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AN84REV1

CS8920 Technical Reference Manual

2.3 Recommended Magnetics for the

CS8920

The CS8920 is has two types of Ethernet

interfaces 10BASE-T and AUI. For both

the interfaces, analog filters are on the chip.

The Figure 2.3.1 shows typical connection

required for either of these interfaces.

Please refer to the data sheet of the CS8920

for values of the terminating resistors.

For an AUI interface, an isolation

transformer without a common mode choke

(CMC) is used.

For the 10BASE-T interface, choice

between isolation transformer and isolation

transformer with a common mode choke

(CMC) depends on the common mode

noise that exists on the 10BASE-T lines in

a particular system. A common mode

choke reduces common mode noise emitted

by the 10BASE-T lines. A CMC may be

required in certain applications to meet

EMI requirements and to meet 10BASE-T

common mode output voltage noise

specification. The physical dimensions of

the isolation transformer and the isolation

transformer with a CMC are the same.

Both are typically available in a 16 pin DIP

or 16 pin SOIC package.

The table 2.3.1 thru 2.3.3 provides

information regarding recommended

transformers and contacts for some of the

vendors. Several other vendors also make

transformers that are compatible with the

ones these tables.

CS8920

Figure 2.3.1. Typical CS8920 Ethernet Connection

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