SLXT915QC.B3 Intel, SLXT915QC.B3 Datasheet - Page 20

• Manufacturer Part Number: SLXT915QC.B3
• Description: IC QUAD ETHERNET REPEATER 64-QFP
• Manufacturer: Intel
• Type: Repeaterr

Specifications of SLXT915QC.B3

• Rohs Status: RoHS non-compliant
• Tx/rx Type: Ethernet
• Voltage - Supply: 4.75 V ~ 5.25 V
• Current - Supply: 240mA
• Mounting Type: Surface Mount
• Package / Case: 64-QFP
• Delay Time: -
• Capacitance - Input: -
• Lead Free Status / Rohs Status: Not Compliant
• Other names: 831529

Intel
3.0
3.1
3.1.1
3.1.2
3.2
20
®
LXT915 Simple Quad Ethernet Repeater
Application Information
Layout Requirements
The Twisted Pair Interface
The four, twisted-pair output circuits are identical. Each TPDOP/TPDON signal has a 24.9 Ω, 1%,
series resistor and a 120 pF capacitor differentially across the positive and negative outputs. These
signals go directly to a 1:√2 transformer creating the necessary 100 Ω termination for the cable.
The TPDIP/TPDIN signals have a 100 Ω resistor across the positive and negative input signals to
terminate the 100 Ω signal received from the line. To calculate the impedance on the output line
interface, use:
The layout of the twisted-pair ports is critical in complex designs. Run the signals directly from the
device to the discrete termination components (located close to the transformers).
The signals running from the transformers to the connector should run in close pairs directly to the
connector. Be careful not to cross the transmit and receive pairs. One way to avoid a problem is to
run the receive pairs on the component side and the transmit pairs on the solder side. Careful
planning during the schematic and layout stages can avoid these problems.
The PCB layout should have no ground or power planes from the transformers to the connectors.
The data signals should be the only traces in this area. Place the chassis ground for the connectors
near the edge of the PCB, away from the signals, connecting the connector shield with the chassis.
The RBIAS Pin
The RBIAS signal sets the levels for the output drivers of the LXT915. Any emissions or common
mode noise entering the device here could be measured on the twisted pair output signals. The
LXT915 requires a 12.4 kΩ, 1% resistor directly connected to RBIAS at pin 26. This connection
should be as short as possible. The ground rails from pins 25 & 27 should come directly off of the
device to enclose the resistor and pin forming a shielded area between the RBIAS connection and
the switching signals on the PCB.
Unmanaged Hub Application
Figure 6
LXT915s connected using the Asynchronous IRB mode.
Figure 6
a single collision LED. In LED Mode 1, the twisted pair port LEDs display link integrity only
(refer to
and pulling LEDM1 Low with pin 24 attached to ground.
Table
(Sheet 1) has the LXT915 set up with the LEDs in Mode 1 with one link LED per port and
shows an eight-port unmanaged hub application. The application shows a pair of
8). LED Mode 1 is selected by pulling LEDM0 High with a 1 kΩ resistor on pin 7
(24.9 Ω + 24.9 Ω)
*
√2
2
≈ 100 Ω.
Datasheet