IEEE 802.3bt PD with Telemetry and Power Priority

The LTC9105 is an IEEE 802.3af/at/bt ("PoE 2") Power over Ethernet (PoE) powered device (PD) controller with input current, voltage, and power telemetry. The LTC9105 includes an I2C interface to read telemetry, power sourcing equipment (PSE) allocated power, and auxiliary input status, and to write power input priority. The LTC9105 also features a configurable downstream power-up disable with under-power indication when the PSE allocated power is less than the PD requested power.

The LTC9105 utilizes an external, low RDS(ON), N-Channel, Hot Swap MOSFET, and a 50mΩ current sense resistor, and supports the LT4321 ideal bridge to extend the end-to-end power delivery efficiency. Also included are a power good output, external signature resistor, resistor programmable classification and pin-configurable PD requested Class. The presence of an auxiliary power supply is sensed at the AUX pin and reported through the I2C interface. Automatic maintain power signature (MPS) circuitry keeps the PD interface powered when downstream current draw falls below an internal MPS threshold.

Two dedicated Delta-Sigma ADCs continuously measure PD controller input voltage and current with a typical conversion time of 100ms and with 14-bit resolution. Simultaneous conversion of current and voltage measurements enables high-accuracy power calculations.

* IEEE 802.3bt Powered Device (PD) Controller

* 400kHz I2C Interface

* Continuous Voltage, Current, and Power Telemetry

* Dedicated 14-Bit Delta-Sigma Current and Voltage ADCs

* Automatic Maintain Power Signature (MPS)

* Supports Up to 90W PDs with Extended Power

* 5-Event Classification Sensing with PSE Allocated Power Readback