Description

This reference design shows how to use pulse width modulation (PWM) to dim an automotive headlight or tail light with precision of better than 2% duty cycle without the necessity of using a microcontroller. This allows the design to be cost competitive. Devices used in this design are the TPS92691-Q1 multi-topology LED driver in boost and boost to battery configuration controlling the LEDs.  TLC555-Q1 LinCMOS timer: together with OPA2377-Q1 operational amplifier: measure and generate an accurate PWM signal by applying a feedback loop and a precision shunt regulator for setting the duty cycle accurately. The design's input stage is EMI/EMC filtered and can be directly supplied by the car's battery.