a
FEATURES
Charge Balancing ADC
24 Bits, No Missing Codes
؎0.0015% Nonlinearity
2-Channel Programmable Gain Front End
Gains from 1 to 128
Differential Inputs
Low-Pass Filter with Programmable Filter Cutoffs
Ability to Read/Write Calibration Coefficients
Bidirectional Microcontroller Serial Interface
Internal/External Reference Option
Single- or Dual-Supply Operation
Low Power (25 mW Typ) with Power-Down Mode
(7 mW Typ)
Signal Conditioning ADC
AD7710
FUNCTIONAL BLOCK DIAGRAM
AVDD
DVDD
REF
REF
IN (–) IN (+)
REF OUT
2.5V REFERENCE
4.5A
CHARGE-BALANCING A/D
CONVERTER
AIN1(+)
AIN1(–)
M
U
X
AIN2(+)
AUTO-ZEROED
⌺-⌬
MODULATOR
PGA
DIGITAL
FILTER
SYNC
A = 1 – 128
AIN2(–)
AVDD
CLOCK
GENERATION
20A
APPLICATIONS
Weigh Scales
Thermocouples
Process Control
Smart Transmitters
Chromatography
VBIAS
AVDD
MCLK
IN
MCLK
OUT
SERIAL INTERFACE
CONTROL
REGISTER
IOUT
OUTPUT
REGISTER
AD7710
AGND DGND
VSS
RFS TFS MODE SDATA SCLK DRDY A0
GENERAL DESCRIPTION
The AD7710 is a complete analog front end for low frequency
measurement applications. The device accepts low level signals
directly from a strain gage or transducer and outputs a serial
digital word. It employs a sigma-delta conversion technique to
realize up to 24 bits of no missing codes performance. The input
signal is applied to a proprietary programmable gain front end
based around an analog modulator. The modulator output is
processed by an on-chip digital filter. The first notch of this
digital filter can be programmed via the on-chip control register,
allowing adjustment of the filter cutoff and settling time.
CMOS construction ensures low power dissipation, and a software programmable power-down mode reduces the standby
power consumption to only 7 mW typical. The part is available
in a 24-lead, 0.3 inch-wide, plastic and hermetic dual-in-line
package (DIP) as well as a 24-lead small outline (SOIC) package.
The part features two differential analog inputs and a differential reference input. Typically, one of the channels will be used
as the main channel with the second channel used as an auxiliary input to measure a second voltage periodically. It can be
operated from a single supply (by tying the VSS pin to AGND),
provided that the input signals on the analog inputs are more
positive than –30 mV. By taking the VSS pin negative, the part
can convert signals down to –VREF on its inputs. The AD7710
thus performs all signal conditioning and conversion for a singleor dual-channel system.
2. The AD7710 is ideal for microcontroller or DSP processor
applications with an on-chip control register that allows
control over filter cutoff, input gain, channel selection, signal
polarity, and calibration modes.
The AD7710 is ideal for use in smart, microcontroller based
systems. Input channel selection, gain settings, and signal polarity can be configured in software using the bidirectional serial
port. The AD7710 contains self-calibration, system calibration,
and background calibration options, and also allows the user to
read and write the on-chip calibration registers.
PRODUCT HIGHLIGHTS
1. The programmable gain front end allows the AD7710 to
accept input signals directly from a strain gage or transducer,
removing a considerable amount of signal conditioning.
3. The AD7710 allows the user to read and write the on-chip
calibration registers. This means that the microcontroller has
much greater control over the calibration procedure.
4. No missing codes ensures true, usable, 23-bit dynamic range
coupled with excellent ± 0.0015% accuracy. The effects of
temperature drift are eliminated by on-chip self-calibration,
which removes zero-scale and full-scale errors.
REV. G
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.
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
© 2004 Analog Devices, Inc. All rights reserved.
