MP3309L

The MP3309L is a WLED step-up converter for 2.7V-to-5.5V input that uses peak-current mode to regulate the LED current sensed through an external, low-side resistor. The 200mV feedback voltage and synchronous rectification reduces power loss and reduces PCB space requirements. 
The MP3309L features a programmable switching frequency to optimize efficiency. It supports both analog and PWM dimming. 
In addition, the MP3309L has LED open protection, cycle-by-cycle current limit protection, thermal shutdown protection.