The LT4276AIUFD#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++ PD controllers. It includes an isolated switching regulator controller capable of synchronous operation in both forward and flyback topologies with auxiliary power support. The LT4276A employs LTPoE++ classification scheme and receives 38.7W, 52.7W, 70W or 90W of power at PD from RJ45 connector. It is backward compatible with IEEE 802.3 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 LT4276A 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.
- Supports LTPoE++ 38.7W, 52.7W, 70W and 90W, IEEE 802.3at 25.5W and IEEE 802.3af up to 13W standards
- Superior surge protection (100V absolute maximum)
- Auxiliary power support as low as 9V
- Maximum PD (powered device) power of 90W
- 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
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