LC51A is thin DC-DC buck converter IC, containing temperature-compensated reference voltage source (1.25V), comparator, can effectively limit the current and control the duty cycle of the oscillator, driver and high current output switch, etc. outside with a small number of components can be composed of DC-DC step-down circuit. Compared with 34,063 products, can be achieved with a minimum of external components constitute a switching buck converter, widely used in car charger, DC buck converters and other products.