Figure 9-9 Charging Management Circuit Diagram 4 - Huawei U8815 Maintenance Manual

U8815
Maintenance Manual

Figure 9-9 Charging management circuit diagram 4

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Figure 9-10 shows the troubleshooting process for charging failures.
Issue 1.0 (2012-02-13)
Analysis
U8815 adopts the PM8029 circuit management chip and integrates a charging scheme.
Three charging states are supported: trickle charging, constant current charging, and
constant voltage charging. All the preceding charging methods use the same charging
channel: VEXT_DC -> VCHG -> VPH_PWR -> Q201, pin3 -> VBAT.
U8815 adopts the dedicated FAN5402UCX power supply chip for 1 A charging, and uses
I2C interfaces for communication and control: GPIO13 (I2C_SCL_DCDC) and GPIO13
(I2C_SCL_DCDC). The charging management chip obtains power from the VCHAG of
the USB port. The chip is controlled by the I2C. The output VPH_PWR supplies power
to the power management chip and the battery.
This chip supports three modes: charging mode, boost mode, and high resistance mode.
The charging mode is normal charging process. The boost mode is USB-OTG mode. The
high resistance mode is power-saving mode (standby mode) without charging.
Troubleshooting Process
There are two types of common charging failures:
− The phone has no response after a charger is connected to it.
− The phone displays an animated icon indicating that it is charging, but actually, the
battery is not charged.
− To troubleshoot charging failure, firstly check whether the battery connector is
damaged.
No charging indicator is displayed after the charger is connected to the phone.
A charging indicator is displayed after the charger is connected to the phone but the
phone cannot be charged.
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9 Principles and Failure Analysis
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