LTC4264

15

4264f

thermal shutdown. For DC loads the maximum ambient

temperature can be calculated as:

ture,

(43°C/W), and PWR is the power dissipation for the

EXTERNAL INTERFACE AND COMPONENT SELECTION

Transformer

Nodes on an Ethernet network commonly interface to

the outside world via an isolation transformer (Figure 9).

For powered devices, the isolation transformer must

include a center tap on the media (cable) side. Proper

termination is required around the transformer to provide

correct impedance matching and to avoid radiated and

conducted emissions. For high power applications beyond

IEEE 802.3af limits, the increased current levels increase

the current imbalance in the magnetics. This imbalance

reduces the perceived inductance and can interfere with

data transmission. Transformers specifically designed for

high current applications are required. Transformer vendors

such as Bel Fuse, Coilcraft, Halo, Pulse, and Tyco (Table 4)

can provide assistance with selection of an appropriate

isolation transformer and proper termination methods.

These vendors have transformers specifically designed

for use in high power PD applications.

16

14

15

1

3

2

6

3

2

RJ45

T1

PULSE H2019

4264 F09

1

7

8

5

4

11

9

10

6

8

7

D3

SMAJ58A

TVS

BR1

HD01

BR2

HD01

TO PHY

GND

LTC4264

C1

C14

0.1

µF

100V

Figure 9. PD Front-End with Isolation Transformer, Diode Bridges, Capacitors and TVS

APPLICATIONS INFORMATION

Table 4. Power over Ethernet Transformer Vendors

VENDOR

CONTACT INFORMATION

Bel Fuse Inc.

206 Van Vorst Street

Jersey City, NJ 07302

Tel: 201-432-0463

www.belfuse.com

Coilcraft Inc.

1102 Silver Lake Road

Gary, IL 60013

Tel: 847-639-6400

www.coilcraft.com

Halo Electronics

1861 Landings Drive

Mountain View, CA 94043

Tel: 650-903-3800

www.haloelectronics.com

Pulse Engineering

12220 World Trade Drive

San Diego, CA 92128

Tel: 858-674-8100

www.pulseeng.com

Tyco Electronics

308 Constitution Drive

Menlo Park, CA 94025-1164

Tel: 800-227-7040

www.circuitprotection.com