LED Driver, Synchronous Boost and Series / Parallel

The FAN5776 is a synchronous, constant-current LED driver capable of efficiently driving up to ten LEDs in a five-string, two-series LEDs per string configuration. Optimized for small form-factor applications, the 1.8 MHz switching frequency allows the use of tiny chip inductors and capacitors. For safety, the device features integrated over-voltage, short-circuit, and thermal shutdown protections. In addition, input under-voltage lockout protection is triggered if the battery voltage is too low. The FAN5776 is comprised of low-dropout, high-side current sources, enabling a high efficiency delivery of power from the battery to the LEDs. The LED current control is established with a series RSET resistor, which is connected between the internal voltage reference on the chip and ground. During operation, FAN5776 holds the boost regulator’s voltage on COUT during the off cycle of the PWM dimming, which helps minimize audible noise.