CS8952 datasheet(67/82 Pages) CIRRUS

67 / 82 page

CS8952

CrystalLAN™ 100BASE-X and 10BASE-T Transceiver

ly) on both sides of the TX+/- traces.

•

No signal current carrying planes, i.e. no

ground or power plane, should be present un-

derneath the region between the transformer

secondary (network) side and the RJ-45. How-

ever,a chassisplane maybeaddedinthisre-

gion to pick up the metal tabs of a shielded RJ-

45. This chassis plane should be separated from

the ground and power planes by at least

50 mils. That is, all other ground and power

planes should be “cookie cuttered” so they are

voided in the area of the chassis plane. Gener-

ally speaking, parts should not cross the moat

except for the transformer.

•

Proper termination practices must be used with

all transmission lines, especially if sending and

receiving high speed signals on and off the

board. Series terminations must be kept close to

the source and load terminations close to the

load. Thus the TX_NRZ+/- termination com-

ponents must be kept close to the fiber optic

transceiver, and the RX_NRZ+/- and SIG-

NAL+/- termination components must be kept

close to the CS8952.

•

Locate the crystal as close to the CS8952 as

possible, running short traces on the component

side in order to reduce parasitic load capaci-

tance.

•

Add bulk capacitance at each connector where

power may be supplied. For example, MII pow-

er may be provided at the MII connector and at

a separate connector for test purposes. If so, and

the two connectors are not adjacent, then the

bulk capacitors should be duplicated in each lo-

cations.

•

Use wide traces to connect the “Bob Smith” ter-

mination resistors at T1 and the RJ-45 to the

2 KV capacitor or capacitors in order to mini-

mize their lead inductance.

CS8952 Pin

Assignment

T1 Primary Pin

Assignment

T1 Secondary

Pin Assignment

RJ-45 Pin Assignment

Adapter/NIC

Configuration

Hub/Repeater

Configuration

91 (RX+)

1 (RX+)

7 (RX+)

3 (RD+)

1 (RD+)

92 (RX-)

2 (RX-)

6 (RX-)

6 (RD-)

2 (RD-)

81 (TX-)

16 (TX-)

10 (TX-)

2 (TD+)

6 (TD-)

80 (TX+)

15 (TX+)

11 (TX+)

1 (TD+)

3 (TD+)

Table 8. RJ-45 Wiring

CS8952 Datasheet(PDF) 67 Page - Cirrus Logic

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