LTC9105

RECOMMENDED FOR NEW DESIGNS

IEEE 802.3bt PD with Telemetry and Power Priority

Data Sheet (Rev. A) Product Selection Table

Part Models: 2
1ku List Price: Starting From $2.72

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Part Details

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

Seamless Switchover between Dual PD or PD/AUX Inputs
Superior Surge Robustness (100V Absolute Maximum)
Wide Junction Temperature Range (-40⁰C to 125⁰C)
External Hot Swap N-Channel MOSFET for Lowest Power Dissipation and Highest System Efficiency
50mΩ Current Sense Resistor
Auxiliary Input Sense with Standby Modes
20-Pin 5mm x 5mm QFN Package

Part Models: 2
1ku List Price: Starting From $2.72

Documentation

Data Sheet 1

LTC9105: IEEE 802.3bt PD with Telemetry and Power Priority Data Sheet (Rev.A) 03/03/2025

User Guide 1

EVAL-LTC9105-AZ User Guide: LTC9105, MAX5974C, LT4321, and ADuM1252 IEEE 802.3bt Powered Device with I2C Telemetry (Rev.0) 03/03/2025

ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well. "Zero defects" for shipped products is always our goal. View our quality and reliability program and certifications for more information.

Part Model	Pin/Package Drawing	Documentation	CAD Symbols, Footprints, and 3D Models
LTC9105ATP+	20L, THIN QFN, 5X5X0.75	Material Declaration Reliablity Data	Ultra Librarian SamacSys
LTC9105ATP+T	20L, THIN QFN, 5X5X0.75	Material Declaration Reliablity Data	Ultra Librarian SamacSys

This is the most up-to-date revision of the Data Sheet.

Software Resources

Evaluation Software 1

C API Documentation

The C API Documentation for this PD may be requested from the Software Request Form (SRF). This C API Documentation describes the I²C interface and programming details for the respective PD controller.

C API Documentation NEW

Evaluation Kits

EVAL-LTC9105-AZ: LTC9105, MAX5974C, LT4321, and ADuM1252 IEEE 802.3bt Powered Device with I2C Telemetry

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Features and Benefits

IEEE 802.3bt-compliant Class 6 PD
Port telemetry with an isolated I²C interface
5V/9.2A isolated synchronous forward converter

Product Details

The EVAL-LTC9105-AZ is an IEEE 802.3bt-compliant Type 3, Class 6 Power over Ethernet (PoE) powered device (PD) with port telemetry via I²C. The evaluation board features the LTC9105 PD interface controller, MAX5974C switching regulator controller, the LT4321 PoE ideal diode bridge controller, and the ADuM1252 I²C isolator.

The LTC9105 provides IEEE 802.3af-, IEEE 802.3at-, and IEEE 802.3bt-compliant interfacing with port voltage and current telemetry via I²C. It utilizes an external, low channel resistance, R_DS(ON) (34mΩ typical), N-channel, hot-swap metal-oxide semiconductor, field-effect transistor (MOSFET), and 50mΩ sense resistor. Automatic maintain power signature (MPS) keeps the port connected when the current drops to a low level.

The MAX5974C controls a DC/DC converter utilizing a highly efficient active-clamp forward converter topology with synchronous rectification and provides an isolated 5V/9.2A output. The LT4321 controls eight low R_DS(ON) (57mΩ typical), N-channel MOSFETs to further improve end-to-end power delivery efficiency and ease thermal design. The ADuM1252 isolates I²C data between the LTC9105 and a host controller on a nonisolated ground domain.

The EVAL-LTC9105-AZ is configured as a Class 6 PD and accepts up to 51W of delivered power from a power sourcing equipment (PSE) via its RJ45 connector (J1). The EVAL-LTC9105-AZ can be powered by a local 55V DC power supply using the auxiliary supply input terminals. With the DC590B I²C interface board connected to the EVAL-LTC9105-AZ, the EVAL-LTC9105-AZ graphical user interface (GUI) displays port telemetry and configuration options.

Resources

EVAL-LTC9105-AZ User Guide: LTC9105, MAX5974C, LT4321, and ADuM1252 IEEE 802.3bt Powered Device with I2C Telemetry (Rev.0)
1.35 M

EVAL-LTC9105-AZ - Design Files
3.93 M

EVAL-LTC9105-AZ - Schematic
316.93 K

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