Analog Devices AD737KR-REEL7, AD737KN, AD737JR-REEL7, AD737JR-REEL, AD737JR Datasheet

Low Cost, Low Power,

FULL

WAVE

RECTIFIER

INPUT

AMPLIFIER

RMS CORE

COM

+V

S

OUTPUT

C

AV

–V

S

POWER

DOWN

V

IN

C

C

8kV

AD737

BIAS

SECTION

8kV

8

7

6

5

1

2

3

4

a

True RMS-to-DC Converter

AD737*

FEATURES
COMPUTES

True RMS Value
Average Rectified Value
Absolute Value

PROVIDES

200 mV Full-Scale Input Range

(Larger Inputs with Input Attenuator)

Direct Interfacing with 3 1/2 Digit

CMOS A/D Converters

High Input Impedance of 10

12

⍀
Low Input Bias Current: 25 pA max
High Accuracy: ⴞ0.2 mV ⴞ0.3% of Reading
RMS Conversion with Signal Crest Factors Up to 5
Wide Power Supply Range: +2.8 V, –3.2 V to ⴞ16.5 V
Low Power: 160 ␮A max Supply Current
No External Trims Needed for Specified Accuracy
AD736—A General Purpose, Buffered Voltage

Output Version Also Available

PRODUCT DESCRIPTION

The AD737 is a low power, precision, monolithic true rms-to-dc
converter. It is laser trimmed to provide a maximum error of

±0.2 mV ±0.3% of reading with sine-wave inputs. Furthermore,

it maintains high accuracy while measuring a wide range of
input waveforms, including variable duty cycle pulses and triac
(phase) controlled sine waves. The low cost and small physical
size of this converter make it suitable for upgrading the per­formance of non-rms “precision rectifiers” in many applications.
Compared to these circuits, the AD737 offers higher accuracy at
equal or lower cost.

The AD737 can compute the rms value of both ac and dc input
voltages. It can also be operated ac coupled by adding one ex­ternal capacitor. In this mode, the AD737 can resolve input sig-

nal levels of 100 µV rms or less, despite variations in temperature

or supply voltage. High accuracy is also maintained for input
waveforms with crest factors of 1 to 3. In addition, crest factors

The AD737 allows the choice of two signal input terminals: a
high impedance (10

with high Z input attenuators and a low impedance (8 kΩ) input

which allows the measurement of 300 mV input levels, while
operating from the minimum power supply voltage of +2.8 V,
–3.2 V. The two inputs may be used either singly or differentially.

The AD737 achieves a 1% of reading error bandwidth exceed­ing 10 kHz for input amplitudes from 20 mV rms to 200 mV
rms while consuming only 0.72 mW.

The AD737 is available in four performance grades. The
AD737J and AD737K grades are rated over the commercial

temperature range of 0°C to +70°C. The AD737A and AD737B
grades are rated over the industrial temperature range of –40°C
to +85°C.

The AD737 is available in three low-cost, 8-lead packages: plas­tic DIP, plastic SO and hermetic cerdip.

as high as 5 can be measured (while introducing only 2.5%
additional error) at the 200 mV full-scale input level.

The AD737 has no output buffer amplifier, thereby significantly
reducing dc offset errors occuring at the output. This allows the
device to be highly compatible with high input impedance A/D
converters.

Requiring only 160 µA of power supply current, the AD737 is

optimized for use in portable multimeters and other battery
powered applications. This converter also provides a “power

PRODUCT HIGHLIGHTS

1. The AD737 is capable of computing the average rectified
value, absolute value or true rms value of various input
signals.

2. Only one external component, an averaging capacitor, is
required for the AD737 to perform true rms measurement.

3. The low power consumption of 0.72 mW makes the AD737
suitable for many battery powered applications.

down” feature which reduces the power supply standby current

to less than 30 µA.

*Protected under U.S. Patent Number 5,495,245.

REV. C

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.

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., 1999

FUNCTIONAL BLOCK DIAGRAM

12

Ω) FET input which will directly interface

(@ +25ⴗC, ⴞ5 V supplies, ac coupled with 1 kHz sine-wave input applied unless

AD737–SPECIFICATIONS

Model Conditions Min Typ Max Min Typ Max Units

TRANSFER FUNCTION

CONVERSION ACCURACY 1 kHz Sine Wave

Total Error, Internal Trim

All Grades 0–200 mV rms 0.2/0.3 0.4/0.5 0.2/0.2 0.2/0.3 ±mV/±% of Reading

T

MIN-TMAX

A&B Grades @ 200 mV rms 0.5/0.7 0.3/0.5 ±mV/±% of Reading
J&K Grades @ 200 mV rms 0.007 0.007 ±% of Reading/°C

vs. Supply Voltage

@ 200 mV rms Input V

@ 200 mV rms Input V
dc Reversal Error, dc Coupled @ 600 mV dc 1.3 2.5 1.3 2.5 % of Reading
Nonlinearity

2

, 0–200 mV @ 100 mV rms 0 +0.25 +0.35 0 +0.25 +0.35 % of Reading

Total Error, External Trim 0–200 mV rms 0.1/0.2 0.1/0.2 ±mV/±% of Reading

ERROR vs. CREST FACTOR

Crest Factor 1 to 3 CAV, C
Crest Factor = 5 CAV, C

INPUT CHARACTERISTICS

High Impedance Input (Pin 2)

Signal Range

Continuous rms Level V
Continuous rms Level V
Peak Transient Input V
Peak Transient Input V
Peak Transient Input V
Input Resistance 10
Input Bias Current V

Low Impedance Input (Pin 1)

Signal Range

Continuous rms Level V
Continuous rms Level V
Peak Transient Input V
Peak Transient Input V
Peak Transient Input V

Input Resistance 6.4 8 9.6 6.4 8 9.6 kΩ

Maximum Continuous

Nondestructive Input All Supply Voltages ±12 ±12 V p-p

Input Offset Voltage

J&K Grades ⴞ3 ⴞ3 mV

A&B Grades ⴞ3 ⴞ3 mV

vs. Temperature 8 30 8 30 µV/°C

vs. Supply V

vs. Supply V

OUTPUT CHARACTERISTICS

Output Voltage Swing

No Load V

No Load V

No Load V

Output Resistance @ dc 6.4 8 9.6 6.4 8 9.6 kΩ

FREQUENCY RESPONSE

High Impedance Input (Pin 2)

For 1% Additional Error Sine-Wave Input

V

= 1 mV rms 1 1 kHz

IN

V

= 10 mV rms 6 6 kHz

IN

V

= 100 mV rms 37 37 kHz

IN

V

= 200 mV rms 33 33 kHz

IN

±3 dB Bandwidth Sine-Wave Input

= 1 mV rms 5 5 kHz

V

IN

V

= 10 mV rms 55 55 kHz

IN

V

= 100 mV rms 170 170 kHz

IN

VIN = 200 mV rms 190 190 kHz

1

ac Coupled Using C

200 mV–1 V rms –1.2 ⴞ2.0 –1.2 ⴞ2.0 % of Reading

= ±5 V to ±16.5 V 0 +0.06 +0.1 0 +0.06 +0.1 %/V

S

= ±5 V to ±3 V 0 –0.18 –0.3 0 –0.18 –0.3 %/V

S

3

= 100 µF 0.7 0.7 % Additional Error

F

= 100 µF 2.5 2.5 % Additional Error

F

= +2.8 V, –3.2 V 200 200 mV rms

S

= ±5 V to ±16.5 V 11V rms

S

= +2.8 V, –3.2 V ⴞ0.9 ⴞ0.9 V

S

= ±5 V ±2.7 ±2.7 V

S

= ±16.5 V ⴞ4.0 ⴞ4.0 V

S

= ±5 V 1 25 1 25 pA

S

= +2.8 V, –3.2 V 300 300 mV rms

S

= ±5 V to ±16.5 V l l V rms

S

= +2.8 V, –3.2 V ±1.7 ±1.7 V

S

= ±5 V ±3.8 ±3.8 V

S

= ±16.5 V ±11 ±11 V

S

4

ac Coupled

= ±5 V to ±16.5 V 50 150 50 150 µV/V

S

= ±5 V to ±3 V 80 80 µV/V

S

= +2.8 V, –3.2 V 0 to –1.6 –1.7 0 to –1.6 –1.7 V

S

= ±5 V 0 to –3.3 –3.4 0 to –3.3 –3.4 V

S

= ±16.5 V 0 to –4 –5 0 to –4 –5 V

S

otherwise noted.)

AD737J/A AD737K/B

V

= Avg.(V

OUT

C

2

)

IN

12

V

OUT

= Avg.(V

10

2

)

IN

12

Ω

REV. C–2–

AD737J/A AD737K/B

FULL

WAVE

RECTIFIER

INPUT

AMPLIFIER

RMS CORE

COM

+V

S

OUTPUT

C

AV

–V

S

POWER

DOWN

V

IN

C

C

8kV

AD737

BIAS

SECTION

8kV

8

7

6

5

1

2

3

4

Model Conditions Min Typ Max Min Typ Max Units

FREQUENCY RESPONSE

Low Impedance Input (Pin 1)

For 1% Additional Error Sine-Wave Input

V

= 1 mV rms 1 1 kHz

IN

V

= 10 mV rms 6 6 kHz

IN

V

= 100 mV rms 90 90 kHz

IN

V

= 200 mV rms 90 90 kHz

IN

±3 dB Bandwidth Sine-Wave Input

= 1 mV rms 5 5 kHz

V

IN

V

= 10 mV rms 55 55 kHz

IN

V

= 100 mV rms 350 350 kHz

IN

VIN = 200 mV rms 460 460 kHz

POWER SUPPLY

Operating Voltage Range +2.8, –3.2 ±5 ±16.5 +2.8, –3.2 ±5 ±16.5 V
Quiescent Current Zero Signal 120 160 120 160 µA

V

= 200 mV rms, No Load Sine-Wave Input 170 210 170 210 µA

IN

Power Down Mode Current Pin 3 Tied to +V

S

25 40 25 40 µA

TEMPERATURE RANGE

Operating, Rated Performance

Commercial (0°C to +70°C) AD737J AD737K
Industrial (–40°C to +85°C) AD737A AD737B

NOTES

l

Accuracy is specified with the AD737 connected as shown in Figure 16 with capacitor CC.

2

Nonlinearity is defined as the maximum deviation (in percent error) from a straight line connecting the readings at 0 and 200 mV rms.

3

Error vs. Crest Factor is specified as additional error for a 200 mV rms signal. C.F. = V

4

DC offset does not limit ac resolution.

Specifications are subject to change without notice.

Specifications shown in boldface are tested on all production units at final electrical test. Results from those tests are used to calculate outgoing quality levels.

PEAK

/V rms.

AD737

ABSOLUTE MAXIMUM RATINGS

Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±16.5 V

Internal Power Dissipation

2

. . . . . . . . . . . . . . . . . . . . . 200 mW

1

Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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

Differential Input Voltage . . . . . . . . . . . . . . . . . . +V

and –V

S

S

Storage Temperature Range (Q) . . . . . . –65°C to +150°C

Storage Temperature Range (N, R) . . . . . –65°C to +125°C

Operating Temperature Range

AD737J/K . . . . . . . . . . . . . . . . . . . . . . . . . . . 0°C to +70°C

AD737A/B . . . . . . . . . . . . . . . . . . . . . . . . . .–40°C to +85°C

Lead Temperature Range (Soldering 60 sec) . . . . . . . . +300°C

ESD Rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .500 V

NOTES

1

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

Model Range Description Option

AD737AQ –40°C to +85°C Cerdip Q-8
AD737BQ –40°C to +85°C Cerdip Q-8
AD737JN 0°C to +70°C Plastic DIP N-8
AD737JR 0°C to +70°C SOIC SO-8
AD737JR-REEL 0°C to +70°C 13" Tape and Reel SO-8
AD737JR-REEL7 0°C to +70°C 7" Tape and Reel SO-8
AD737KN 0°C to +70°C Plastic DIP N-8
AD737KR 0°C to +70°C SOIC SO-8
AD737KR-REEL 0°C to +70°C 13" Tape and Reel SO-8
AD737KR-REEL7 0°C to +70°C 7" Tape and Reel SO-8

ORDERING GUIDE

Temperature Package Package

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

2

8-Lead Plastic DIP Package: θJA = 165°C/W
8-Lead Cerdip Package: θ

= 110°C/W

JA

Plastic DIP (N-8), Cerdip (Q-8), SOIC (SO-8)

PIN CONFIGURATIONS

8-Lead Small Outline Package: θJA = 155°C/W

REV. C –3–