ICS1893AFLF Datasheet, PDF (27/136 Pages) Integrated Device Technology – 3.3-V 10Base-T/100Base-TX Integrated PHYceiver™

ICS1893AF Data Sheet - Release
Chapter 6 Interface Overviews
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 61.9Ω 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:
1. If the transmit transformer has a choke, it may be put on the chip side, the RJ-45 side, or both.
2. Keep all TX traces as short as possible.
3. When making board traces, 50Ω-characteristic impedance is desirable.
Figure 6-1. ICS1893AF Transmit Twisted Pair
System Ground Plane Chassis Ground Plane
TP_TXP 12
ICS1893AF
61.9Ω 1%
120 nH
1:1
Center
Tap
61.9Ω 1%
TP_TXN 13
TP_CT 10
Ideally, for these traces Z_o = 50Ω.
100 pF
Separate Ground Plane
To RJ-45
75Ω
0.1 µF
ICS1893AF, Rev. D 10/26/04
Copyright © 2004, Integrated Circuit Systems, Inc.
All rights reserved.
27
October, 2004