Features

• 12 Independent PSE Channels
• Compliant with IEEE 802.3at Type 1 and 2
• Chipset Provides Electrical Isolation
• Reduced BOM Cost
• Eliminates up to 6 High Speed Opto-Couplers
• Eliminates Isolated 3.3V Power Supply
• Low Power Dissipation
• 0.25Ω Sense Resistance Per Channel
• Very High Reliability 4-Point PD Detection
• 2-Point Forced Voltage
• 2-Point Forced Current
• V_EE and V_PORT Monitoring
• 1 Second Rolling I_PORT Averaging
• Supports 2-Pair and 4-Pair Output Power
• 1MHz I²C Compatible Serial Control Interface
• Available In Three Power Grades
• A-Grade – LTPoE++™ 38.7W to 90W
• B-Grade – PoE+ 25.5W
• C-Grade – PoE 13W
• Available In 52-Lead 7mm × 8mm (LTC4270) and 24‑Lead 4mm × 4mm (LTC4271) QFN Packages

Typical Application

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-R_DS(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 fast shut-down of preselected ports. Advanced power management host software is available under a no-cost license. PD discovery uses a proprietary dual-mode 4-point detection mechanism ensuring excellent immunity from false PD detection. Midspan PSEs are supported with 2-event classification and a 2 second backoff timer. The LTC4270/LTC4271 includes an I²C serial interface operable up to 1MHz.

The LTC4270/LTC4271 is available in multiple power grades allowing delivered PD power up to 90W.