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FEATURES
13 MHz Master Clock Frequency
0 V to +2.5 V or ؎1.25 V Input Range
Single Bit Output Stream
90 dB Dynamic Range
Power Supplies
AVDD, DVDD: 5 V ؎ 5%
DVDD1: 3 V ؎ 5%
Logic Outputs 3 V/5 V Compatible
On-Chip 2.5 V Voltage Reference
48-Lead LQFP
Dual CMOS ⌺-⌬ Modulators
AD7724
FUNCTIONAL BLOCK DIAGRAM
REF1 REF2A
REF2B
2.5V
REFERENCE
AD7724
AVIN(+)
⌺-⌬
MODULATOR A
AVIN(–)
ADATA
SCLK
BVIN(+)
⌺-⌬
MODULATOR B
BVIN(–)
BDATA
XTAL OFF
CLOCK
CIRCUITRY
MZERO
XTAL1
XTAL2/MCLK
GC
CONTROL
LOGIC
BIP
STBY
DVAL
RESET
DVDD
DVDD1
DGND
AVDD
AGND
GENERAL DESCRIPTION
This device consists of two seventh order sigma-delta modulators. Each modulator converts its analog input signal into a high
speed 1-bit data stream. The part operates from a 5 V power
supply and accepts a differential input range of 0 V to +2.5 V or
±1.25 V centered about a common-mode bias. The analog inputs
are continuously sampled by the analog modulators, eliminating
the need for external sample-and-hold circuitry. The input
information is contained in the output stream as a density of
ones. The original information can be digitally reconstructed
with an appropriate digital filter.
The part provides an accurate on-chip 2.5 V reference for each
modulator. A reference input/output function is provided to
allow either the internal reference or an external system reference to be used as the reference source for the modulator.
The device is offered in a 48-lead LQFP package and designed
to operate from –40°C to +85°C.
REV. B
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.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 2002
