Figure 4-9 Working Principles Of The Ap Charging Circuit - Huawei MediaPad 10 fhd Maintenance Manual

MediaPad10 FHD Maintenance Manual

Figure 4-9 Working principles of the AP charging circuit

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Circuit analysis
The S10 uses a dedicated charging management chip Max8903 to manage the charging
process. The Max8903 chip needs only to determine whether to charge the battery. If the
battery needs to be charged, the Max8903 chip is enabled; otherwise, the Max8903 chip
is disabled. The Max8903 chip integrates a charging solution, which supports three
charging states: trickle charging, constant-current charging, and pulse charging. The
same charging circuit is used regardless of what charging mode is applied.
If the signal level of the DCM is high, it indicates that the DC input current is restricted.
The value 1 indicates that the DC input current is restricted by the IDC-to-ground
resistance. The value 0 indicates that the DC input current is confined to 500 mA or 100
mA.
CNE is used to enable or disable the charging current. It is Active-low.
IUSB is used to restrict the input current of the USB peripheral inserted into the host.
ISET is used to control the battery charging current. The maximum battery charging
current is 2 A.
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Fault analysis and location
Symptom: Two types of faults may occur on the charging circuit.
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Circuit signals
Table 4-3 lists the signals of the AP charging circuit.
2012-10-09
VPH_PWR does not output power. The MAX8903 is a charging chip in DC-DC
mode. If it does not output power, probably the chip body or certain inductors are
abnormal.
The battery cannot be charged. This fault is attributable to the following factors:
(1) Software fault. If CEN is not active, the MAX8903 chip cannot start the
charging mode.
(2) Battery fault. The NTC resistance is abnormal.
(3) The resistor mapping to the charging current of the IDC pin is abnormal.
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