SLXT973QE Cortina Systems Inc, SLXT973QE Datasheet - Page 45

• Manufacturer Part Number: SLXT973QE
• Manufacturer: Cortina Systems Inc

Specifications of SLXT973QE

• Lead Free Status / RoHS Status: Not Compliant

LXT973 Transceiver
Datasheet
249426, Revision 6.0
13 July 2007
4.1.6
4.1.7
Table 11
Cortina Systems
Twisted-Pair Interface
Use the following standard guidelines for a twisted-pair interface:
Magnetics Information
The LXT973 Transceiver requires a 1:1 ratio for the receive transformers and a 1:1 ratio
for the transmit transformers. The transformer isolation voltage should be rated at 2 kV to
protect the circuitry from static voltages across the connectors and cables. The LXT973
Transceiver is a current-driven transceiver that requires an external voltage (center tap) to
drive the transmit signal. To support LXT973 Transceiver auto MDI/MDIX functionality, the
magnetic must provide a center tap for both transmit and receive magnetic windings, with
both connected to VCCT (see
function, select a magnetic so that both transmit and receive windings are matched or
balanced (refer to the LXT973 Transceiver Design and Layout Guide – document number
249631). Refer to
component, designers should contact the manufacturer for current product specifications,
and validate the magnetics for the specific application.
Magnetics Requirements
®
Rx turns ratio
Tx turns ratio
Insertion loss
Primary inductance
Transformer
isolation
Differential to
common mode
rejection
Return Loss
• Place the magnetics as close as possible to the LXT973 Transceiver.
• Keep transmit pair traces as short as possible; both traces should have the same
• Avoid vias and layer changes as much as possible.
• Keep the transmit and receive pairs apart to avoid cross-talk.
• Route the transmit pair adjacent to a ground plane. The optimum arrangement is to
• Improve EMI performance by filtering the TPO center tap. A single ferrite bead rated
LXT973 10/100 Mbps Dual-Port Fast Ethernet PHY Transceiver
length.
place the transmit traces two to three layers from the ground plane with no intervening
signals.
at 100 mA may be used to supply center tap current to all ports.
Parameter
Table 11
Min
350
-16
-10
0.0
40
35
–
–
2
Nom
1:1
1:1
0.6
for transformer requirements. Before committing to a specific
–
–
–
–
–
–
Figure 13 on page
Max
1.1
–
–
–
–
–
–
–
–
Units
dB
μ H
kV
dB
dB
dB
dB
–
–
Test Condition
60 to 100 MHz
47). When using the auto MDI/MDIX
.1 to 60 MHz
30 MHz
80 MHz
–
–
–
–
–
4.1 Design Recommendations
Page 45