Lenovo E15 Gen.3 NM-D481 No starting and charging via USB-C, The device starts only via the battery.

[master3112]

I have a Lenovo E15 Gen.3, motherboard NM-D481 with a defective USB-C port. The device starts with battery. When connected to the USB-C power supply, it does not start or charge. 20V is present at the input of the UT5 (High voltage USB PD power switch), 0V at the output
UT5 pin 3 (SNK_PS_EN) =0V
RPT3 Pin1+2 LDO 3V3 present
I suspect that the UT2 USB-C power controller is defective because the UT5 is only controlled by the UT2. However, the UT2 supplies on pin 33 (+LDO_3V3) which makes me wonder if it is defective after all. Unfortunately I don't have it here to test it.
Has anyone had behavior like this?
THX

[mon2]

Link a schematic.

My schematic for the NM-D481 contains a WLCSP packaged device @ UT5 so there is no pin 3.

[master3112]

Its Pin A3

[mon2]

Ok - we have the same schematic but the BV is referencing the pins in a strange order. They should be using the schematic pin names.

So pin #3 = A3 on the WLCSP package and is an active LOW signal (denoted by the # suffix). When this pin is LOW = 0v, the signal is active and is being requested to pass the voltage through the load switch.

You have 0v = OK to enable and pass the voltage through.

To confirm, you have voltage going IN to this load switch but not OUT of the load switch?

Remove all power. Measure the resistance to ground at the output of this load switch. This can be done at any of the VINTx pins. What is the resistance?

If the resistance is too low, the switch will not be able to handle the excessive load and turn off or is now defective.

See attached.

[master3112]

I have 3M ohm at the output of the UT5.
I have 20V at the input of the UT5.
So the UT5 is defective and don´t switch?
Can I manually feed 20V into the output of the UT5 to test whether the device starts? Normally I can't damage anything, can I?

[mon2]

Agree, output is not shorted so I would think it is safe to bypass it. To be safer, do not connect the battery for this test. Only the power adapter to the board power path is of interest.

To me, this load switch is defective and needs to be replaced for a fix.

[master3112]

mon2 thanks for you input.
I did not know that this component is open when 0V voltage is applied. Your tip has helped me a lot and I have learned something again.
I will order the NX20P5090UK and replace them. I will give feedback as soon as I have completed the repair
THX

[mon2]

Good. Suspecting that the internal mosfets are defective.

Here is a truth table for this part and the highlighted case that is for the normal operation on your board.

[master3112]

Hello mon2,
I have now received and installed the NX20P5090. The device is working again.
Thank you for your support.

[mon2]

Very good to hear. Thanks for the positive update.