MP4657B

The MP4657B is a single-stage, flyback, 4-string LED driver and system voltage (V_SYS) 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 (V_IN), 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 (I_LED) 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 I_LED and V_SYS. If the PWM signal is effective, then the LED current loop is regulated via the flyback power stage, and V_SYS 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 V_SYS.

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.