LTC1778-1

U U LTC1778/LTC1778-1 Wide Operating Range, No RSENSETM Step-Down Controller FEATURES ■ No Sense Resistor Required ■ True Current Mode Control ■ Optimized for High Step-Down Ratios ■ tON(MIN) ≤ 100ns ■ Extremely Fast Transient Response ■ Stable with Ceramic COUT ■ Dual N-Channel MOSFET Synchronous Drive ■ Power Good Output Voltage Monitor (LTC1778) ■ Adjustable On-Time (LTC1778-1) ■ Wide VIN Range: 4V to 36V ■ ±1% 0.8V Voltage Reference ■ Adjustable Current Limit ■ Adjustable Switching Frequency ■ Programmable Soft-Start ■ Output Overvoltage Protection ■ Optional Short-Circuit Shutdown Timer ■ Micropower Shutdown: IQ < 30µA ■ Available in a 16-Pin Narrow SSOP Package U APPLICATIO S ■ Notebook and Palmtop Computers ■ Distributed Power Systems DESCRIPTIO The LTC®1778 is a synchronous step-down switching regulator controller optimized for CPU power. The controller uses a valley current control architecture to deliver very low duty cycles with excellent transient response without requiring a sense resistor. Operating frequency is selected by an external resistor and is compensated for variations in VIN. Discontinuous mode operation provides high efficiency operation at light loads. A forced continuous control pin reduces noise and RF interference, and can assist secondary winding regulation by disabling discontinuous operation when the main output is lightly loaded. Fault protection is provided by internal foldback current limiting, an output overvoltage comparator and option...