Typical Application Circuit for LTC1539CGW High Efficiency Low Noise 5V/20mA Standby, 5V/3A, 3.3V/3.5A and 12V/200mA Step-Down Converter. The LTC1539 is a multi outputs synchronous step-down switching regulator controller which drives externa N-channel power MOSFETs in a phase-lockable fixed frequency architecture