Analog Devices AD536ASH, AD536ASE-883B, AD536ASD-883B, AD536ASD, AD536ASCHIPS Datasheet

REV. B

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a

AD536A

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

Integrated Circuit

True RMS-to-DC Converter

FEATURES
True RMS-to-DC Conversion
Laser-Trimmed to High Accuracy

0.2% Max Error (AD536AK)

0.5% Max Error (AD536AJ)

Wide Response Capability:

Computes RMS of AC and DC Signals
450 kHz Bandwidth: V rms > 100 mV
2 MHz Bandwidth: V rms > 1 V

Signal Crest Factor of 7 for 1% Error
dB Output with 60 dB Range
Low Power: 1.2 mA Quiescent Current
Single or Dual Supply Operation
Monolithic Integrated Circuit
–55ⴗC to +125ⴗC Operation (AD536AS)

PRODUCT DESCRIPTION

The AD536A is a complete monolithic integrated circuit which
performs true rms-to-dc conversion. It offers performance which
is comparable or superior to that of hybrid or modular units
costing much more. The AD536A directly computes the true
rms value of any complex input waveform containing ac and dc
components. It has a crest factor compensation scheme which
allows measurements with 1% error at crest factors up to 7. The
wide bandwidth of the device extends the measurement capabi­lity to 300 kHz with 3 dB error for signal levels above 100 mV.

An important feature of the AD536A not previously available in
rms converters is an auxiliary dB output. The logarithm of the
rms output signal is brought out to a separate pin to allow the
dB conversion, with a useful dynamic range of 60 dB. Using an
externally supplied reference current, the 0 dB level can be con­veniently set by the user to correspond to any input level from

0.1 to 2 volts rms.

The AD536A is laser trimmed at the wafer level for input and
output offset, positive and negative waveform symmetry (dc re­versal error), and full-scale accuracy at 7 V rms. As a result, no
external trims are required to achieve the rated unit accuracy.

There is full protection for both inputs and outputs. The input
circuitry can take overload voltages well beyond the supply lev­els. Loss of supply voltage with inputs connected will not cause
unit failure. The output is short-circuit protected.

The AD536A is available in two accuracy grades (J, K) for com­mercial temperature range (0°C to +70°C) applications, and one
grade (S) rated for the –55°C to +125°C extended range. The
AD536AK offers a maximum total error of ±2 mV ±0.2% of
reading, and the AD536AJ and AD536AS have maximum errors
of ±5 mV ± 0.5% of reading. All three versions are available in
either a hermetically sealed 14-lead DIP or 10-pin TO-100
metal can. The AD536AS is also available in a 20-leadless her­metically sealed ceramic chip carrier.

PRODUCT HIGHLIGHTS

1. The AD536A computes the true root-mean-square level of a
complex ac (or ac plus dc) input signal and gives an equiva­lent dc output level. The true rms value of a waveform is a
more useful quantity than the average rectified value since it
relates directly to the power of the signal. The rms value of a
statistical signal also relates to its standard deviation.

2. The crest factor of a waveform is the ratio of the peak signal
swing to the rms value. The crest factor compensation
scheme of the AD536A allows measurement of highly com­plex signals with wide dynamic range.

3. The only external component required to perform measure­ments to the fully specified accuracy is the capacitor which
sets the averaging period. The value of this capacitor determines
the low frequency ac accuracy, ripple level and settling time.

4. The AD536A will operate equally well from split supplies or
a single supply with total supply levels from 5 to 36 volts.
The one milliampere quiescent supply current makes the
device well-suited for a wide variety of remote controllers and
battery powered instruments.

5. The AD536A directly replaces the AD536 and provides im­proved bandwidth and temperature drift specifications.

PIN CONFIGURATIONS AND

FUNCTIONAL BLOCK DIAGRAMS

LCC (E-20A) Package

4

5

6

7

8

3 2 1 20 19

18

17

16

15

14

9 10 11 12 13

BUF

CURRENT

MIRROR

ABSOLUTE

VALUE

SQUARER

DIVIDER

25k⍀

25k⍀

AD536A

V

IN

NC

C

AV

dB

+V

S

NC

NC

NC

COM

R

L

I

OUT

NC = NO CONNECT

–V

S

BUF
OUT

BUF

IN

NC

NC

NC NC

NC

NC

TO-116 (D-14) and

Q-14 Package

14

13

12

11

10

9

8

1

2

3

4

5

6

7

ABSOLUTE

VALUE

CURRENT

MIRROR

25k⍀

25k⍀

BUF

SQUARER

DIVIDER

AD536A

NC = NO CONNECT

V

IN

NC

–V

S

C

AV

dB

BUF
OUT

BUF

IN

+V

S

NC

NC

NC

COM

R

L

I

OUT

TO-100 (H-10A)

Package

BUF

25k⍀

ABSOLUTE

VALUE

SQUARER

DIVIDER

CURRENT

MIRROR

25k⍀

AD536A

V

IN

C

AV

dB

+V

S

COM

R

L

I

OUT

–V

S

BUF
OUT

BUF IN

REV. B

–2–

AD536A–SPECIFICATIONS

Model AD536AJ AD536AK AD536AS

Min Typ Max Min Typ Max Min Typ Max Units

TRANSFER FUNCTION

V

OUT

= avg .(VIN)

2

V

OUT

= avg .(VIN)

2

V

OUT

= avg .(VIN)

2

CONVERSION ACCURACY

Total Error, Internal Trim1 (Figure 1) ⴞ5 ⴞ0.5 ⴞ2 ⴞ0.2 ⴞ5 ⴞ0.5 mV ± % of Reading

vs. Temperature, T

MIN

to +70°C ±0.1 ±0.01 ±0.05 ±0.005 ⴞ0.1 ⴞ0.005 mV ± % of Reading/°C

+70°C to +125°C ⴞ0.3 ⴞ0.005 mV ± % of Reading/°C

vs. Supply Voltage ±0.1 ±0.01 ±0.1 ±0.01 ±0.1 ±0.01 mV ± % of Reading/V
dc Reversal Error ±0.2 ±0.1 ±0.2 ± % of Reading

Total Error, External Trim1 (Figure 2) ±3 ±0.3 ±2 ±0.1 ±3 ±0.3 mV ± % of Reading

ERROR VS. CREST FACTOR

2

Crest Factor 1 to 2 Specified Accuracy Specified Accuracy Specified Accuracy
Crest Factor = 3 –0.1 –0.1 – 0.1 % of Reading
Crest Factor = 7 –1.0 –1.0 – 1.0 % of Reading

FREQUENCY RESPONSE

3

Bandwidth for 1% Additional Error (0.09 dB)

VIN = 10 mV 5 5 5 kHz
VIN = 100 mV 45 45 45 kHz
VIN = 1 V 120 120 120 kHz

±3 dB Bandwidth

VIN = 10 mV 90 90 90 kHz
VIN = 100 mV 450 450 450 kHz
VIN = 1 V 2.3 2.3 2.3 MHz

AVERAGlNG TlME CONSTANT (Figure 5) 25 25 25 ms/µF CAV

INPUT CHARACTERISTICS

Signal Range, ±15 V Supplies

Continuous rms Level 0 to 7 0 to 7 0 to 7 V rms
Peak Transient Input ±20 ±20 ± 20 V peak
Continuous rms Level, ±5 V Supplies 0 to 2 0 to 2 0 to 2 V rms
Peak Transient Input, ±5 V Supplies ±7 ±7 ±7 V peak

Maximum Continuous Nondestructive

Input Level (All Supply Voltages) ±25 ±25 ± 25 V peak
Input Resistance 13.33 16.67 20 13.33 16.67 20 13.33 16.67 20 kΩ
Input Offset Voltage 0.8 ±2 0.5 ± 1 0.8 ±2mV

OUTPUT CHARACTERISTICS

Offset Voltage, VIN = COM (Figure 1) ± 1 ±2 ± 0.5 ±1 ⴞ2 mV

vs. Temperature ±0.1 ±0.1 ⴞ0.2 mV/°C

vs. Supply Voltage ±0.1 ± 0.1 ± 0.2 mV/V
Voltage Swing, ±15 V Supplies 0 to +11 +12.5 0 to +11 +12.5 0 to +11 +12.5 V
±5 V Supply 0 to +2 0 to +2 0 to +2 V

dB OUTPUT (Figure 13)

Error, VlN 7 mV to 7 V rms, 0 dB = 1 V rms ±0.4 ⴞ0.6 ±0.2 ⴞ0.3 ±0.5 ⴞ0.6 dB
Scale Factor –3 –3 –3 mV/dB
Scale Factor TC (Uncompensated, see Fig-

ure 1 for Temperature Compensation) – 0.033 –0.033 –0.033 dB/°C

+0.33 +0.33 +0.33 % of Reading/°C

I

REF

for 0 dB = 1 V rms 5 20 80 5 20 80 5 20 80 µA

I

REF

Range 1 100 1 100 1 100 µA

I

OUT

TERMINAL

I

OUT

Scale Factor 40 40 40 µA/V rms

I

OUT

Scale Factor Tolerance ±10 ±20 ± 10 ± 20 ±10 ±20 %

Output Resistance 20 25 30 20 25 30 20 25 30 kΩ
Voltage Compliance –VS to (+V

S

–VS to (+V

S

–VS to (+V

S

–2.5 V) –2.5 V) –2.5 V) V

BUFFER AMPLIFIER

Input and Output Voltage Range –VS to (+V

S

–VS to (+V

S

–VS to (+V

S

V

–2.5 V) –2.5 V) –2.5 V)
Input Offset Voltage, RS = 25 k ±0.5 ⴞ4 ±0.5 ⴞ4 ± 0.5 ⴞ4 mV
Input Bias Current 20 60 20 60 20 60 nA
Input Resistance 10

8

10

8

10

8

Ω

Output Current (+5 mA, (+5 mA, (+5 mA,

–130 µA) –130 µA) –130 µA)
Short Circuit Current 20 20 20 mA
Output Resistance 0.5 0.5 0.5 Ω
Small Signal Bandwidth 1 1 1 MHz
Slew Rate

4

555V/µs

POWER SUPPLY

Voltage Rated Performance ± 15 ± 15 ± 15 V

Dual Supply ±3.0 ±18 ±3.0 ± 18 ± 3.0 ±18 V
Single Supply +5 +36 +5 +36 +5 +36 V

Quiescent Current

Total VS, 5 V to 36 V, T

MIN

to T

MAX

1.2 2 1.2 2 1.2 2 mA

TEMPERATURE RANGE

Rated Performance 0 +70 0 +70 –55 +125 °C
Storage –55 +150 –55 +150 –55 +150 °C

NUMBER OF TRANSISTORS 65 65 65

NOTES

1

Accuracy is specified for 0 V to 7 V rms, dc or 1 kHz sine wave input with the AD536A connected as in the figure referenced.

2

Error vs. crest factor is specified as an additional error for 1 V rms rectangular pulse input, pulsewidth = 200 µs.

3

Input voltages are expressed in volts rms, and error is percent of reading.

4

With 2k external pull-down resistor.

Specifications 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. All min and max specifications are guaranteed,

although only those shown in boldface are tested on all production units.

(@ +25ⴗC, and ⴞ15 V dc unless otherwise noted)

REV. B

AD536A

–3–

ABSOLUTE MAXIMUM RATINGS

1

Supply Voltage

Dual Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±18 V

Single Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +36 V

Internal Power Dissipation

2

. . . . . . . . . . . . . . . . . . . . 500 mW

Maximum Input Voltage . . . . . . . . . . . . . . . . . . . . ±25 V Peak

Buffer Maximum Input Voltage . . . . . . . . . . . . . . . . . . . . . ±V

S

Maximum Input Voltage . . . . . . . . . . . . . . . . . . . . ± 25 V Peak

Storage Temperature Range . . . . . . . . . . . . –55°C to +150°C

Operating Temperature Range

AD536AJ/K . . . . . . . . . . . . . . . . . . . . . . . . . . 0°C to +70°C

AD536AS . . . . . . . . . . . . . . . . . . . . . . . . –55°C to +125°C

Lead Temperature Range

(Soldering 60 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . +300°C

ESD Rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1000 V

NOTES

1

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 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

10-Pin Header: θJA = 150°C/W; 20-Leadless LCC: θJA = 95°C/W; 14-Lead Size

Brazed Ceramic DIP: θJA = 95°C/W.

CHIP DIMENSIONS AND PAD LAYOUT

Dimensions shown in inches and (mm).

ORDERING GUIDE

Temperature Package Package

Model Range Description Option

AD536AJD 0°C to +70°C Side Brazed Ceramic DIP D-14
AD536AKD 0°C to +70°C Side Brazed Ceramic DIP D-14
AD536AJH 0°C to +70°C Header H-10A
AD536AKH 0°C to +70°C Header H-10A
AD536AJQ 0°C to +70°C Cerdip Q-14
AD536AKQ 0°C to +70°C Cerdip Q-14
AD536ASD –55°C to +125°C Side Brazed Ceramic DIP D-14
AD536ASD/883B –55°C to +125°C Side Brazed Ceramic DIP D-14
AD536ASE/883B –55°C to +125°C LCC E-20A
AD536ASH –55°C to +125°C Header H-10A
AD536ASH/883B –55°C to +125°C Header H-10A
AD536AJCHIPS 0°C to +70°CDie
AD536AKH/+ 0°C to +70°C Header H-10A
AD536ASCHIPS –55°C to +125°CDie
5962-89805012A –55°C to +125°C LCC E-20A
5962-8980501CA –55°C to +125°C Side Brazed Ceramic DIP D-14
5962-8980501IA –55°C to +125°C Header H-10A

STANDARD CONNECTION

The AD536A is simple to connect for the majority of high accu­racy rms measurements, requiring only an external capacitor to
set the averaging time constant. The standard connection is
shown in Figure 1. In this configuration, the AD536A will mea­sure the rms of the ac and dc level present at the input, but will
show an error for low frequency inputs as a function of the filter
capacitor, C

AV

, as shown in Figure 5. Thus, if a 4 µF capacitor

is used, the additional average error at 10 Hz will be 0.1%, at
3 Hz it will be 1%. The accuracy at higher frequencies will be
according to specification. If it is desired to reject the dc input, a
capacitor is added in series with the input, as shown in Figure 3,
the capacitor must be nonpolar. If the AD536A is driven with
power supplies with a considerable amount of high frequency
ripple, it is advisable to bypass both supplies to ground with

0.1 µF ceramic discs as near the device as possible.

V

IN

+V

S

–V

S

V

OUT

C

AV

BUF

25k⍀

ABSOLUTE

VALUE

SQUARER

DIVIDER

CURRENT

MIRROR

25k⍀

AD536A

14

13

12

11

10

9

8

1

2

3

4

5

6

7

ABSOLUTE

VALUE

CURRENT

MIRROR

25k⍀

25k⍀

BUF

SQUARER

DIVIDER

AD536A

V

IN

–V

S

C

AV

+V

S

V

OUT

4

5

6

7

8

3 2 1 20 19

18

17

16

15

14

9 10 11 12 13

BUF

CURRENT

MIRROR

ABSOLUTE

VALUE

SQUARER

DIVIDER

25k⍀

25k⍀

AD536A

V

IN

+V

S

–V

S

V

OUT

C

AV

dB

Figure 1. Standard RMS Connection