AM7996 查看數據表（PDF） - Advanced Micro Devices

零件编号

产品描述 (功能)

生产厂家

AM7996

IEEE 802.3/Ethernet/Cheapernet Transceiver

Advanced Micro Devices 

PIN DESCRIPTION

Attachment Unit Interface (AUI)

Dl+, Dl–

Receive Line Output (Differential Outputs)

This pair is intended to operate into terminated 78 Ω

transmission lines. Signals at RXT meeting bandwidth

requirements and carrier sense levels are outputted at

Dl±. Signaling at Dl ± meets requirements of

IEEE 802.3, Rev. D.

Cl+, Cl–

Collision Line Output (Differential Outputs)

This pair is intended to operate into terminated 78 Ω

transmission lines. Signal Quality Error (SQE), de-

tected at DO ± inputs (excessive transmissions) or RXT

input (during a collision), outputs the 10 MHz internal

oscillator signal to the AUI interface. For proper compo-

nent values at COLL OSC, signaling at Cl ± meets re-

quirements of IEEE 802.3, Rev. D.

DO+, DO–

Transmit Input (Differential Inputs)

A pair of internally biased line receivers consisting of a

squelch detect receiver with offset and noise filtering

and a data receiver with zero offset for data signal pro-

cessing. Signals meeting squelch requirements are

waveshaped and output at TXT.

Coaxial Media Interface (TAP)

RXT

Media Signal Receiver Input (Input)

RXT connects to the media through a 4:1 attenuator of

100 kΩ total resistance (25 kΩ and 75 kΩ in series).

Return for the attenuator is VCOL. RXT is an analog

input with internal AC coupling for Manchester data sig-

nals and direct coupling for Carrier Detect and SQE av-

erage level detection. Signals at RXT meeting carrier

squelch enable data to the Dl ± outputs. Data signals

are AC coupled to Dl ± with a 150 ns time constant,

high-pass filter. Signals meeting SQE levels enable

COLL OSC frequency to Cl ± outputs.

TXT

Tap Node Driver (Input/Output)

A controlled bandwidth current source and sense am-

plifier. This l/O port is to be connected to the media

through an isolation network and a low-pass filter. Sig-

nals meeting DO ± squelch and jabber timing require-

ments are output at TXT as a controlled rise and fall

time current pulse. When operated into a double termi-

nated 50 Ω transmission line, signaling meets

IEEE 802.3, Rev. D recommendations for amplitude,

pulse-width distortion, rise and fall times, and harmonic

content. The sense amplifier monitors TXT faults and

inhibits transmission.

Global Signals

VCREF

Timing Reference Set (Input)

VCREF is a compensated voltage reference input with

respect to VEE. When a resistor is connected between

VCREF and VEE, then internal transmit and receive

squelch timing, SQE oscillator frequency, and receive

and SQE output drive levels are set. SQE frequency

set is also determined by components connected be-

tween VCC1 and COLL OSC.

SQE TEST

Signal Quality Error Test Enable (Input)

The SQE Test function is enabled by connecting the

SQE TEST pin to VEE and disabled by connecting to VCC.

VTX+, VTX–

Tap Node Driver Current Set (Inputs)

A reference input for transmission level and external re-

dundant jabber. Transmit level is set by an external re-

sistor between VTX+ and VTX– (for an 80 mA peak level,

R = 9.09 Ω). VTX– may be operated between VEE and

VEE + 1 V. When the voltage at VTX– goes more positive

than VEE + 2 V, TXT is disabled and an SQE message

is output at the Cl pair.

TAP SHIELD

Low-Noise Media Cable Return (Input)

This input is the return for VCOL reference and the re-

ceive signal from the media. External connection is to

a positive power supply.

VCOL

SQE Reference Voltage (Bias Supply)

SQE sense voltage and RXT input amplifier reference.

An internally set analog reference for SQE level and data

signal set at –1.600 V nominal with a source resistance

of 150 Ω nominal. This reference should be filtered with

respect to TAP SHIELD (see Applications section for ad-

justing threshold levels for other applications).

COLL OSC

SQE Timing Set (Input)

Timing input for SQE oscillator. For a properly set input

at VCREF, SQE oscillator period is set at 2.1RC. For a

10 MHz SQE oscillator frequency, R should be 1 kΩ and

C 47 pF, including interconnect and device capacitance.

VCC1

Positive Logic Supply

VCC2

SQE Timing Reference (Positive Supply Voltage)

Timing reference return for SQE oscillator and analog

signal ground.

VEE

Negative Logic Supply and IC Substrate

4

Am7996

Share Link: