Li Auto L9 Headlight Driver Board Teardown

Today we are disassembling a Li Auto L9 headlight driver board. Inside, there is a single PCB. Let's take a closer look at the specific components on it.

Infineon 32-bit automotive-grade microcontroller CYT2B75BADQ0A, based on the Arm Cortex-M4F core, with a maximum main frequency of 160 MHz, integrating a DSP instruction set with a floating-point unit. In lighting applications, it not only processes commands from the vehicle's CAN/LIN buses in real time but also drives high-side switches, collects current feedback signals, and executes PID closed-loop algorithms to ensure independent dimming accuracy for multiple LED channels. In addition, this MCU achieves **ASIL-B** functional safety level and complies with the ISO 26262 standard, providing fundamental reliability for headlamp operation in autonomous or assisted driving scenarios.

Texas Instruments dual-channel synchronous buck LED driver TPS92520-Q1 (5 pieces), each channel capable of delivering up to 1.6 A of current. Its operating input voltage ranges from 4.5 V to 65 V, making it perfectly adaptable to transient overvoltage and cold-crank conditions in automotive 12 V/24 V electrical systems.

For stepper motor control at the execution level, the Li Auto L9 uses Texas Instruments automotive-grade dual H-bridge stepper motor driver DRV8899-Q1, supporting an operating voltage from 4.5 V to 37 V and a drive capability of up to 1.5 A per bridge (maximum). The automatic leveling motor, adaptive steering motor, and lens switching shutter inside the headlamp all require precise position control from stepper motors. The DRV8899-Q1 features a built-in microstepping indexer and current regulation function, supporting up to 1/32 microstepping for smooth and ultra-low-noise motor operation. Its integrated open-load detection, overcurrent protection, and thermal shutdown mechanisms simplify external circuit protection design and meet AEC-Q100 qualification.

Infineon N-channel automotive-grade MOSFET, model IAUC60N10S5L110;

Panjit automotive-grade Schottky barrier rectifier diode, model MBR8H120PC;

Nexperia automotive-grade NPN power bipolar transistor, model PHPT61003NY;

Infineon automotive-grade system basis chip (SBC), model TLE9261. This SBC integrates a low-dropout (LDO) linear regulator, a high-speed CAN transceiver, a watchdog timer, and multiple high-side and low-side switch outputs. It supplies a stable 5V power to the MCU while directly communicating with the vehicle's CAN bus to receive lighting control commands and return diagnostic information. The TLE9261's built-in fault management and wake-up logic maintains extremely low quiescent current when the vehicle is in sleep mode, meeting modern smart vehicle energy consumption regulations. Its MCU-independent protection mechanisms, such as under-voltage reset and over-temperature shutdown, add redundant reliability to the entire driver board.