ST1S31 is a 3A DC step-down switching regulator from ST. It adopts internally compensated 1.5MHz fixed-frequency PWM synchronous step-down circuit, with input voltage range of 2.8V~5.5V and output voltage adjustable range of 0.8V~VIN. It has a 60mΩ high-side switch and a 45mΩ synchronous rectifier, which can achieve high efficiency and low output voltage.