Huawei Y511-U030 Repair Manual page 39

XXXX The basic version Repair Manual
Abnormal shutdown refers to the battery voltage is too low, the chip temperature is too high,
DCDC1 or LDOD1 under the pressure caused by the shutdown. Abnormal shutdown is
automatically completed by the chip. Each boot, the software can read register SHDN_STATUS to
view the cause of the last shutdown. See timing diagram of switch machine shutdown sequence.
After the shutdown except for the PMU internal power supply LDO work, other power is off. In the
off state, the control module switch machine is in working state, when the starting conditions, start
the boot process.

PMU VSB end of the external battery backup, after the shutdown even pull the lithium
battery, RTC still count on a date and time, before the shutdown calibration of RTC after
shutdown is still valid;
Power on chip, a baseband chip inside ROM BOOT program from the start address operation,
and corresponding driver initialization, storage equipment, began to access the external SDRAM
and NAND FLASH, the code is stored in the NAND FLASH read into SDRAM began operation,
system of video, audio, radio and other devices one by one start, finish the boot process.

No boot failure analysis process flow:
Divided into specific press the power button does not switch on the mobile phone, charger
does not boot, large current does not boot, crashes, slow response to fault the software does not
boot.
一.
PCBA does not boot repair analysis.
Use an external power supply, it is best to have the output current and output voltage, and
current protection, in short, will automatically cut off the output current, so that the mobile phone
does not have more damage, adjusting supply voltage is 4.0V, output can supply current is
appropriate for the 1.0A. For the power PCBA, current situation observation stable:
1.
The current is too small 10MA, common main clock does not work, check the main clock
X301, the main chip U101, U301 power management chip, memory (U402), and peripheral
devices have no weld, even tin, whether the normal power supply. The inspection focused on the
26MHz clock output amplitude is normal, if the waveform distortion, frequency stability. It will also
examine the input and output amplitude slow clock 32.768K is normal, if the waveform distortion,
frequency is stable, if not normal to the related circuit check whether RTC, weld, backup battery is
charging, peripheral resistance is normal.
2. Current basic normal 30mA, common software is bad, can be re download the program
test. If the current continued to stay in the 30mA or higher than a value of about 30mA and does
not change, is likely to be the baseband chip weld loose or damaged.
3. Current hundreds of Ma phenomenon, cause current protection, focus on examination and
VBAT connection device, respectively, check the power supply with a multimeter (VBAT) on the
existence of short circuit phenomenon and VCHARGE on, if there is a short circuit phenomenon,
please check the ESD protection devices are breakdown, and whether there is damage or short
circuit phenomenon on some devices related to the VBAT network, the principle is from easy to
difficult, to exclude some easy to judge the part of.
2013-09-25
V1.0
华为机密，未经许可不得扩散
internal public
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