The ADP1864 is a compact, inexpensive, constant-frequency current-mode step-down DC-to-DC controller. The ADP1864 drives a P-channel MOSFET that regulates an output voltage as low as 0.8 V with 2% accuracy, for up to 5 A load currents, from input voltages as high as 14 V. The ADP1864 provides system flexibility by allowing accurate setting of the current limit with an external resistor, while the output voltage is easily adjustable using two external resistors. The ADP1864 includes an internal soft start to allow quick power-up while preventing input inrush current. Additional safety features include short-circuit protection, output overvoltage protection, and input under voltage protection. Current-mode control provides fast and stable load transient performance, while the 580 kHz operating frequency allows a small inductor to be used in the system. To further the life of a battery source, the controller turns on the external P-channel MOSFET 100% of the duty cycle in dropout.