ICS1893AF datasheet(27/137 Pages) RENESAS

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Chapter 6

Interface Overviews

ICS1893AF, Rev. D 10/26/04

October, 2004

ICS1893AF Data Sheet - Release

6.3.1

Twisted-Pair Transmitter Interface

The twisted-pair transmitter driver uses an H-bridge configuration. ICS suggests any of the following 1:1

10/100 Magnetics:

• Halo TG22S012ND

• Midcom 6120-37

Figure 6-1 shows the design for the ICS1893AF 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 ICS1893AF TP_TXP and TP_TXN

pins.

• The ICS1893AF supplies the power to the transformer. (No VDD connection is required.)

• The ICS1893AF TP_CT pin is connected directly to the transformer transmit center tap connection and

is bypassed to ground with a 100-pF capacitor. The transformer center tap must not connect to the

resistor/inductor network.

Note:

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

Keep all TX traces as short as possible.

When making board traces, 50

Ω-characteristic impedance is desirable.

Figure 6-1.

ICS1893AF Transmit Twisted Pair

ICS1893AF

61.9

Ω 1%

120 nH

61.9

Ω 1%

To RJ-45

1:1

System Ground Plane

Chassis Ground Plane

Ω

0.1

µF

Separate Ground Plane

Ideally, for these traces Zo = 50Ω.

Center

Tap

100 pF

TP_TXP 12

TP_TXN 13

TP_CT 10

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