Asus FA507 not charging the battery on main supply, only charing on USB-C.

[FrozenHaxor]

Hello, I have DA0NJSMBAD0 board that has dual charge ICs, one of them is BQ24800 and the other is ISL8238CH

Now this is a very peculiar design, they're using the BQ to charge from the main 240W power brick path, and the ISL to charge from USB-C PD port.

The ISL side works fine, but the BQ side does not. Battery is good.



I have swapped it for BQ4780S as it's essentially an older version of the chip and there was no change. I get 19V VCC to the BQ, and the ACOK is 3.15V

Any insights into what this could be?

[mon2]

ACN = 18.7V
ACP = 19.5V

This does not look right. There is a close to 0 ohm resistor across the ACP & ACN pins that is used for the current sensing. Respectively, the voltage on each pin should be very close. Double-check this measurement again.

[mon2]

There our countless cases of the same on this forum based on the BQ / Texas Instrument charger IC.

Download a datasheet for this part.

Check the voltage to ground of:

ACDET
REGN
ACN / ACP
ACDRV

Post the list with their pin function name for a review. As noted in the above sticky by piernov - study the DCin mosfets that precede the ACN / ACP pins. If ACDRV is not ~25v then one of these mosfets is most likely defective.

[FrozenHaxor]

Check the voltage to ground of:

ACDET
REGN
ACN / ACP
ACDRV

Post the list with their pin function name for a review. As noted in the above sticky by piernov - study the DCin mosfets that precede the ACN / ACP pins. If ACDRV is not ~25v then one of these mosfets is most likely defective.

ACDET = 2.6V
REGN = 6V
ACN = 18.7V
ACP = 19.5V
ACDRV = 25.4V

The laptop works and powers on, just isn't charging on this BQ IC, charges fine on the ISL when plugged to USB-C though.

[mon2]

ACN = 18.7V
ACP = 19.5V

This does not look right. There is a close to 0 ohm resistor across the ACP & ACN pins that is used for the current sensing. Respectively, the voltage on each pin should be very close. Double-check this measurement again.

[FrozenHaxor]

This does not look right. There is a close to 0 ohm resistor across the ACP & ACN pins that is used for the current sensing. Respectively, the voltage on each pin should be very close. Double-check this measurement again.

Good insight, I only traced one current resistor to the ISL but didn't do it with the BQ as there are two of them, turns out there is internal trace broken to one sense pin, ran a wire and the readings are normal, charging came back.


Thank you for the help.