DC1145B: 12V @ 0.9A POE, 37 ~ 57V in

Summary

Demonstration circuit 1145B, featuring the LTC®4267, provides a complete IEEE 802.3af Powered Device (PD) interface and isolated 12V at 0.9A power supply solution for use in Power over Ethernet (PoE) applications. An optional connection is included for a 12V auxiliary supply on the secondary side that disables PoE when present.

The LTC4267 integrates the 25k signature resistor, classification current source, thermal overload protection, signature disable and power good signal along with an undervoltage lockout optimized for use with the IEEE required diode bridge. The precision dual level input current limit allows the LTC4267 to charge load capacitors and interface with legacy PoE systems.

The LTC4267 combines the above features with a current mode switching controller designed for driving a 6V rated N-channel MOSFET. It features programmable slope compensation, soft-start, and constant frequency operation, minimizing electrical noise even with light loads.

Specifications

Manufacturer Analog Devices Inc.
Category Power Management
Sub-Category POE - Power Over Ethernet
Eval Board Part Number 505-DC1145B-ND
Eval Board Supplier Analog Devices Inc.
Eval Board Normally In Stock
Compliance IEEE 802.3af (802.3at Type 1)
Outputs and Type 1 Isolated
Voltage Out 12 V
Current Out 900 mA
Voltage In 37 ~ 57 V
Efficiency @ Conditions >85%, 57V in, 12V @ 0.5 ~ 0.9 A
>85%, 48V in, 12V @ 0.4 ~ 0.9 A
>83%, 37V in, 12V @ 0.3 ~ 0.9 A
Internal Switch No
Features Current Limit (Adj. or Fixed)
Power Good Output
Shutdown, Enable, Standby
Soft Start
Thermal Protection
Under Voltage Protection, Brown-Out
Voltage Reference
Switching Frequency 200 kHz
Component Count + Extras 52 + 21
Application / Target Market PoE, Power Over Ethernet
RF: WLAN Access Points
Security IP Camera
VOIP Phones
Design Author Linear Technology
Main I.C. Base Part LTC4267
Date Created By Author 2011-06
Date Added To Library 2013-12

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Support Documents & Media

DC1145B - User Guide LTC4267 - Datasheet

Media

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