Unexpected DC voltage observed on SW2LX of MMPF0100

[torus1000]

Hi,

Now we are observing VDDs of our i.MX6Q custom board.

Just after shutdown command issued from console but PMIC VIN still kept alive,

we expected all SW regulators  fell to 0V but SW2 kept 1.4Vdc without any PWM/PFM switching noise.

(SW1,3,4=0V, SW2=1.4V, SWBST=0.7V)

Have ever someone heard same curious phenomenon? Is it correct behavior?

We knew SW2LX(MMPF0100F0 pin22) connected to GEN_3V3(NVCC_LCD/EIM/GPIO/SD/NAND/JTAG)

but current direction seems from PMIC to NVCCs.

Can anyone help us?

[Yuri]

Strictly speaking - under Linux - it is needed to issue

the following command

# shutdown -h now

(-h : Poweroff the system)

or

#poweroff

~Yuri.

[Yuri]

Hello,

From the team :

  " Just after shutdown command issued from console but PMIC VIN still kept alive,

we expected all SW regulators fell to 0V but SW2 kept 1.4Vdc without any PWM/PFM

switching noise. (SW1,3,4=0V, SW2=1.4V, SWBST=0.7V)”

  Normally PMIC will not have this issue, this 1.4Vdc may be some leakage from other rails,

you need to check the all the nets connected to SW2.

Regards,

Yuri.

[torus1000]

Dear Yuri

We checked the current direction with additional diode as following.

Our result seems not leakage but SW2 output.  Please see attached waveform-B.

Is there any idea to kill SW2 during shutdown?

It doesn't matter STANDBY assert or not.

Thank you for your help.

BR

[Yuri]

Hello,

   To check if we have a leakage effect (or strong voltage),

please try to pull down SW2 output via 50 - 100 Ohm resistor
during short time after power down.

Regards,

Yuri.

[gusarambula]

Yuri​, would you rather have a Case to review this case and receive further information? Please look at the follow up information from torus1000 in the meantime.

torus1000​, would it be possible for you to create a Case to follow up on this matter? We rarely review schematics on the communities as it is often sensitive information. You may use the link provided by Yuri.

Regards,

[Yuri]

Hello,

  it may be some kind of leakage in the case. Is it possible to look at the

schematic. You may create request to provide it.

How to submit a new question for NXP Support

Have a great day,
Yuri

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