AD9879 Datasheet, PDF (1/24 Pages) Analog Devices – Mixed-Signal Front End Set-Top Box, Cable Modem

a
Mixed-Signal Front End
Set-Top Box, Cable Modem
AD9879
FEATURES
Low Cost 3.3 V MxFE™ for
DOCSIS EURO DOCSIS DVB DAVIC Compliant
Set-Top Box and Cable Modem Applications
232 MHz Quadrature Digital Upconverter
12-Bit Direct IF DAC (TxDAC+™)
Up to 65 MHz Carrier Frequency DDS
Programmable Sampling Clock Rates
16؋ Upsampling Interpolation LPF
Single-Tone Frequency Synthesis
Analog Tx Output Level Adjust
Direct Cable Amp Interface
12-Bit, 33 MSPS Direct IF ADC
with Optional Video Clamping Input
10-Bit, 33 MSPS Direct IF ADC
Dual 7-Bit, 16.5 MSPS Sampling I/Q ADC
12-Bit Sigma-Delta Auxiliary DAC
APPLICATIONS
Cable Modem and Satellite Systems
Set-Top Boxes
Power Line Modem
PC Multimedia
Digital Communications
Data and Video Modems
QAM, OFDM, FSK Modulation
FUNCTIONAL BLOCK DIAGRAM
TX DATA
SPORT
RXIQ[3:0]
RXIF[11:0]
I
Tx Q 16
SINC–1 ¹² _DAC
TX
DDS
4
CONTROL REGISTERS
⌺-⌬
PLL
XM/N
⌺-⌬_OUT
CAPORT
MCLK
MUX
8
ADC
MUX
10
ADC
12
ADC
AD9879
2
MUX ₂
RXI
RXQ
RX10
MUX
CLAMP
RX12
VIDEO
GENERAL DESCRIPTION
The AD9879 is a single-supply cable modem/set-top box mixed
signal front end. The device contains a transmit path interpolation
filter, a complete quadrature digital upconverter, and a transmit
DAC. The receive path contains a 12-bit ADC, a 10-bit ADC,
and dual 7-Bit ADCs. All internally required clocks and an output
system clock are generated by the PLL from a single crystal or
clock input.
The transmit path interpolation filter provides an upsampling
factor of 16× with an output signal bandwidth as high as 8.3 MHz.
Carrier frequencies up to 65 MHz with 26 bits of frequency tuning
resolution can be generated by the direct digital synthesizer
(DDS). The transmit DAC resolution is 12 bits and can run at
sampling rates as high as 232 MSPS. Analog output scaling from
0 dB to 7.5 dB in 0.5 dB steps is available to preserve SNR when
reduced output levels are required.
The 12-bit and 10-bit IF ADCs can convert direct IF inputs up
to 70 MHz and run at sample rates up to 33 MSPS. A video
input with an adjustable signal clamping level, along with the
10-bit ADC, allow the AD9879 to process an NTSC and a
QAM channel simultaneously.
The programmable sigma-delta DAC can be used to control
external components, such as variable gain amplifiers (VGAs) or
voltage controlled tuners. The CA PORT provides an interface to
the AD8321/AD8323 or AD8322/AD8327 programmable gain
amplifier (PGA) cable drivers enabling host processor control via
the MxFE SPORT. The AD9879 is available in a 100-lead
MQFP package. It offers enhanced receive path undersampling
performance and lower cost when compared with the pin compat-
ible AD9873. The AD9879 is specified over the commercial
(–40°C to +85°C) temperature range.
MxFE and TxDACÏ© are trademarks 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 that
may result from its use. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices.
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© Analog Devices, Inc., 2002