Dell Inspiron 5570 / LA-F115P AC Adapter not detected

[FrozenHaxor]

Hey, I have a diagnostic dead end with this one.
Laptop had destroyed DC IN jack, most likely shorted the 1Wire bus to +19V since PD1 protection diode was burnt to crisp, nothing else appears damaged. Removed the damaged diode for test and replaced power jack, used known good power supply for testing and the laptop powers up, in BIOS it shows "AC Adapter = Not Installed" so a bit unusual, usually they show up as Unknown power so I assumed it completely doesn't detect AC IN somehow and sure enough the entire +3.3V_VBUS_IN is dead, no short. There is no +CCG_VBUS present either, AC_OK signal is around ~2V. PQS01 MOSFET is good but does not get power to the gate. Traced it to UT7 chip that's supposed to control it, but it doesn't have anything on any of it's pins either.

According to the power control diagram, it's supposed to get a signal from UT1 with signal OVP_TRIP_P1 and VBUS_P_CTRL_P1



Now there is 0V on both of those. I lifted the Enable pin leg of UT7 and pulled it to 5V for test, the PQS01 turns on, both +CCG_VBUS and +3.3V_VBUS_IN are present, but laptop won't start, it's unhappy about the little uncommanded power detour. Turns off after few seconds.

Is UT1 bad? Is something else responsible for this? I feel like I went too far into the rabbit hole and missed something earlier but I can't find anything. Any ideas? Nothing jumping out at me at thermal survey, +19V rail consumption is normal at 0.4A while in BIOS, fan cycles from time to time.

Board pics:



Thanks for any suggestions! Schematic and Boardview (works in BoardViewer) attached.

[crowntoy99]

Re: Dell Inspiron 5570 / LA-F115P AC Adapter not detected

what about psid voltage ?

https://www.youtube.com/watch?v=L5v4hT0PRKI

[Yousuf]

Re: Dell Inspiron 5570 / LA-F115P AC Adapter not detected

Hi, With laptop booted up, can you exercise any PD bits to see if UT7 is working ? (like charging the laptop using the USB c cable or charging a device like phone through the USB c port). The OVP_TRIP_P1 is active low so in normal case this should be driven high but I understand you have seen this signal low ?.

[FrozenHaxor]

Re: Dell Inspiron 5570 / LA-F115P AC Adapter not detected

what about psid voltage ?

https://www.youtube.com/watch?v=L5v4hT0PRKI

PS_ID and PSID are at 3.3V

I have 434mV at the base of PQ2, which appears to be spot on from the voltage divider calculation - not sure where the guy on video got the "always 48mV" from.

Hi, With laptop booted up, can you exercise any PD bits to see if UT7 is working ? (like charging the laptop using the USB c cable or charging a device like phone through the USB c port). The OVP_TRIP_P1 is active low so in normal case this should be driven high but I understand you have seen this signal low ?.

I have pulled the Enable leg of the UT7 high (to +5V) to test, and it works fine, rail gets powered up but the board doesn't like the bypass and shuts down shortly.

[mcplslg123]

Re: Dell Inspiron 5570 / LA-F115P AC Adapter not detected

Have you checked the voltage divider resistors for ACOK?? ACOK must be 3V as you are aware and i think unless acok is fixed,it wont work.

[jatoi]

Re: Dell Inspiron 5570 / LA-F115P AC Adapter not detected

+CCG_VBUS not found, how many volts on this point?
if 19v then 3.3v regulator enable all charging section.. +CCG_VBUS volts?

[Yousuf]

Re: Dell Inspiron 5570 / LA-F115P AC Adapter not detected

PS_ID and PSID are at 3.3V

I have pulled the Enable leg of the UT7 high (to +5V) to test, and it works fine, rail gets powered up but the board doesn't like the bypass and shuts down shortly.

Sorry I could have made it clearer. I was trying to reply to your question on whether UT1 (CYPD4125) is faulty. You might already know this, but for the sake of clarity - The main function of UT1 is that it does power delivery (PD). The chip itself is an ARM-based microcontroller with flash and ROM. So to check if this chip is working, the best way I think is to exercise PD, like charging through a USB C or charging a fast-charging capable phone, and see if the chip (UT1) can do fast charging.

As for OVP_TRIP_P1, it is active-low signal and if the chip detects an over voltage then it should drive it low, otherwise for normal operations, it should be high, switching QT5 ON, thereby passing VBUS_P_CTRL_P1 to enable pin of over current protector chip UT7. So there is a kind of logical AND operation happening where VBUS_P_CTRL_P1 AND OVP_TRIP_P1 should be high for OC chip to be enabled.

Therefore I believe the chip (UT7) will be enabled only if discharge operation is active (as in you have plugged a device into the usb port). Can you measure these signals (OVP_TRIP_P1 and VBUS_P_CTRL_P1) by plugging a USB device?

As others have replied you need to check ACOK.

Regards

[FrozenHaxor]

Re: Dell Inspiron 5570 / LA-F115P AC Adapter not detected

Have you checked the voltage divider resistors for ACOK?? ACOK must be 3V as you are aware and i think unless acok is fixed,it wont work.

ACOK measures around 2V, according to the voltage divider on the schematics that's spot on. Added my measurements to a screenshot of part of schematic.

ISL9538 pin 24 ACOK "ACOK_CHG" = 3V

AC_PRESENT signal is 3,3V
ACAV_IN1 is 3V

Sorry I could have made it clearer. I was trying to reply to your question on whether UT1 (CYPD4125) is faulty. You might already know this, but for the sake of clarity - The main function of UT1 is that it does power delivery (PD). The chip itself is an ARM-based microcontroller with flash and ROM. So to check if this chip is working, the best way I think is to exercise PD, like charging through a USB C or charging a fast-charging capable phone, and see if the chip (UT1) can do fast charging.

As for OVP_TRIP_P1, it is active-low signal and if the chip detects an over voltage then it should drive it low, otherwise for normal operations, it should be high, switching QT5 ON, thereby passing VBUS_P_CTRL_P1 to enable pin of over current protector chip UT7. So there is a kind of logical AND operation happening where VBUS_P_CTRL_P1 AND OVP_TRIP_P1 should be high for OC chip to be enabled.

Therefore I believe the chip (UT7) will be enabled only if discharge operation is active (as in you have plugged a device into the usb port). Can you measure these signals (OVP_TRIP_P1 and VBUS_P_CTRL_P1) by plugging a USB device?

As others have replied you need to check ACOK.

Regards

Tested by fast charging a modern phone through USB C output as you requested.

OVP_TRIP_P1 = 3,17V
VBUS_P_CTRL_P1 = 3,17V
HW_ACAV_IN = 3V (without the phone on charge this point is 0V)

UT7 is enabled with 2,2V on it's EN pin. BIOS still reports "AC Adapter = Not Installed". Phone fast charges properly.

When I disconnect the phone, the board shuts down instantly as if I pulled the adapter out.

+CCG_VBUS not found, how many volts on this point?
if 19v then 3.3v regulator enable all charging section.. +CCG_VBUS volts?

+CCG_VBUS is 0V but when I connect a phone to start the fast charging circuit, it goes to 5,1V.

[Yousuf]

Re: Dell Inspiron 5570 / LA-F115P AC Adapter not detected

Thanks for the measurement. So it checks out that the UT7 works for discharging - charging a device. Did you try plugging a usb-c fast charger (not device) to the laptop to see the other way around ? In that case does the BIOS report anything different ?

[FrozenHaxor]

Re: Dell Inspiron 5570 / LA-F115P AC Adapter not detected

Thanks for the measurement. So it checks out that the UT7 works for discharging - charging a device. Did you try plugging a usb-c fast charger (not device) to the laptop to see the other way around ? In that case does the BIOS report anything different ?

When I plug in a Power Delivery adapter to the USB C port while in BIOS (laptop powered by the still undetected dell plug) it says AC Adapter=60W

I also am able to power up the board with just the PD adapter, although the board complains that the adapter is not 65W or above. I am also able to charge the battery through the PD adapter and the board recognizes the battery properly, also switches between battery power and PD power properly.