This reference design is a dual string LED driver that implements an operational amplifier based circuit which balances the current in two LED rings. The operational amplifier circuit senses current in a reference string and uses feedback from a mirrored string to bias a MOSFET that egulates the current between the strings.
The design uses the TPS92692-Q1 multi-topology LED driver in a boost configuration to drive the LEDs. The TPS92692-Q1 features spread spectrum frequency modulation for EMI performance, analogue current adjustment and internal PWM dimming. This design includes adjustable linear thermal foldback using the LMT87-Q1 analogue temperature sensor, as well as current limiting, in the event the mirrored string fails open circuit. The design also features two brightness modes. One mode is a full brightness mode ('DRL') and the other is a PWM dimming mode ('Position') which reduces brightness.