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iPhone touch circuit repairing

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This video mainly explains the working principle of iPhone X, XS, XSMax touch circuit

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The working principles of these three models are basically the same,

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but the individual detection signals are slightly different

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The first step of the working principle, after we trigger the switch,

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the main power supply will output more than 30 channels of power supplies

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Among them, the 1.8V_TOUCH power supply will first provide the working voltage

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for the touch screen

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Step 2, after the main power supply outputs the power supply,

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it will send a 32KHz clock signal to the touch screen

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Step 3, when the CPU working condition is normal,

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it will read the data in the screen data storage chip on the touch cable through the I2C bus

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Step 4, the CPU self-test is completed,

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and the power supply will send 1.1V power supply to the touch screen during system startup

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Step 5, when starting to the touch circuit,

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the touch power supply sends negative 6.7V power supply,

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10V power supply and 3.5V power supply to the touch screen

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Step 6, when starting to the touch circuit,

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the CPU sends a reset signal for the touch screen

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Step 7, after the power supply, clock signal and reset signal of the touch screen are normal,

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the CPU will read and detect the touch screen through the SPI bus

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Step 8, after the touch screen is detected,

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it will send a 5.25V turn-on signal for the touch power supply

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Step 9, after the touch power supply receives the turn-on signal,

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it will send a 5.25V core power supply to the touch screen

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Step 10, after the power supply, clock and reset signals of the CPU are normal,

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then the touch screen can work normally

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The touch screen will send an interrupt signal to notify the CPU

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Step 11, after the CPU receives the interrupt signal,

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it will receive the touch data through the SPI bus

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After the CPU receives the touch data,

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it will execute the corresponding commands

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These signals are the main working conditions when the touch screen works

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In the functional block diagram,

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other green lines are other detection signals of the touch screen

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AMUX is the monitoring signal sent to the main power supply after the touch screen works normally

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The main power supply uses this signal to identify whether the touch screen is normal

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ORB_SCAN is the detection scan signal from the touch power supply to the touch screen

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When working normally, the touch power supply will check

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whether the touch screen is working normally from time to time

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In case of abnormality, it will turn off the power supply of the touch screen

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SWD is the serial debug bus,

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the CPU will send test data from this bus to detect the touch screen

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The UART bus is an asynchronous transceiver bus

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It is mainly used to transmit data when the touch screen is used for other circuits, such as 3D touch

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REF_CLK is the reference clock sent by the CPU to the touch screen

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The clock signal is 24MHz, which is mainly used to transmit other signal data

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BSYNC is a synchronous signal sent by the CPU to the touch screen

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AOP_IRQ is Hall interrupt signal

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For example, when making a phone call, when an object approaches,

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the sensing distance will turn off the touch screen

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The CPU will send an interrupt signal to notify the touch screen

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In the functional block diagram, these signals are the main working signals of the touch screen

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There is an abnormal signal, which may cause the touch screen to not work

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When we overhaul, first overhaul the main working signals of the touch screen

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If there is no problem with the main signals, then measure other detection signals

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Ok, that's all for this video