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The maintenance of iPhone startup constant current and current jump faults

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In this video, we mainly explain the working principle of constant current and current jump

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Let's look at the main power supply first

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In the first step, when we buckle the battery or connect the adjustable power supply,

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the main power supply will be generated

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The second step, after the main power supply has the main power supply,

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it will provide the working voltage for the 32.768M crystal oscillator

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After the crystal oscillator has power supply,

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it will generate a 32.768M clock signal and return to the main power supply

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This clock signal is a necessary condition for the main power supply to output other signals

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If the 32.768M crystal oscillator is damaged,

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it will cause the working conditions of the main power supply to be unsatisfied

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Therefore, if the crystal oscillator is damaged, it will also cause a constant current

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In the third step, after the main power supply receives the main power supply,

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it will generate PP1V8_ALWAYS standby power supply

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This power supply will provide a pull-up voltage for the switch pin internally through the power supply IC

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Step 4, when we trigger the switch,

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the voltage of the switch pin will change from 1.8V to 0V

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This is the power on signal, it will be sent to the main power supply

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After the main power supply receives the power-on signal,

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it will wake up the CPU and start working

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At the same time,

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the power supply module inside the power supply will generate about 30 channels of power supplies

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to provide working voltage for other chips in the mainboard

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With so many chips, the CPU will work first

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In order for the CPU to work, in addition to power supply,

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it also needs a clock signal and a reset signal

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After the CPU has power supply,

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the internal clock module starts to work,

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and it will generate a power supply to provide working voltage for the 24M crystal oscillator

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After the 24M crystal oscillator has power supply,

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it generates 24M frequency,

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and then returns to the inside of the CPU to send clock signals for other chips managed by the CPU

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After the clock module works normally,

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it will output a test clock signal to the main power supply to notify the main power supply

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After the main power supply receives the test clock signal, it will send a reset signal to the CPU

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After the CPU has power supply, clock signal and reset signal,

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the internal self-test module will work

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Ok, that's it for this lesson