Analog Devices ADT70 Datasheet

RGA RGB

ⴚIN

IA

+IN

IA

INST
AMP

SHUT­DOWN

GND
SENSE

OUTIAAGND DGNDⴚV

S

SHUTDOWN

+IN

OA

ⴚIN

OA

OUT

OA

+V

S

2.5V
REF

I

OUTA

I

OUTB

MATCHED
CURRENT
SOURCES

NULLA NULLB BIAS 2.5V

REFOUT

ADT70

PRTD Conditioning Circuit

a

GENERAL DESCRIPTION

The ADT70 provides excitation and signal conditioning for
resistance-temperature devices (RTDs). It is ideally suited for

1 kΩ Platinum RTDs (PRTDs), allowing a very wide range of
temperature measurement. It can also easily interface to 100 Ω

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 preci­sion rail-to-rail output instrumentation amplifier, a 2.5 V refer­ence 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␣ µA. 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 ⴚ40°C to ⴙ125°C

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

Patent pending.

*

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.

FEATURES
PRTD Temperature Measurement Range
Typical IC Measurement Error ⴞ1ⴗC
Includes Two Matched Current Sources
Rail-to-Rail Output Instrumentation Amp
Uncommitted, Rail-to-Rail Output Op Amp
On-Board ⴙ2.5 V Reference
Temperature Coefficient ⴞ25 ppm/ⴗC
ⴙ5 V or ⴞ5 V Operation
Supply Current 4 mA Max
10 ␮A Max in Shutdown

APPLICATIONS
Temperature Controllers
Portable Instrumentation
Temperature Acquisition Cards

and Temperature Controller

ADT70*

FUNCTIONAL BLOCK DIAGRAM

PIN CONFIGURATIONS

20-Lead P-DIP

(N Suffix)

–V

1

S

AGND

2

V

REFOUT

BIAS
NULLA
NULLB

I

OUTA

I

OUTB

–IN

+IN

3
4
5
6
7
8
9

IA

10

IA

ADT70

TOP VIEW

(Not to Scale)

a

20-Lead SOIC

(R Suffix)

–V

1

S

AGND

2

V

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone] World Wide Web Site: http://www.analog.com
Fax: [phone] © Analog Devices, Inc., 1998

REFOUT

BIAS
NULLA
NULLB

I

OUTA

I

OUTB

2 IN

1 IN

3
4
5
6
7
8
9

IA

10

IA

ADT70

TOP VIEW

(Not to Scale)

a

+V

20

V

19

OUT OA

–IN

18

+IN

17
16

SHUTDOWN

DGND

15

V

14

OUT IA

GND SENSE

13

RGB

12

RGA

11

+V

20

V

19

OUT OA

–IN

18

+IN

17
16

SHUTDOWN

DGND

15

V

14

OUT IA

GND SENSE

13

RGB

12

RGA

11

S

OA

OA

S

OA

OA

ADT70–SPECIFICATIONS

(V

= ⴙ5 V, ⴚ40ⴗC ≤ TA ≤ ⴙ125ⴗC unless otherwise noted)

S

Parameter Symbol Conditions Min Typ Max Units

SYSTEM CONFIGURATION

Gain R

= 1 kΩ 1.234 1.295 1.364 mV/Ω

L

Line Regulation –2.25 ⫾0.35 2.25 %/V

CURRENT SOURCES

Output Current I
Output Current Mismatch I

Q1

Q1

, I
– I

Q2

Q2

R

= 1 kΩ 0.9 mA

L

R

= 1 kΩ –2 ⫾0.5 2 µA

L

Voltage Compliance –VS to +VS – 1.5 V

INSTRUMENTATION AMP

Input Offset Voltage V

Output Offset Voltage V

Input Bias Current I

Input Offset Current I

IOS

OOS

B

OS

Common-Mode Rejection CMR V
Output Voltage Swing V

OUT

T

= +25°C –500 ⫾100 500 µV

A

= +25°C–7⫾37mV

T

A

T

= +25°C –60 ⫾30 60 nA

A

= 0.5 V to 3 V 65 85 dB

CM

RL = ∞ , VS = ⫾5 V –VS + 25 +VS – 25 mV

–700 ⫾150 700 µV

–12 ⫾512mV

–75 ⫾40 75 nA

–3 ⫾13nA

Power Supply Rejection Ratio PSRR + 4.5 V ≤ VS ≤ ⫾5.5 V –2.5 ⫾0.5 2.5 mV/V

VOLTAGE REFERENCE

Output Voltage 2.485 2.5 2.515 V

T

= +25°C 2.49 2.5 2.51 V

Load Regulation I

A

= 0 mA to 1 mA 250 ppm/mA

L

Temperature Coefficient ⫾10 ppm/°C
Line Regulation + 4.5 V ≤ VS ≤ +5.5 V ⫾75 ppm/V

OPERATIONAL AMPLIFIER

Input Offset Voltage V

Input Offset Voltage Drift T
Input Bias Current I

Input Offset Current I
Open-Loop Voltage Gain A
Output Voltage Swing V
Common-Mode Rejection Ratio CMRR V

IOA

CVIOA

B

OS

VOL

OUTA

T

= +25°C –800 ⫾200 800 µV

A

T

= +25°C –60 ⫾30 60 nA

A

RL =

∞

RL =

∞

= 1 V to 4 V 85 105 dB

CM

T

= +25°C 88 110 dB

A

Power Supply Rejection Ratio PSRR ⫾3 V ≤ V

Slew Rate SR T

= +25°C, AV = 1, 0.17 V/µs

A

≤ ⫾6 V 100 150 dB

S

–1,000 ⫾400 1,000 µV

1 µV/°C

–75 ⫾40 75 nA

–3 ⫾13nA

2V/µV

–VS + 10 +VS – 10 mV

VIN = 0 V to 4 V

SHUTDOWN INPUT

Input Low Voltage V
Input High Voltage V

IL

IH

2.4 V

0.8 V

POWER SUPPLY

Supply Current I
Shutdown Supply Current I
Supply Voltage V

SY

SD

S

R

= 1 kΩ 3.5 5 mA

L

10 30 µA

+4.5 +5.5 V

Dual Supply Voltage ⫾4.5 ⫾5.5 V

Specifications subject to change without notice.

REV. 0–2–

ADT70

WARNING!

ESD SENSITIVE DEVICE

ABSOLUTE MAXIMUM RATINGS*

ORDERING GUIDE

Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ⴙ16 V

Output Short-Circuit Duration . . . . . . . . . . . . . . . . . Indefinite

Storage Temperature Range

N, R Package . . . . . . . . . . . . . . . . . . . . . . ⴚ65°C to ⴙ150°C

Operating Temperature Range . . . . . . . . . . ⴚ40°C to ⴙ125°C

Junction Temperature Range

Model Range Package

ADT70GR ⴚ40°C to ⴙ125°C 20-Lead SOIC
ADT70GN ⴚ40°C to ⴙ125°C 20-Lead PDIP

Temperature

N, R Package . . . . . . . . . . . . . . . . . . . . . . ⴚ65°C to ⴙ125°C

Lead Temperature (Soldering, 60 sec) . . . . . . . . . . . . ⴙ300°C

NOTE
*Stresses above those listed under Absolute Maximum Ratings may cause perma-

nent damage to the device. This is a stress rating only; functional operation of the
device at these or any other conditions above those listed in the operational sections
of this specification is not implied. Exposure to absolute maximum rating condi­tions for extended periods may affect device reliability.

Package Type ␪

*

JA

␪

JC

Units

TRANSISTOR COUNT: 158

20-Lead SOIC (R) 74 24 °C/W
20-Lead PDIP (N) 102 31 °C/W

NOTE

*

θ

is specified for device in socket/soldered on circuit board (worst case conditions).

JA

CAUTION

ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily
accumulate on the human body and test equipment and can discharge without detection.
Although the ADT70 features proprietary ESD protection circuitry, permanent damage may
occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD
precautions are recommended to avoid performance degradation or loss of functionality.

REV. 0 –3–

ADT70

5

4.5 VS = +5V, NO LOAD
4

3.5

3

2.5

2

1.5

SUPPLY CURRENT – mA

1

0.5

0

225

25 75 125

TEMPERATURE – 8C

Figure 1. Supply Current vs. Temperature

1.4

VS = +5V, NO LOAD

1.35

1.3

SYSTEM GAIN – mV/V

1.25

1.2

225

25 75 125

TEMPERATURE – 8C

Figure 2. System Gain vs. Temperature

100

80

VS = +5V, NO LOAD
60

40

20

0

220

240

OFFSET VOLTAGE – mV

260

INSTRUMENTATION AMPLIFIER INPUT

280

2100

225

25 75 125

TEMPERATURE – 8C

Figure 4. Instrumentation Amplifier Input Offset Voltage
vs. Temperature

10

8

VS = +5V, NO LOAD

6

4

2

0

22

24

OFFSET VOLTAGE – mV

26

28

INSTRUMENTATION AMPLIFIER OUTPUT

210

225

25 75 125

TEMPERATURE – 8C

Figure 5. Instrumentation Amplifier Output Offset Voltage
vs. Temperature

0.1

0.08

VS = +5V, NO LOAD

0.06

0.04

0.02

0

20.02

20.04

SYSTEM GAIN PSRR – %/V

20.06

20.08

20.1
225

25 75 125

TEMPERATURE – 8C

Figure 3. Total System Gain PSRR vs. Temperature

0

VS = +5V, NO LOAD

210

220

230

240

BIAS CURRENT – nA

250

260

INSTRUMENTATION AMPLIFIER INPUT

270

225

25 75 125

TEMPERATURE – 8C

Figure 6. Instrumentation Amplifier Input Bias Current vs.
Temperature

REV. 0–4–

ADT70

500

400

VS = +5V, NO LOAD

300

200

100

0

2100

2200

OFFSET CURRENT – pA

2300

INSTRUMENTATION AMPLIFIER INPUT

2400
2500

225

25 75 125

TEMPERATURE – 8C

Figure 7. Instrumentation Amplifier Input Offset Current
vs. Temperature

1.6

VS = +5V, NO LOAD

1.55

1.5

0

VS = +5V, NO LOAD

210

220

230

240

250

OP AMP INPUT BIAS CURRENT – nA

260

270

225

25 75 125

TEMPERATURE – 8C

Figure 10. Op Amp Input Bias Current vs. Temperature

500

VS = +5V, NO LOAD

400

300

200

1.45

INSTRUMENTATION AMPLIFIER GAIN – V/V

1.4
225

25 75 125

TEMPERATURE – 8C

Figure 8. Instrumentation Amplifier Gain vs. Temperature

100

80

VS = +5V, NO LOAD

60

40

20

0

220

240

260

OP AMP INPUT OFFSET VOLTAGE – mV

280

2100

225

25 75 125

TEMPERATURE – 8C

Figure 9. Op Amp Input Offset Voltage vs. Temperature

100

OP AMP INPUT OFFSET CURRENT – pA

0

225

25 75 125

TEMPERATURE – 8C

Figure 11. Op Amp Input Offset Current vs. Temperature

2.51

VS = +5V, NO LOAD

2.505

2.5

2.495

REFERENCE VOLTAGE – V

2.49
225

25 75 125

TEMPERATURE – 8C

Figure 12. Reference Voltage vs. Temperature

REV. 0 –5–