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ASUS
L3 Service Manual
1)power supply IC to work properly, must have a working voltage, the voltage is generally the battery
voltage or external power supply voltage.
2) boot trigger signal added to the power supply IC, press the power button, the trigger signal to start
the level of change.
3) Power supply IC is generally integrated with multiple groups of controlled and uncontrolled voltage
regulator circuit, when there is a trigger signal, the power supply IC regulator output should be voltage
output.
4) Have the power on hold signal (watchdog signal). Power-on maintenance signal from the CPU, power
IC only to get the power to maintain the signal to continue after the output voltage.
Use the external power supply, it is best to have the output current and output
voltage display, and there is current protection, encounter short circuit case, will
automatically cut off the output current, the phone will not have greater damage,
adjust the power supply voltage of 4.0 V, the output can supply current of 2.0A is
appropriate. To PCBA power on the boot, pay attention to the battery near the
connector pin to connect the 10K to the ground resistance to simulate the battery in
place. Otherwise it can not boot
Use the external power supply, it is best to have the output current and output
voltage display, and there is current protection, encounter short circuit case, will
automatically cut off the output current, so that the phone will not have greater
damage, adjust the power supply voltage of 4.0 V, the output can supply current of
2.0A is appropriate. Through the fake battery to the PCBA power test.
1）Power on the first press the power button to observe the shutdown leakage
current, if the leakage current is very large, focus on checking with VBAT connected
devices, with a multimeter to check the power supply (VBAT) to ground and VBUS to
ground whether there is a short circuit,
Short circuit phenomenon, please first
check whether the relevant ESD protection device is punctured, and then on the VBAT
network related to some of the devices are damaged or short circuit phenomenon, the
principle is the first easy, first to exclude some easy to judge the part.
2. current boot is too small after about 10MA, the common main clock does not work, check the 19.2M
X0501 clock oscillator, U1500 chip, power management chip U0501 and U0401, and peripheral devices
have no weld, even tin, power supply is normal.
3）Press the power button after the basic current 100 ~ 200mA up and down, common
software is bad, you can re-download the program test.
Such as troubleshooting
software problems can not be downloaded, it is likely that the main chip U1500 or
memory U1501 Welded loose or damaged
4）Press the power button after the current is very large, hundreds of milliampere
phenomenon, causing current protection, focusing on power supply timing diagram,
Check the power output to the ground whether there is a short circuit phenomenon, if
there is a short circuit, followed by the power of the device.
2017-06-08
ZD553KL
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