CAN bus LED controller for automotive lighting

“With 32 regulated current sources, independently programmable from 1mA to 15mA, L99LDLH32 can drive individual pixels in external and interior lighting applications. Global dimming is also provided, with 8-bit resolution,” according to the company, whose data sheet said that it is particularly aimed at external rear lighting.

Outputs regulate on the high-side, allowing common cathode LED or OLED arrays to be used. To cover emitter forward-voltage spread, up to 35V can be applied to the Vpre-reg to power the LED current sources. The device’s internal circuits require 5.5 to 28V (nominally a battery connection, 40V abs max) through another pin.

Vpre-reg and Vsupply are internally monitored by an 8bit ADC, and the results stored in a dedicated register. The ADC also monitors device temperature and all the output channels.

CAN FD Light protocol handler and transceiver are integrated for connection to the vehicle’s communication infrastructure and domain electronic control unit.

“Based on proven industry standards, CAN FD Light’s synchronised commander-responder communication, conceived for controlling simple devices like lights and sensors, saves external components such as timing crystals,” said ST. “Data bandwidth of 1Mbit/s enables designers to create complex animated light patterns and permits smoothly modulated transitions and dimming.”

On-chip memory allows programming of parameters including current level and PWM dimming for stand-alone operation – and an provide a fail-safe mode to cover communication loss.

As it is intended to be used with safety-critical lighting such as tail lights, stop lights and indicators, the device includes functional safety enhancers such as a fault status pin, programmable watchdog, short-circuit detection,  open-load detection and the voltage and temperature monitors mentioned above.

Frequency dithering is included to spread-out electromagnetic emissions.

Made on ST’s BCD9sL process, the IC is is AEC-Q100 qualified and comes in a 7 x 7mm QFN48 with wettable flanks and an exposed thermal pad.

The L99LDLH32 product page can be found here and the data sheet is here.

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