The LT®3990 is an adjustable frequency monolithic buck switching regulator that accepts a wide input voltage range up to 60V, and consumes only 2.5μA of quiescent current. A high effi ciency switch is included on the die along with the catch diode, boost diode, and the necessary oscillator, control and logic circuitry. Low ripple Burst Mode operation maintains high effi ciency at low output currents while keeping the output ripple below 5mV in a typical application. Current mode topology is used for fast transient response and good loop stability. A catch diode current limit provides protection against shorted outputs and overvoltage conditions. An enable pin with accurate threshold is available, producing a low shutdown current of 0.7μA. A power good fl ag signals when VOUT reaches 90% of the programmed output voltage. The LT3990 is available in small 10-pin MSOP and 3mm × 2mm DFN packages.