LTC4271

FEATURES nn 12 Independent PSE Channels nn Compliant with IEEE 802.3at Type 1 and 2 nn Chipset Provides Electrical Isolation nn Reduced BOM Cost nn Eliminates up to 6 High Speed Opto-Couplers nn Eliminates Isolated 3.3V Power Supply nn Low Power Dissipation nn 0.25Ω Sense Resistance Per Channel nn Very High Reliability 4-Point PD Detection nn 2-Point Forced Voltage nn 2-Point Forced Current nn VEE and VPORT Monitoring nn 1 Second Rolling IPORT Averaging nn Supports 2-Pair and 4-Pair Output Power nn 1MHz I2C Compatible Serial Control Interface nn Available In Three Power Grades nn A-Grade – LTPoE++™ 38.7W to 90W nn B-Grade – PoE+ 25.5W nn C-Grade – PoE 13W nn Available In 52-Lead 7mm × 8mm (LTC4270) and 24‑Lead 4mm × 4mm (LTC4271) QFN Packages APPLICATIONS nn PoE PSE Switches/Routers nn PoE PSE Midspans LTC4270/LTC4271 12-Port PoE/PoE+/LTPoE++ PSE Controller DESCRIPTION The LTC®4270/LTC4271 chipset is a 12-port power sourcing equipment (PSE) controller designed for use in IEEE 802.3at Type 1 and Type 2 (high power) compliant Power over Ethernet (PoE) systems. Transformer-isolated communication protocol replaces expensive opto-couplers and complex isolated 3.3V supply resulting in significant BOM cost savings. The LTC4270/LTC4271 chipset delivers lowest-in-industry heat dissipation by utilizing low-RDS(ON) external MOSFETs and 0.25Ω sense resistors. Advanced power management features include per-port 12‑bit current monitoring ADCs, DAC-programmable current limit, and versatile...