AD28MSP01 Datasheet, PDF (1/28 Pages) Analog Devices – PSTN Signal Port

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PSTN Signal Port
AD28msp01
FEATURES
Complete Analog l/O Port for DSP-Based FAX/MODEM
Applications
Linear-Coded 16-Bit Sigma-Delta ADC
Linear-Coded 16-Bit Sigma-Delta DAC
On-Chip Anti-Alias and Anti-lmage Filters
Digital Resampling/lnterpolation Filter
7.2 kHz, 8.0 kHz, and 9.6 kHz Sampling Rates
8/7 Mode for 8.23 kHz, 9.14 kHz, and 10.97 kHz
Sampling Rates
Synchronous and Asynchronous DAC/ADC Modes
Bit and Baud Clock Generation
Transmit Digital Phase-Locked Loop for Terminal
Synchronization
Independent Transmit and Receive Phase Adjustment
Serial Interface to DSP Processors
+5 V Operation with Power-Down Mode
28-Pin Plastic DlP/44-Lead PLCC/28-Lead SOIC
APPLICATIONS
High Performance DSP-Based Modems
V.32ter, V.32bis, V.32, V.22bis, V.22, V.21,
Bell 212A, 103
Fax and Cellular-Compatible Modems
V.33, V.29, V.27ter, V.27bis, V.27, V.26bis
Integrated Fax, Modem, and Speech Processing
FUNCTIONAL BLOCK DIAGRAM
ANALOG
INPUTS
16-BIT
SIGMA-DELTA
ADC
VOLTAGE
REFERENCE
RESAMPLING
INTERPOLATION
FILTER
SERIAL
PORT
DIGITAL
DATA AND
CONTROL
DIFFERENTIAL
ANALOG
OUTPUT
16-BIT
SIGMA-DELTA
DAC
CLOCK INPUTS
CLOCK OUTPUTS
CLOCK
GENERATION
GENERAL DESCRIPTION
The AD28msp01 is a complete analog front end for high perfor-
mance DSP-based modems. The device includes all data conver-
sion, filtering, and clock generation circuitry needed to imple-
ment an echo-cancelling modem with a single host digital signal
processor. Software-programmable sample rates and clocking
modes support all established modem standards. The AD28msp01
simplifies overall system design by requiring only +5 volts.
The inclusion of on-chip anti-aliasing and anti-imaging filters
and 16-bit sigma-delta ADC and DAC ensures a highly inte-
grated and compact solution for FAX or data MODEM applica-
tions. Sigma-delta conversion technology eliminates the need for
complex off-chip anti-aliasing filters and sample-and-hold circuitry.
The AD28msp01 utilizes advanced sigma-delta technology to
move the entire echo-cancelling modem implementation into the
digital domain. The device maintains a –72 dB SNR throughout
all filtering and data conversion. Purely DSP-based echo cancel-
lation algorithms can thereby maintain robust bit error rates
under worst-case signal attenuation and echo amplitude condi-
tions. The AD28msp01’s on-chip interpolation filter resamples
the received signal after echo cancellation in the DSP, freeing
the processor for other voice or data communications tasks.
On-chip bit and baud clock generation circuitry provides for
either synchronous or asynchronous operation of the transmit
(DAC) and receive (ADC) paths. Each path features indepen-
dent phase advance and retard adjustments via software control.
The AD28msp01 can also synchronize modem operation to an
external terminal bit clock.
The AD28msp01’s serial I/O port provides an easy interface to
host DSP microprocessors such as the ADSP-2101, ADSP-2105,
and ADSP-2111. Packaged in a 28-pin plastic DIP, 44-lead
PLCC, 44-pin TQFP, or 28-lead SOIC, the AD28msp01 pro-
vides a compact solution for space-constrained environments.
The device operates from a +5 V supply and offers a low power
sleep mode for battery-powered systems.
A detailed block diagram of the AD28msp01 is shown in
Figure 1.
REV. A
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otherwise under any patent or patent rights of Analog Devices.
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