DC1814A-D: 90W LTPoE++

Demonstration circuit 1814A features the LTC®4274A, single port power sourcing equipment (PSE) controller, capable of delivering up to 90W of LTPoE++™ power to a compatible LTPoE++ powered device (PD). A proprietary detection / classification scheme allows mutual identification between an LTPoE++ PSE and LTPoE++ PD while remaining compatible and interoperable with existing Type 1 (13W) and Type 2 (25.5W) PDs. The LTC4274A feature set is a superset of the popular LTC4274. These PSE controllers utilize low RON external MOSFETs and 0.25Ω sense resistors which are especially important at the LTPoE++ current levels to maintain the lowest possible heat dissipation.

The LTC4274A is available in multiple power grades, allowing delivered PD power of 13W, 25.5W, 38.7W, 52.7W, 70W and 90W. The DC1814A has four variations DC1814A-A, DC1814A-B, DC1814A-C, and DC1814A-D which accommodate the LTPoE++ power levels (Table 1).

The LTC4274A is configured in the DC1814A as an AUTO pin high, MID pin high, autonomous midspan power injector; input data from an existing network system is sent out, along with power, to a PD. The LTC4274A autonomously detects a PD, turns power on to the port, and disconnects port power without the need for a microcontroller. A single 55V supply is required to power the DC1814A. A simple LDO regulator circuit on the board powers the digital supply of the LTC4274A. A SHDN pushbutton shuts down the port and disables detection. A RESET pushbutton resets the LTC4274A to the AUTO pin high state.