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Technical ArticlesLT4321/LT4275 LTPoE++/PoE+/PoE PD Controller TechClips
Features and Benefits
- IEEE 802.3af/at and LTPoE++™ Powered Device (PD) Controller
- LTPoE++ Supports Power Levels Up to 90W
- LT4275A Supports All of the Following Standards:
- LTPoE++ 38.7W, 52.7W, 70W and 90W
- IEEE 802.3at 25.5W Compliant
- IEEE 802.3af Up to 13W Compliant
- LT4275B is IEEE 802.3at/af Compliant
- LT4275C is IEEE 802.3af Compliant
- 100V Absolute Maximum Input Voltage
- Wide Junction Temperature Range (–40°C to 125°C)
- Overtemperature Protection
- Integrated Signature Resistor
- External Hot Swap™ N-Channel MOSFET for Lowest Power Dissipation and Highest System Efficiency
- Programmable Aux Power Support as Low as 9V
- Optional Support of Non-Standard Low Voltage PoE
- Available in 10-Lead MSOP and 3mm × 3mm DFN Packages
The LT4275 is a pin-for-pin compatible family of IEEE 802.3 and LTPoE++ powered device (PD) controllers.
The LT4275A employs a proprietary LTPoE++ classification scheme, delivering 38.7W, 52.7W, 70W or 90W of power at the PD RJ45 connector. The LT4275A is fully compatible with IEEE 802.3. The LT4275B is an IEEE 802.3at compliant, Type 2 (PoE+) PD delivering up to 25.5W. The LT4275C is an IEEE 802.3af compliant, Type 1 (PoE) PD delivering up to 13W.
The LT4275 internal charge pump provides an N-channel MOSFET solution, eliminating a larger and more costly P-channel MOSFET. A low RDS(ON) MOSFET also maximizes power delivery and efficiency, reduces power and heat dissipation, and eases thermal design. Startup inrush current is adjustable with an external capacitor. The LT4275 also includes a power good output, on-board signature resistor, undervoltage lockout, and thermal protection. The LT4275A/LT4275B drives a single opto-coupler to indicate the power level of the attached PSE. Pin-selectable support for non-standard low voltage operation is provided. Auxiliary power override is supported with the AUX pin.
The LT4275A can be configured to support all possible LTPoE++, 802.3at and 802.3af power levels with external component changes.
- High Power Wireless Data Systems
- Outdoor Security Camera Equipment
- Commercial and Public Information Displays
- High Temperature Industrial Applications
Product Lifecycle Production
At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
Evaluation Kits (4)
Demonstration circuit 2125 is a small, highly-integrated, non-isolated PoE Powered Device (PD) solution. It features a PD Interface Controller (LT4275), which interfaces with a PoE Power Sourcing Equipment (PSE), an ideal diode bridge controller (LT4321), which minimizes bridge losses, and a DC/DC μModule® regulator (LTM8027).
Tools & Simulations
LTspice® is a powerful, fast and free simulation software, schematic capture and waveform viewer with enhancements and models for improving the simulation of analog circuits.
Models for the following parts are available in LTspice:
Press Releases (1)
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.
Sample & Buy
The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.