The LM5071 pulse-width modulation (PWM) controller can accept power from a Power-over-Ethernet (PoE) IEEE 802.3af Ethernet cable. This single-chip device from National Semiconductor also can accept power from external ac adapters. Designers can use it to create PoE powered devices (PDs) that can handle power from either source.
Voice over Internet Protocol (VoIP) phones, Wi-Fi hotspots, and Ethernet security cameras that include the chip all can work anywhere in the Ethernet network. If the CAT5 cable is PoE-powered, then everything is well and good. If not, designers can plug in a wall-wart. Either way, the LM5071 can handle the job.
On the ac-adapter side, the chip can manage a maximum input voltage of 80 V. It also provides up to 1 MHz of user-programmable oscillator frequency and overtemperature protection, plus a voltage reference and a high-performance error amplifier for non-isolated applications. It's available with 50% or 80% maximum PWM duty cycle to support a variety of dcdc converter topologies.
Available in lead-free and standard small-footprint TSSOP-16 packages, it costs $1.45 each in 1000-unit lots.