AD9873

Manufacturer Part NumberAD9873
DescriptionAnalog Front End Converter for Set-top Box, Cable Modem, and Other Broadband Communication Applications
ManufacturerAnalog Devices
AD9873 datasheet
 


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GENERAL DESCRIPTION
The AD9873 integrates a complete 232 MHz quadrature
digital transmitter and a multichannel receiver with four high-
performance 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 dissi-
pation, 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.
TxDAC+ is a registered trademark of Analog Devices, Inc.
Analog Front End Converter for
Set-Top Box, Cable Modem
FUNCTIONAL BLOCK DIAGRAM
COS
Tx IQ
INTERPOLATOR
Tx
FILTER
Tx SYNC
SIN
PLL
DDS
4
SERIAL ITF
CONTROL FUNCTIONS
2
PROFILE
8
8
Rx IQ
Rx IF
Rx
Rx SYNC
10
12
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.
AD9873
AD9873
12
INV
Tx
DAC
SINC
3
CA
12
SDELTA0
12
SDELTA1
REF CLK
I
ADC
IN
Q
ADC
IN
IF10
ADC
IF12
MUX
ADC
VIDEO

AD9873 Summary of contents