EVAL-AD7730EB AD [Analog Devices], EVAL-AD7730EB Datasheet

EVAL-AD7730EB

Manufacturer Part Number

EVAL-AD7730EB

Description

Bridge Transducer ADC

Manufacturer

AD [Analog Devices]

Datasheet

1.EVAL-AD7730EB.pdf (52 pages)

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FASTStep is a trademark of Analog Devices, Inc.

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

which may result from its use. No license is granted by implication or

otherwise under any patent or patent rights of Analog Devices.

GENERAL DESCRIPTION

The AD7730 is a complete analog front end for weigh-scale and

pressure measurement applications. The device accepts low-

level signals directly from a transducer and outputs a serial

digital word. The input signal is applied to a proprietary pro-

grammable gain front end based around an analog modulator.

KEY FEATURES

Resolution of 230,000 Counts (Peak-to-Peak)

Offset Drift: 5 nV/ C

Gain Drift: 2 ppm/ C

Line Frequency Rejection: >150 dB

Buffered Differential Inputs

Programmable Filter Cutoffs

Specified for Drift Over Time

Operates with Reference Voltages of 1 V to 5 V

ADDITIONAL FEATURES

Two-Channel Programmable Gain Front End

On-Chip DAC for Offset/TARE Removal

FAST Step™ Mode

AC or DC Excitation

Single Supply Operation

APPLICATIONS

Weigh Scales

Pressure Measurement

AIN2(+)/D1

AIN2(–)/D0

AIN1(+)

AIN1(–)

VBIAS

ACX

MUX

EXCITATION

CLOCK

100nA

AGND

FUNCTIONAL BLOCK DIAGRAM

AGND

BUFFER

6-BIT

DAC

REF IN(–) REF IN(+)

REFERENCE DETECT

+/–

DGND

PGA

AND CONTROL LOGIC

SERIAL INTERFACE

MICROCONTROLLER

POL

CALIBRATION

The modulator output is processed by a low pass programmable

digital filter, allowing adjustment of filter cutoff, output rate and

settling time.

The part features two buffered differential programmable gain

analog inputs as well as a differential reference input. The part

operates from a single +5 V supply. It accepts four unipolar

analog input ranges: 0 mV to +10 mV, +20 mV, +40 mV and

+80 mV and four bipolar ranges: 10 mV, 20 mV, 40 mV

and 80 mV. The peak-to-peak resolution achievable directly

from the part is 1 in 230,000 counts. An on-chip 6-bit DAC

allows the removal of TARE voltages. Clock signals for synchro-

nizing ac excitation of the bridge are also provided.

The serial interface on the part can be configured for three-wire

operation and is compatible with microcontrollers and digital

signal processors. The AD7730 contains self-calibration and

system calibration options, and features an offset drift of less

than 5 nV/ C and a gain drift of less than 2 ppm/ C.

The AD7730 is available in a 24-pin plastic DIP, a 24-lead

SOIC and 24-lead TSSOP package. The AD7730L is available

in a 24-lead SOIC and 24-lead TSSOP package.

NOTE

The description of the functions and operation given in this data

sheet apply to both the AD7730 and AD7730L. Specifications

and performance parameters differ for the parts. Specifications

for the AD7730L are outlined in Appendix A.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.

Tel: 781/329-4700

Fax: 781/326-8703

MODULATOR

SIGMA-DELTA A/D CONVERTER

SIGMA-

DELTA

RDY

AD7730

PROGRAMMABLE

GENERATION

Bridge Transducer ADC

DIGITAL

FILTER

CLOCK

RESET

World Wide Web Site: http://www.analog.com

AD7730/AD7730L

MCLK IN

MCLK OUT

SCLK

DIN

STANDBY

SYNC

DOUT

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