iPhone trigger circuit

In this lesson, we will mainly analyze the trigger circuit in the circuit diagram

Take the iPhone XS model as an example

In the circuit diagram,

as long as the main power supply receives the main power supply,

it will generate standby power supply PP1V8_ALWAYS

Now let's look for the standby power supply in the circuit diagram

We open the iPhone XS circuit diagram, component map and bitmap

Search PP1V8_ALWAYS directly in the circuit diagram

According to the circuit diagram,

we know that the power supply is output by the main power supply,

so we need to find the main power supply when we search

The U2700 is the main power supply

If you don't know, you can look at the component map,

U2700, which corresponds to the main power supply

This power supply we can view in the bitmap

After the power supply is output,

it does not provide operating voltage for other components

After the standby power supply search is completed,

let's look for the switch signal from the switch pin to the main power supply

and the switch signal from the main power supply to the CPU

First, open the component map and locate the switch seat

According to the position number of the switch seat,

we will search the switch position number in the drawing

Locate the switch position number,

according to the seat pin English identifier

the iPhone 7- XSMax switch identifier is BUTTON_POWER_KEY

The second pin in the circuit diagram is the switch pin,

and the switch pin signal will be directly connected to the main power supply

Let's see if it goes through other components in the drawing

In the drawing we search for the switch pin

After searching, we can see that the switch pin signal is connected to DZ4310,

which is an anti-static diode and plays a protective role

It is connected to the resistor R4310,

which belongs to the protection resistor

After passing the resistor it is connected to a capacitor C4310

We search for the English name after the resistor

In the search process, the same name means the same signal

The name of the signal is the same, on behalf of the boot signal

The power-on signal is connected to pin J14 of the U2700,

which refers to the main power supply

According to the circuit diagram,

after the switch pin signal reaches the main power supply,

the main power supply converts the switch signal to the CPU

The conversion circuit is at the point

where the switch pin signal reaches the power supply

The switch pin connected to the power supply is BUTTON2

This identifier is PMU_TO_AP_BUTTON_POWER_KEY

This is the switch signal from the main power to the CPU

We can view the connection through the dots

This signal is directly connected from the main power supply to the CPU

We can look for signals in the same way for iPhone 7 and older models

So that's it for this lesson