The LT4276BIUFD#PBF is an LTPoE++/PoE+/PoE powered device (PD) forward/flyback controller in 28 pin QFN package. This device is a pin to pin compatible family of IEEE 802.3 and LTPoE++ powered device (PD) controllers. It includes an isolated switching regulator controller capable of synchronous operation in both forward and flyback topologies with auxiliary power support. The LT4276B is a fully 802.3at compliant (25.5W type 2 (PoE+) PD) and no opto isolator required for flyback operation. The device supports both forward and flyback power supply topologies and can be configurable for a wide range of PoE applications. Auxiliary input voltage can be accurately sensed with a resistor divider connected to AUX pin. The LT4276B utilizes an external, low RDS (ON) N channel MOSFET for hot swap function which maximizes power delivery, efficiency, reduces heat dissipation and eases thermal design.
IEEE 802.3at/af compliant
Superior surge protection (100V absolute maximum)
Auxiliary power support as low as 9V
Maximum PD (powered device) power of 25.5W
External hot swap N channel MOSFET for lowest power dissipation and highest system efficiency
Greater than 94% end to end efficiency with LT4321 ideal bridge
Vin operating voltage is 60V (VPORT, HSSRC)
Switching frequency of 300KHz at ROSC = 45.3Kohm to GND
Maximum PG duty cycle is 66%
Operating junction temperature range from -40°C to 85°C
(EN)
