Product Brief
ICS1893AF
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 61.9Ω 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 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, 50Ω−characteristic impedance is desirable.
ICS1893 Transmit Twisted Pair
Page 7
Document Revision: 5 April 2002
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