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In this lesson, we talk about the framework of the startup operation process,

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that is, the structure of the startup operation process

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The first thing to work in a mobile phone is the battery

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Shown here is the battery holder

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The battery mainly provides a power supply, VBAT, or VBATT

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Android phones generally have these two codes

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The power supply reaches the charging chip,

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and the charging chip controls the MOS tube to work,

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so that the MOS tube is turned on, generating a main power supply

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This main power supply has two codes on the mobile phone,

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VPH_PWR and VBT_SYS

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In Android phones,

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this MOS tube is usually integrated in the charging chip,

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so we draw a dotted line here

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What is the main work of the charging chip?

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It mainly controls the internal MOS tube,

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and turns the power supply of the positive electrode of the battery into the main power supply,

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VPH_PWR,

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its voltage is equal to the voltage of the battery generally

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After the main power supply is generated,

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it needs to supply power to the power chip

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The power chip is also called the power management unit,

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abbreviated as PMU

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The internal standby circuit of the power chip works,

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provides voltage to the crystal oscillator,

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and the crystal oscillator works in standby

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At this time,  

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the power chip will give a voltage of 1.8V to the power-on signal line,

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usually through a series resistors, and then to the power-on button

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The power-on signal lines on the Android phones are called PWRON, or KYPD_PWR

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These two types of codes are more used

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This is the boot seat,

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which is the connection seat of the power-on signal,

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and the cable with the power-on button installed on the boot seat

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When we want to pull down this signal,

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we usually connect the power button signal to the ground wire

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The symbol of the ground wire in the circuit is like this

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We press the power button to connect the signal to the ground wire,

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usually for more than 5 seconds

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After 5 seconds,

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the trigger circuit inside the power supply detects the change of this signal,

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and it will output power

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Okay, that's it for this lesson