EELXT905PC.C2 查看數據表（PDF） - Intel

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EELXT905PC.C2

Universal 10BASE-T Transceiver with 3.3V Support

Intel 

Universal 10BASE-T Transceiver with 3.3V Support — LXT905

3.0

Application Information

3.1

Introduction

Figure 8 on page 19 through Figure 10 on page 21 show typical LXT905 applications. These

diagrams group similar pins; they do not portray the actual chip pinout. The controller interface

pins; Transmit Data (TXD), Transmit Clock (TCLK) Transmit Enable (TEN), Receive Data

(RXD), Receive Clock (RCLK), Collision Signal (COL), and Carrier Detect (CD) pins are at the

upper left of the diagram.

Power and ground pins are at the bottom of each diagram. VCC1 and VCC2 use a single power

supply with decoupling capacitors installed between the power and ground busses. VCC may be

powered by a 5V or 3.3V supply.

3.1.1

Termination Circuitry

Several I/O pins are pulled-up or pulled-down internally to keep the signals from floating. It is

recommended to hard-wire these pins either High or Low. Externally pull-up pins (LEDT/PDN,

LEDC/FDE, LEDR, LEDL) and pull-down pins (LBK, TEN, TXD, DSQE, MDO, MDI)

separately using a 10k Ω, 1% resistor, or tie directly to VCC or ground.

3.1.2

Twisted-Pair Interface

The Twisted-Pair interface (TPOP/N and TPIP/N) is at the upper right of the diagram. The I/O

pairs have impedance-matching resistors for 100Ω UTP, but no external filters are required.

3.1.3

RBIAS Pin

The RBIAS pin sets the levels for the LXT905 output drivers. The LXT905 requires a 7.5k Ω, 1%

resistor directly connected between the RBIAS pin and ground. This resistor should be located as

close to the device as possible. Keep the traces as short as possible and isolated from all other high

speed signals.

3.1.4

Crystal Information

Based on limited evaluation, Table 4 lists some suitable crystals. Designers should test and validate

all crystals before committing to a specific component.

Table 4. Suitable Crystals

Manufacturer

MTRON

Part Number

MP-1

MP-2

Datasheet

17

Document #: 249271

Revision #: 002

Rev. Date: June 19, 2001

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