LXT975B datasheet(43/74 Pages) INTEL

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Fast Ethernet 10/100 Quad Transceivers — LXT974/LXT975

Datasheet

3.2

Magnetics Information

The LXT974/975 requires a 1:1 ratio for the receive transformers and a 2:1 ratio for the transmit

transformers as shown in Table 21. The transformer isolation voltage should be rated at 2 kV to

protect the circuitry from static voltages across the connectors and cables.

Refer to the Magnetic Manufacturers Cross Reference Guide (Application Note 73) for a list of

suitable magnetic manufacturers and part numbers. The latest version is located on the Intel web

site (http://developer.intel.com/design/network/). Suitable Magnetic part numbers are provided as a

reference only. Before committing to a specific component, designers should contact the

manufacturer for current product specifications, and validate the magnetics for a specific

application.

3.2.1

Magnetics With Improved Return Loss Performance

Intel is working with magnetic vendors to develop magnetic modules with improved return loss

characteristics. These improved magnetics simplify the design requirements for meeting ANSI

X3.263 return loss specifications.

Table 21. Magnetics Requirements

Parameter

Min

Nom

Max

Units

Test Condition

Rx turns ratio

–

1 : 1

––

Tx turns ratio

–

2 : 1

––

Insertion loss

0.0

–

1.1

80 MHz

Primary inductance

350

––

µH

Transformer isolation

–

Differential to common mode rejection

––

.1 to 60 MHz

––

60 to 100 MHz

Return Loss - Standard

––

-16

30 MHz

––

-10

80 MHz

Return Loss - Improved

––

-20

30 MHz

––

-15

80 MHz

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