The LM2655 is a current-mode controlled PWM step-down switching regulator. It has the unique ability to operate in synchronous or asynchronous mode. This gives the designer flexibility to choose between the high efficiency of synchronous operation, or the low solution cost of asynchronous operation. Along with flexibility, the LM2655 offers high power density with the small footprint of a TSSOP-16 package. High efficiency (>90%) is obtained through the use of an internal low ON-resistance (33m) MOSFET, and an external N-Channel MOSFET. This feature, together with its low quiescent current, makes the LM2655 an ideal fit in portable applications. Integrated in the LM2655 are all the power, control, and drive functions for asynchronous operation. In addition, a low-side driver output allows easy synchronous operation. The IC uses patented current sensing circuitry that eliminates the external current sensing resistor required by other current-mode DC-DC converters. A programmable soft-start feature limits start up current surges and provides a means of sequencing multiple power supplies.