Product Brief

ICS1893AF

Page 7

Document Revision: 5 April 2002

Typical Board Layouts

Twisted-Pair Transmitter Interface

The twisted-pair transmitter driver uses an H-bridge configuration. .

ICS suggests using any of the following for the H-bridge:

•

Halo TG22S012ND transformer

•

Transpower HB617-LP transformer

•

Pulse 68517 transformer which can be turned around to move the choke windings to the RJ-45 side.

The figure below shows the design for the ICS1893 twisted-pair transmitter interface.

•

Two 61.9

Ω 1% resistors are in series, with a 120-nH 5% inductor between them. These components form

a network that connects across both the transformer and the ICS1893 TP_TXP and TP_TXN pins.

•

The ICS1893 transmitter output H drive configuration supplies power to the transformer. (No VDD

connection is required.)

•

The ICS1893 TP_CT pin is connected directly to the transformer transmit center tap connection and is

bypassed to ground with a 100pF capacitor.

Note:

1. If the transformer has a choke, it may be put on the chip side, RJ-45 side or both.

2. Keep all TX traces as short as possible.

3.

When making board traces, 50

Ω−characteristic impedance is desirable.

ICS1893 Transmit Twisted Pair