The ISL9440, ISL9440A and ISL9441 are quad-output synchronous buck controllers that integrate 3 PWM controllers and 1 low drop-out linear regulator controller, which are full featured and designed to provide multi-rail power for use in products such as cable and satellite set-top boxes, VoIP gateways, cable modems, and other home connectivity products as well as a variety of industrial and general purpose applications. Each output is adjustable down to 0.8V. The PWMs are synchronized at 180 out of phase thus reducing the RMS input current and ripple voltage. The ISL9440, ISL9440A and ISL9441 offer internal soft-start, independent enable inputs for ease of supply rail sequencing, and integrated UV/OV/OC/OT protections in a space conscious 5mmx5mm QFN package. The ISL9440 and ISL9440A offer an early warning function to output a logic signal to warn the system to back up data when input voltage falls below a certain level. The ISL9440, ISL9440A and ISL9441 utilize internal loop compensation to keep minimum peripheral components for compact design and a low total solution cost. These devices are implemented with current mode control with feed forward to cover various applications even with fixed internal compensations.