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.
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 |
