ADT70 Analog Devices, ADT70 Datasheet

ADT70

Manufacturer Part Number

ADT70

Description

PRTD Conditioning Circuit And Temperature Controller

Manufacturer

Analog Devices

Datasheet

1.ADT70.pdf (14 pages)

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Part Number:

ADT70G

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GENERAL DESCRIPTION

The ADT70 provides excitation and signal conditioning for

resistance-temperature devices (RTDs). It is ideally suited for

1 k Platinum RTDs (PRTDs), allowing a very wide range of

temperature measurement. It can also easily interface to 100

PRTDs. Using a remote, low cost thin-film PRTD, the ADT70

can measure temperature in the range of –50 C to +500 C.

With high performance platinum elements, the temperature

change can be extended to 1000 C. Accuracy of the ADT70

and PRTD system over a –200 C to +1000 C temperature

range heavily depends on the quality of the PRTD. Typically

the ADT70 will introduce an error of only 1 C over the

transducer's temperature range, and the error may be trimmed

to zero at a single calibration point.

The ADT70 consists of two matched 1 mA (nominal) current

sources for transducer and reference resistor excitation, a preci-

sion rail-to-rail output instrumentation amplifier, a 2.5 V refer-

ence and an uncommitted rail-to-rail output op amp. The

ADT70 includes a shutdown function for battery powered

equipment, which reduces the quiescent current from 4 mA to

less than 10 A. The ADT70 operates from either single +5 V

or 5 V supplies. Gain or full-scale range for the PRTD and

ADT70 system is set by a precision external resistor connected

to the instrumentation amplifier. The uncommitted op amp may

be used for scaling the internal voltage reference, providing a

“PRTD open” signal or “over-temperature” warning, a heater

switching signal, or other external conditioning determined by

the user.

The ADT70 is specified for operation from 40 C to 125 C

and is available in 20-lead DIP and SO packages.

REV. 0

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.

Patent pending.

FEATURES

PRTD Temperature Measurement Range

Typical IC Measurement Error

Includes Two Matched Current Sources

Rail-to-Rail Output Instrumentation Amp

Uncommitted, Rail-to-Rail Output Op Amp

On-Board

Temperature Coefficient

Supply Current 4 mA Max

10 A Max in Shutdown

APPLICATIONS

Temperature Controllers

Portable Instrumentation

Temperature Acquisition Cards

5 V or

5 V Operation

2.5 V Reference

25 ppm/ C

1 C

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

Tel: 781/329-4700

Fax: 781/326-8703

+IN

OUTA

OUTB

NULLA

and Temperature Controller

RGA RGB

INST

AMP

PRTD Conditioning Circuit

FUNCTIONAL BLOCK DIAGRAM

SOURCES

MATCHED

CURRENT

NULLB

REFOUT

NULLA

NULLB

REFOUT

NULLA

NULLB

AGND

GND

SENSE

BIAS

OUTA

OUTB

–IN

+IN

BIAS

OUTA

OUTB

PIN CONFIGURATIONS

–V

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

BIAS 2.5V

20-Lead P-DIP

20-Lead SOIC

(Not to Scale)

TOP VIEW

OUT

TOP VIEW

(N Suffix)

(R Suffix)

ADT70

REFOUT

AGND

2.5V

REF

–IN

+IN

SHUTDOWN

DGND

GND SENSE

RGB

RGA

–IN

+IN

SHUTDOWN

DGND

GND SENSE

RGB

RGA

OUT OA

OUT IA

OUT OA

OUT IA

ADT70

DOWN

DGND

SHUT-

ADT70*

OUT

+IN

SHUTDOWN

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