While hunting for shorts in the vicinity of the IC charger, I found this capacitor circled in green on the figure with a resistance of 0.4 Ohm...maybe a little low in value. Could this value explain the exclusion of the adapter as a power source?
I read @Piernov's trhead, very interesting and as he suggests I also measured the resistance connected to the CMSRC output and it's ok, the mosfets are all ok... as an electronics hobbyist though to think that the adapter doesn't deliver enough current but I tried 3 of them and the current comes out in abundance.
Is there something that prevents the adapter from not having priority when connected together with the battery.
Correction, before I measured wrong maybe the tip didn't touch well and was unstable, now I'm sure that between pin 1 ACN and 2 ACP there are 0.8 Ohm stable
These 2 pins correspond to the two sides of the sensing resistance, if I measure directly on this resistor I find 0.2 Ohm, probably the extra 0.6 more will be due to the traces (?)
this operation worries me because I have already tried to remove some mosfets with hot air but I didn't want to insist because it seemed to me that too much time had passed and it would not come off-
But by measuring I see that PQ201 with the red lead on the source and the black lead on the drain is open and on the contrary I have the threshold voltage of 0.51 V, can it be deceiving?
See attached. The voltage @ PHASE pin #19 to me is of concern.
This is the voltage created by both the high side mosfet (PQ201) and low side mosfet (PQ202) working together to lower the high adapter voltage that is fed into the drain pin cluster (5-6-7-8) of PQ201.
When the adapter only is connected I would not expect a voltage to be present on pin #19 that monitors the lower voltage.
For now, test the following ideas:
Remove the 0 ohm resistor @ PR217. This will remove the gate voltage on PQ201.
Then measure again the voltage to ground of BQ24725_LX. You can measure at the BATT+ battery connector pin. Do not have the battery connected.
What voltage do you read now ?
In summary, we want to disable PQ201 from the circuit.
When the adapter only is connected I would not expect a voltage to be present on pin #19 that monitors the lower voltage.
What voltage do you read now ?
In summary, we want to disable PQ201 from the circuit.
I wanted to let you know that having also the motherboard of the P850, identical to this one, also on this one the voltage is the same, that is 3.08 V, when there is only the adapter, the same also on pin 18 of BQ24725_LX
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