This paper describes the MAX5953A — an IEEE 802.3af PD Interface and PWM Controllers with Integrated Power MOSFETs. It provides a simple and inexpensive, yet complete, nonisolated power solution for a powered device (PD) in a Power-over-Ethernet (PoE) system. The circuit provides the PD with detection and classification signatures in compliance with the IEEE 802.3af standard, plus programmable inrush-current control, an integrated power switch, a PWM controller, and integrated high- and low-side switches. The buck step-down converter is capable of > 80% conversion efficiency, while delivering 12V at 0.85A.