MP4657BGS

The MP4657B is a single-stage, flyback, 4-string LED driver and system voltage (VSYS) controller for LED backlighting on the secondary side. It controls the flyback power stage and an external N-channel MOSFET to regulate the system supply voltage and LED current loop with integrated 4-string LED current balancing. With a 4V to 16V input voltage (VIN), the MP4657B outputs a direct driving signal to control the N-channel MOSFET that regulates the system supply voltage. It also outputs a compensation signal to control the primary-side flyback (or other power stage) via an optocoupler. The device supports pulse-width modulation (PWM) dimming and analog dimming to the LED current (ILED) via the ADIMP/PWM pin. For analog dimming, apply a pulse signal with a >5kHz frequency to this pin. For PWM dimming, apply a pulse signal with a <5kHz frequency. The MP4657B uses an individual control method for ILED and VSYS. If the PWM signal is effective, then the LED current loop is regulated via the flyback power stage, and VSYS is further regulated by the N-channel MOSFET. Soft switching of the N-channel MOSFET reduces voltage spikes. If the PWM signal is ineffective, then the flyback power stage controls VSYS. Full protection features include LED open protection, LED short protection, LEDx pin short-to-ground protection, over-voltage protection (OVP), feedback (FB) open-loop protection, and thermal shutdown. The MP4657B is available in an SOIC-16 package.