BQ 727 Chip 2.4V at Phase

[Axis937]

HI folks 1 question on ablout BQ 727 IC. I believe that it is also meant to charge the battery based on the proximity to the battery pins. I have a strong feeling that the battery is dead but i will look at it later. My question is VCC on BQ is receiving the ADP voltage of 19V. However PHASE and HiDRV on BQ is only pushing out about 2.4V with or without battery attached. That 2.4 V is heading to the gate of the charging mosfet. Source is also pushing out the same 2.4V. Finally the battery voltage pin is receiving 2.2V. Do you see this as a issue or no issue. Battery is likely faulty as well as earlier mentioned.

1. Why is it pushing out only 2.4V?
2. What triggers it to push only 2.4V
3. Where could the problem be?
4. By adding a working battery, will it alter the Phase and HiDRV voltage?
5. Does the battery SCK SDA or System present pins play a role in the above issue?

[mon2]

The BQ727 uses N-channel mosfets for the DC-in power path and the battery charge / battery mosfets. Respectively, the gate voltage should be higher than the voltage being passed between source/drain pins to enable the mosfet.

Remove all power. Meter in resistance mode. For each mosfet linked to this charger IC, review the resistance across the mosfet pins.

Source (1-2-3) & drain (5-6-7-8)
source (1-2-3) & gate (4)
gate (4) & drain (5-6-7-8)

Post each measurement. Is there a schematic for your logic board? Which brand? Which model? What are the silk screenings on your logic board? It may not matter but will be helpful.

Focus on the power path mosfets and the battery charge mosfets (high & low side mosfets driven by this charger IC). What is the voltage of REGN to ground? It should be ~6v.

Review the charger circuit sticky above by piernov.

[Axis937]

This is a VAUS5 LA9001P Rev 1 board. I managed to find v 0.3 only. But it seems to be very identical.
The drain /source/ gate readings are in 200kohms and above going into Megaohms. I dont think there is any short over there. Correct me if i am wrong as i am a super duper newbie.

What does silk screening mean?

Regn to ground is 6V

[mon2]

Silk screen = white text on the logic board such as 'LA-9001P' to identify the board.

A good mosfet will be high hundreds of k ohms on the resistance. At 200k, is of concern. Whichever mosfet reported this measurement, consider to carefully flux and remove the mosfet off the logic board. Protect nearby parts from flying off the board and/or melting.

Once the removed part is cooled, measure it again while it is on your work bench. If still ~200k ohms, replace it. Post the exact measurement of the mosfet that has this relatively low resistance.