ADP1621 DC-to-DC Controller Analog Devices ADP1621 DC-to-DC Controller is offered as a fixed-frequency, pulse-width modulation (PWM), current-mode, step-up converter controller with a 92% efficiency rating and ±1% initial accuracy. The ADP1621 Controller drives an external N-channel MOSFET to convert the input voltage to a higher output voltage. The device uses lossless current sensing for switch-node voltage <,30V and resistor current sensing for switch-node voltage >,30V. Designers can use the ADP1621 Controller to drive SEPIC, flyback, and forward converter topologies.