100V Ideal diode bridge controller for PoE powered applications

The LM74681 is a 100V ideal diode bridge

controller capable of driving a MOSFET bridge, enabling efficient low-loss bridge

rectifier solutions in Power over Ethernet (PoE) applications. It allows a Power over

Ethernet, powered device (PD) to receive power from RJ-45 data pairs, spare pairs, or

any combination of the two, regardless of voltage polarity. The integrated charge pump

allows use of N-channel MOSFETs, which are smaller and more cost effective than

P-channel MOSFETs for the same power level. The LM74681 along with N-channel MOSFET

bridge can replace the conventional diode bridge and can be conveniently implemented in

both 2-pair and 4-pair PoE PD systems. In the event of a power source failure or short

circuit, a rapid turn-off feature reduces reverse current spikes. The device also

features an ultra-low quiescent current of 0.27µA, which ensures that there is no data

corruption during the PoE PD detection and classification phase. This device is

characterized for operation over a junction temperature range of –40°C to +125°C.