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    89. Working principle of trigger circuit 2
    n this lesson, we will mainly explain the working principle of the trigger circuit of iPhone 6 to iPhone 6SP, and how to identify signals in the circuit diagram
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    iPhone trigger circuit

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    In this lesson, we will mainly explain the working principle

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    of the trigger circuit of iPhone 6 to iPhone 6SP,

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    and how to identify signals in the circuit diagram

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    In order for a main power supply to work,

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    it must first have a main power supply

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    This power supply is what we talked about in the previous lesson

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    In the schematic diagram, we can look for the signal,

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    just look for the standby power supply PP1V8_ALWAYS,

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    switch pin to the CPU and power line

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    Let's take the iPhone 6 as an example

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    and look at its standby power supply and the pin to power line

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    First of all, we open the component map, circuit diagram and bitmap of the iPhone 6

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    In the last video, we talked about that

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    the Apple's entire line of standby power is labeled PP1V8_ALWAYS

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    We simply type the name into the bitmap to find the standby power supply

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    We go to the search box, select the search signal,

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    type PP1V8_ALWAYS, and click Search

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    In the bitmap, we can see that this power supply is generated by the power supply IC,

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    one way to the CPU,

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    the other way through a resistor to supply power to the switch pins

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    The switch pin connects the CPU to the main power supply

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    and also connects a pull-up resistor

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    Now let's look it up

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    First, locate the switch connector in the component map,

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    and then search for the switch connector in the circuit diagram

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    After the switch socket is searched,

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    the English identifier of the iPhone 6 switch socket is BUTTON_HOLD_KEY,

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    according to its English abbreviation

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    In this seat, the second pin is the boot pin

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    In the circuit diagram, the switch pin will reach the power supply and CPU

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    After searching the circuit diagram for the name of the switch,

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    this signal is first connected to an inductor FL0809,

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    next to which an antistatic diode is connected

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    After passing the inductor, it will connect a capacitor C0810

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    After passing through the inductor, where does the signal connect to?

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    We need to search for the signal behind the inductor

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    After a search, we find that the signal is connected to a resistor, R0314

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    This resistor is connected to PP1V8_ALWAYS at one end

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    and a switch signal at the other

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    This resistor is the pull-up resistor

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    This signal is also connected to a chip, the U0201,

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    which is actually the CPU

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    This signal is also connected to the power IC

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    Let's look at number three in the search list

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    This signal comes in and is connected to the chip U1202,

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    which is the main power supply

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    In this way, we according to the circuit diagram,

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    the switch pin signals connected to the components are found

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    Ok, that's it for this lesson

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