PMIC POR open drain signal voltage - 2.65V instead of 3.0V

[Karthik37]

1. In our iMX6 SOM, we tried to check the POR working behaviour.

In our testing, we probed the RESETBMCU signal from the PMIC that gets connected to iMX6 POR signal. When tested, we observed the voltage appeared to 2.65V (we probed the voltage using oscilloscope when the board boot up is finished and Operating System is launched). But it should be 3.0V (VSNVS).

Since RESETBMCU signal is an open drain signal and it connected directly to iMX6 processor POR signal, we should get 3.0V (POR signal is internally pulled up to VSNVS). We also checked VSNVS voltage and it measured 3.0V.

We also checked with errate regarding this problem. Did anyone encounter any problem like this.

PMIC connection details

PMIC Part Number: MMPF0100F0AEP

PMIC Pin Number: 3

PMIC Pin Name: RESETBMCU

PMIC Pin type: Open Drain

Connected to:  iMX6 connection details

iMX6 Part Number: MCIMX6Q5DVT12AC

iMX6 Ball Number: C11

iMX6 Ball Name: POR (internally pulled up to VSNVS voltage)

Thanks,

Karthik R

[JorgeRama_rezRi]

Hi Karthik,

Strictly speaking, POR is pulled up to VDD_SNVS_IN, so you
must make sure this voltage is supplied with PMIC VSNVS so your voltage level
is 3.0. It is allowed to supply VDD_SNVS_IN with a different source as long as
the voltage and power up sequence requirements are met, but in this case, the
RESETBMCU pin must be pulled up to this other source. Are you connecting
VDD_SNVS_IN to PMIC VSNVS?

I’d also recommend to check all other connections of the POR
pin just to make sure nothing is lowering the voltage. Do you have anything
else connected here? Have you tried disconnecting anything and just leaving
RESETBMCU connected to POR?

Best regards.

Jorge.

[Yuri]

Please check if there are other sources of the POR signal on the board.

[igorpadykov]

Hi Karthik

there are no known issues with these signals levels, which

could explain this behaviour.

If this is just one board, most probably silicon structure is damaged

(due to ESD shock, thermal overheating). If there are several boards, probably

there is layout error and this signal is shorted to some other. You may

wish to carefully check (may be X-ray screen) layout.

Best regards

igor

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