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iPhone audio circuit repairing

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This video mainly explains the working principle of iPhone audio power amplifier

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The working principle of the audio power amplifier of iPhone8 to iPhoneX models is the same

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Audio power amplifiers are divided into earpiece power amplifiers and speaker power amplifiers in real objects

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The two chip models are the same, the principle is the same,

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and the maintenance methods are also the same.

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There is only one signal difference between them in the block diagram

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The speaker amplifier does not have a PDM bus, and the PDM bus is the handset data bus

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The first step of the working principle of the audio power amplifier,

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when the battery or adjustable power supply is connected,

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the charging tube will convert and generate the main power supply,

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one way will provide the working voltage for the audio power amplifier,

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and the other way will be connected to the inductor to prepare for the boost of the audio power amplifier

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Step 2, after triggering the boot,

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the main power supply will output more than 30 power supplies,

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of which 1.8V power supply will provide the working voltage for the audio amplifier again

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Step 3, after the CPU working condition is normal,

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it will read and detect the audio power amplifier through the I2C bus

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Step 4, when starting to the audio circuit,

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the big audio will send a clock signal for the audio power amplifier

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Step 5, when starting to the audio circuit,

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the CPU is sending a reset signal for the audio amplifier

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Step 6, after the audio power amplifier works normally,

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it will send an interrupt signal to notify the CPU

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Step 7, when using the voice function,

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the big audio will send the audio data to the audio amplifier through the I2S bus

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Step 8, after the audio power amplifier receives the sound data,

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the internal boost module starts to work and boosts the main power supply of PP_VDD_MAIN to about 8V

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Step 9, after the audio power amplifier is boosted,

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it will be converted by the internal module,

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and then output the positive and negative signals of the speaker

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The speaker produces sound after receiving positive and negative voltages,

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then our ears can hear the sound from the speaker

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In the functional block diagram, PDM is the audio data bus to the earpiece power amplifier

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After the earpiece amplifier recognizes the audio data sent by the PDM bus,

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it will not generate a boost

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It will output audio data directly through the internal module

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At this time, the audio data has not been boosted, the voltage is relatively low,

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and the sound from the earpiece speaker will be relatively small

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These signals are audio power amplifier operating conditions

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If one of them is abnormal, there will be no earpiece,

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or no sound from the speaker at the bottom,

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we need to find the corresponding line during maintenance

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That's all for this video