LPM_OFF bit during the system on modes. By default, the LPM_OFF = 0 when VIN crosses the UVDET threshold, therefore the state machine stops at the LP_Off state until a valid power-up event is present. When LPM_OFF= 1, the state machine transitions automatically to the
QPU_Off state if no power-up event has been present and waits in the QPU_Off until a valid power-up event is present.

->CTRL1 This register is Writing a 0 and disables the thermal monitor, preventing the thermal interrupts and thermal shutdown events from being detected.

->As the temperature crosses the thermal thresholds, the corresponding interrupts are set to notify the system. The processor may take appropriate action to bring down the
temperature (for example - r by turning off external regulators, reducing load, or turning on a fan).

-> When the shutdown threshold is crossed, the PF8100/PF8200 initiates a thermal shutdown and it prevents from turning back on until the 15 ºC thermal shutdown hysteresis is crossed as the device cools down.

I hope this information helps you!

Thanks & Regards,
Dhruvit Vasavada

[YukioOyama]

Hello Dhruvit-san,

I thought PMICs had a fixed behavior distinguished by OTP program ID. But according to your answer, I thought PF8100 is supported by the processor. Which source code of NXP's Linux BSP controls PF8100?

I wish that mechanism were that simple.

Best Regards,

Yukio Oyama

[Dhruvit]

Hi @YukioOyama,

->When the PF8100 enters thermal shutdown, it will first enter the S->U fault state. If the temperature does not cool down within a certain period of time, the PF8100 will then enter the LP_Off state. In this state, the PF8100 will power down all of its internal circuitry, including the processor.

->Linux BSP does not perform any specific action to the PF8100 when it enters thermal shutdown. However, the Linux kernel does monitor the PF8100's temperature and will take appropriate action if the temperature exceeds a certain threshold.

->The PF8100's behavior is controlled by the OTP program ID, which is a unique identifier that is burned into the chip during manufacturing. The OTP program ID determines the PF8100's operating voltage, clock frequency, and other parameters. However, the PF8100's thermal shutdown behavior is not affected by the OTP program ID.

The source code of NXP's Linux BSP that controls the PF8100 is located in the drivers/power/pf8100 directory. 

This directory contains the PF8100 driver. Please refer to that

I hope this helps!

Thanks & Regards,

Dhruvit Vasavada

[YukioOyama]

Hello Dhruvit-san,

Thanks for your explanation.

I have looked for the directory you indicate in the Linux BSP. But it was not there.

https://github.com/nxp-imx/linux-imx/tree/lf-6.1.y/drivers/power

Am I looking in the wrong place? Please send me the URL of the directory you indicate.

Best Regards,

Yukio Oyama

[Dhruvit]

Hi @YukioOyama,

Please accept my apology for the inconvenience.

Please look at this path.
/driver/regulator/pf8x00-regulator.c

/driver/regulator/Kconfig

Thanks & Regards,

Dhruvit Vasavada

[YukioOyama]

Hello Dhruvit-san,

I found the regulator settings for the PF8100 in the directory you indicated. But that was not what I wanted to know.

What I would like to know is if after a thermal shutdown occurs on the PF8100, if the temperature drops, the system will automatically reboot without any trigger from the user.

According to the PF8100 datasheet and your description, after the PF8100 state is transitioned by thermal shutdown, one of the conditions for proceeding to the next state is that the host asserts the PWRON event.

If the host itself is healthy, is this PWRON event asserted by the host after thermal shutdown of the PF8100? Or does the host keep PWRON (=PMIC_ON_REQ) enabled regardless of the PF8100? In the first place, is the PF8100 supplying power to the host then?

After the PF8100 has thermal shutdown, I would like to know if the host asserts the event or if the PF8100 does any action to the host or waits for the user, I would like to know who will move the state next.

Best Regards,

Yukio Oyama

[Dhruvit · Accepted solution]

Hi @YukioOyama,

I hope you are doing well.

Please accept my apology for the delayed response.

->After a thermal shutdown occurs on the PF8100, the system does not automatically reboot without any trigger from the user or external system.
->It enters a thermal shutdown state when the temperature exceeds a certain threshold to protect itself and the system from overheating.

->The PWRON event (also known as PMIC_ON_REQ) is typically used to request the PF8100 to power on or off the system. It is generally controlled by the host, and the host is responsible for asserting this event to initiate the power-up sequence.
->The PF8100 will not automatically reboot after a thermal shutdown. The host must assert the PWRON event in order to proceed to the next state. This is because the PF8100 is in a low-power state after a thermal shutdown, and it cannot be powered on without the host's intervention.

For more information please refer to the below link
https://www.nxp.com/docs/en/data-sheet/PF8100_PF8200.pdf

Thanks & Regards,
Dhruvit Vasavada

[YukioOyama]

Hello Dhruvit-san,

I understood from your explanation that PF8100 needs a trigger from i.MX8 to power up again. I was not sure which would work first since the PF8100 and i.MX8 are connected to each other.

We want our system to reboot on its own from a fault with HW, so not rebooting on its own gives us a new challenge. But I understood how the device works. Thanks.

I will close this case.

Best Regards,

Yukio Oyama