10/2001

ARA2008

Reverse Amplifier with Step Attenuator

ADVANCED PRODUCT INFORMATION - Rev 0.0

FEATURES

· Low cost integrated amplifier with step

attenuator

· Attenuation Range: 0-58 dB, adjustable in

1dB increments via a 3 wire serial control

· Meets DOCSIS distortion requirements at

+60dBmV output signal level

· Low distortion and low noise

· Frequency range: 5-100MHz

· 5 Volt operation

APPLICATIONS

· MCNS/DOCSIS Compliant Cable Modems

· CATV Interactive Set-Top Box

· Telephony over Cable Systems

· OpenCable Set-Top Box

· Residential Gateway

The ARA2008 is designed to provide the reverse path

amplification and output level control functions in a

CATV Set-Top Box or Cable Modem. It incorporates

a digitally controlled precision step attenuator that is

preceded by an ultra low noise amplifier stage, and

followed by an ultra-linear output driver amplifier. This

device uses a balanced circuit design that exceeds

the MCNS/DOCSIS requirement for harmonic

performance at a +60dBmV output level while only

requiring a single polarity +5V supply. Both the input

and output are matched to 75 ohms with an

appropriate transformer. The precision attenuator

provides up to 58 dB of attenuation in 1 dB increments

via a three-wire serial interface. With external passive

components, this device meets IEC 1000-4-12 and

ANSI/IEEE C62.41-1991 100KHz ringwave tests, as

well as IEC1000-4-5 1.2/50mS surge tests. The

ARA2008 is offered in a 20-pin SSOP package.

PRODUCT DESCRIPTION

Figure 1. Cable Modem or Set Top Box Application Diagram

20 Pin SSOP Package

Diplexer

ARA2008

SAW

Filter

Double-

Conversion

Tuner

MAC

Upstream

QPSK/16QAM

Modulator

QAM Receiver

with FEC

Balun

Low Pass

Filter

Transmit Enable/Disable

Enable

Data

Clock

Microcontroller

with Ethernet

MAC

RAM

ROM

10Base-T

Transceiver

RJ45

Connector

Clock

Clock

Data

Data

54-860 MHz

44 MHz

5-42 MHz