BMW Headlight Driver Board Teardown

From traditional halogen lamps and xenon lamps to today's LED matrix headlights, lighting technology is not only crucial for nighttime driving safety but has also become an important perception and execution unit for intelligent driving systems. As a representative of luxury car brands, BMW's LED headlight system is renowned in the industry for its "Angel Eyes" design language. In this edition, EEStop will disassemble a BMW front headlight driver board to explore the hardware solution inside.

Teardown

Through brute force disassembly, it was found that many integrated molded SMD inductors were directly attached to the housing. The thermal grease had solidified, likely due to age. The internal hardware solution is as follows:

Let's mainly look at the components on the PCB motherboard.

Infineon 32-bit microcontroller, model CYT2B95BACQ0AZEGS, mainly targeted at automotive systems such as body control units. It features an Arm Cortex-M4 CPU for main processing and an Arm Cortex M0+ CPU for peripheral and security processing. These devices contain embedded peripherals supporting CAN FD, LIN, and CXPI.

Infineon SBC chip, model TLE9471ES. This is a chip officially named Lite CAN SBC, integrating a CAN transceiver with multiple voltage regulators.

Infineon intelligent high-side switch, model BTS7200-2EPA. It integrates robust protection functions, including overload protection, short-circuit protection, overtemperature shutdown, and turn-off clamping for inductive loads. More importantly, it reports load status to the MCU via a current sense pin, diagnosing whether a filament is burned out or a line is short-circuited.

ON Semiconductor MOSFETs, models NVMFS5C673NLWF and NVMFS4C03NWFT1. The former is typically used for high-side switching or reverse battery protection. Given harsh conditions like load dump in automotive power supplies, the 60V withstand voltage provides ample margin. Its extremely low on-resistance minimizes conduction loss; the latter is typically used for low-side switching, speculated from the circuit to be for controlling a stepper motor driver.

Texas Instruments CAN transceiver, model TCAN1042-Q1. This is an independent high-speed CAN FD transceiver. Although the SBC integrates a transceiver internally, the product design still uses a separate chip, possibly to expand a second CAN bus for high-speed diagnostics or high-data-volume communication with other body domain controllers. It supports data rates up to 5Mbps and features excellent electromagnetic compatibility and bus fault protection.

Texas Instruments stepper motor driver, model DRV8889-Q1. Mainly used for adjusting headlight level or adaptive headlights, this is a 50V/1.5A bipolar stepper motor driver with integrated current sensing.

Now look at components on the other side of the PCB.

Texas Instruments LED driver, model TPS92520-Q1. This is the core component on the driver board. It uses peak current mode control to efficiently step down the vehicle's power supply to the forward voltage required by the LED chips. It supports fine current control via the SPI bus, enabling up to a 16:1 analog dimming range and extreme PWM dimming precision.

ON Semiconductor multiphase boost LED driver, model NCV78702MW0R2G. This multiphase boost LED driver is typically used for high-power front lighting modules.

The main component BOM for the BMW headlight driver board is as follows:

Summary

Through the disassembly of the BMW headlight driver board, it was found that its hardware solution basically consists of components from major international manufacturers. Regrettably, no Chinese chips were seen.