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iPhone display circuit repairing

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This video mainly explains the working principle of the iPhone X display circuit

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Before learning the principle, let's first understand the characteristic of these three models

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From iPhone X to iPhone XS Max, these three models use OLED screens

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The flexible screen is characterized by self-illumination

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The display power supply is not installed on the mainboard, but on the screen cable

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So we can't find the display power supply in the mainboard

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In the picture, we can see that there is a chip on it,

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which is the display power chip

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Display circuit working principle

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Step 1, when the battery is buckled or the adjustable power supply is connected,

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the main power supply will be generated

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The main power supply will provide the working voltage for the display,

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mainly to provide power for the display power on the screen

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Step 2, when we trigger the switch,

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the main power supply will first send 1.8V power supply to the display screen after receiving the power-on signal

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And then sends 3V and 1V power supply to the display screen to provide it with working voltage

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Step 3, when booting to the display circuit, the CPU sends a reset signal for the display

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Step 4, after the display screen has power supply and reset signal,

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the display power supply on the screen starts to work to generate power supply for the display screen,

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after all the working conditions on the display screen are normal,

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it will send LIVE or WATCHDOG, and the ready signal will be sent to CPU

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Step 5, after the CPU receives the ready signal,

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it will send an interrupt signal to the display to notify the display that it is ready to receive display data

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Step 6, after the CPU sends the interrupt signal,

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it will send display data to the display screen through the MIPI bus,

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and the display screen will display the image at this time

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In the functional block diagram,

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ADCMUX is the signal for the main power supply monitoring the display power supply

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After the display power supply is working normally,

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it will send the ADCMUX signal to the main power supply

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PANICB or PANEL_ID signal is the main power supply

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to identify the abnormal detection signal for the display screen

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If there is a problem with this signal,

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it will cause the assembly screen to be displayed,

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but the original screen will not be displayed

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When troubleshooting no display failure,

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we need to measure all the working conditions of the display

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If one of the working conditions is abnormal,

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it will cause the screen to not display

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Ok, that's all for this video