Abstract: This reference design is for a highly efficient, flyback, 5V Class 3 powered device (PD) with a wide 9V to 57V auxiliary input. The design features the MAX5969B as its controller. The design also uses the MAX5974D, which controls current-mode PWM converters and provides frequency foldback for both the auxiliary input and power over Ethernet (PoE) applications. Using these devices, this reference design is IEEE® 802.3af/at compliant. It is also a high-performance, compact, and cost efficient solution for a Class 3 PD. The design can also support the wide auxiliary-input voltage range to provide 10W output power.