a
FEATURES
Low-Cost 3.3 V CMOS Analog Front End Converter for
MCNS-DOCSIS, DVB, DAVIC-Compliant
Set-Top Box, Cable Modem Applications
232 MHz Quadrature Digital Upconverter
DC to 65 MHz Output Bandwidth
12-Bit Direct IF D/A Converter (TxDAC+ ®)
Programmable Reference Clock Multiplier (PLL)
Direct Digital Synthesis
Interpolator
SIN(x)/x Compensation Filter
Four Programmable, Pin-Selectable Modulator Profiles
Single-Tone Mode for Frequency Synthesis Applications
12-Bit, 33 MSPS Sampling Direct IF A/D Converter with
Auxiliary Automatic Clamp Video Input Multiplexer
10-Bit, 33 MSPS Sampling Direct IF A/D Converter
Dual 8-Bit, 16.5 MSPS Sampling IQ A/D Converter
Two Independently Programmable Sigma-Delta
Converters
Direct Interface to AD8321/AD8323 PGA Cable Driver
Programmable Frequency Output
Power-Down Modes
Analog Front End Converter for
Set-Top Box, Cable Modem
AD9873
FUNCTIONAL BLOCK DIAGRAM
AD9873
COS
Tx IQ
Tx
Tx SYNC
INTERPOLATOR
FILTER
INV
SINC
12
DAC
Tx
SIN
3
PLL
SERIAL ITF
PROFILE
CA
DDS
12
4
CONTROL FUNCTIONS
2
SDELTA0
12
SDELTA1
REF CLK
8
Rx IQ
Rx IF
Rx SYNC
8
ADC
IIN
ADC
QIN
ADC
IF10
Rx
10
12
IF12
ADC
MUX
VIDEO
APPLICATIONS
Cable and Satellite Systems
PC Multimedia
Digital Communications
Data and Video Modems
Cable Modem
Set-Top Boxes
Powerline Modem
Broadband Wireless Communication
GENERAL DESCRIPTION
The AD9873 integrates a complete 232 MHz quadrature
digital transmitter and a multichannel receiver with four highperformance analog-to-digital converters (ADC) for various
video and digital data signals. The AD9873 is designed for cable
modem set-top box applications, where cost, size, power dissipation, and dynamic performance are critical attributes. A single
external crystal is used to control all internal conversion and
data processing cycles.
The transmit section of the AD9873 includes a high-speed
direct digital synthesizer (DDS), a high-performance, high-speed
12-bit digital-to-analog converter (DAC), programmable clock
multiplier circuitry, digital filters, and other digital signal
processing functions, to form a complete quadrature digital
up-converter device.
On the receiver side, two 8-bit ADCs are optimized for IQ
demodulated “out-of band” signals. An on-chip 10-bit ADC
is typically used as a direct IF input of 256 QAM modulated
signals in cable modem applications. A second direct IF input
and an auxiliary video input with automatic programmable clamp
function are multiplexed to a high-performance 12-bit video ADC.
The chip’s programmable sigma-delta modulated outputs and
an output clock may be used to control external components
such as programmable gain amplifiers (PGA) and mixer stages.
Three pins provide a direct interface to the AD8321/AD8323
programmable gain amplifier (PGA) cable driver.
The AD9873 is available in a space-saving 100-lead MQFP package.
TxDAC+ is a registered trademark of Analog Devices, Inc.
REV. 0
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
World Wide Web Site: http://www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 2000
