The ADP1621 Controller operates using a 2.9V-5.5V IC supply input voltage. Higher input voltages (>5.5V) are achievable with the use of a small signal NPN pass transistor or a single resistor. The device allows a power input voltage as low as 1V for fuel cell applications. Designers can use an external resistor to set the switching frequency over a 100kHz-1.5MHz range. The SDSN pin synchronizes the switching frequency to an external clock. ADP1621's input supply current is less than 3mA during normal operation and less than 10μA during the shutdown. The design of the ADP1621 Controller allows the device to drive large external MOSFETs and support load currents above 10A.