16-Bit 900 kSPS ⌺-⌬ ADC with a
Programmable Postprocessor
AD7725
TYPICAL APPLICATIONS
Radar
Sonar
Auxiliary Car Functions
Medical Communications
FUNCTIONAL BLOCK DIAGRAM
AVDD
AGND
VIN (+)
VIN (–)
2.5V
REFERENCE
AD7725
MOD
POSTPROCESSOR
PRESET
FILTER
DVDD
DGND
DEFAULT FILTER
(ROM)
UNI
HALF PWR
STBY
SYNC
S/P
RD/WR
SOE/CS
CFMT/RS
DVAL/INT
SDI/DB0
REF2
REF1
XTAL
CLOCK
XTAL_OFF
XTAL
CLKIN
SMODE1/DB15
SMODE0/DB14
CONTROL
LOGIC
SCR/DB13
CFGEND/DB12
DB11
DB10
FSO/DB9
ERR/DB1
DB2
DB3
RESETCFG/DB4
INT/DB5
FSI/DB6
SCO/DB7
SDO/DB8
FEATURES
Programmable Filtering:
Any Characteristic up to 108 Tap FIR and/or IIR
Polynomial Signal Conditioning up to 8th Order
Programmable Decimation and Output Word Rate
Flexible Programming Modes:
Boot from DSP or External EPROM
Parallel/Serial Interface
Internal Default Filter for Evaluation
14.4 MHz Max Master Clock Frequency
0 V to +4 V (Single-Ended) or ؎2 V (Differential) Input
Range
Power Supplies: AVDD, DVDD: 5 V ؎ 5%
On-Chip 2.5 V Voltage Reference
44-Lead MQFP Package
GENERAL DESCRIPTION
The AD7725 is a complete 16-bit, ⌺-⌬ analog-to-digital converter with on-chip, user-programmable signal conditioning. The
output of the modulator is processed by three cascaded finite
impulse response (FIR) filters, followed by a fully user-programmable postprocessor. The postprocessor provides processing
power of up to 130 million accumulates (MAC) per second. The
user has complete control over the filter response, the filter coefficients, and the decimation ratio.
Filter Wizard allows the user to design different filter types
and generates the appropriate configuration file to be downloaded to the postprocessor. The AD7725 also has an internal
default filter for evaluation purposes.
The postprocessor permits the signal conditioning characteristics to be programmed through a parallel or serial interface. It
is programmed by loading a user-defined filter in the form of a
configuration file. This filter can be loaded from a DSP or an
external serial EPROM. It is generated using a digital filter
design package called Filter Wizard, which is available from the
AD7725 section on the Analog Devices website.
This part has an accurate on-chip 2.5 V reference for the modulator. A reference input/output function allows either the
internal reference or an external system reference to be used as
the reference source for the modulator.
It provides 16-bit performance for input bandwidths up to
350 kHz with an output word rate of 900 kHz maximum. The
input sample rate is set either by the crystal oscillator or an
external clock.
The device is available in a 44-lead MQFP package and is specified over a –40°C to +85°C temperature range.
REV. A
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. Trademarks and
registered trademarks are the property of their respective owners.
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© 2004 Analog Devices, Inc. All rights reserved.
