19-0824; Rev 2; 3/96
True RMS-to-DC Converters
General Description
The MX536A and MX636 are true RMS-to-DC convert-
ers. They feature low power and are designed to accept
low-level input signals from 0 to 7V
RMS
for the MX536A
and 0 to 200mV
RMS
for the MX636. Both devices accept
complex input waveforms containing AC and DC com-
ponents. They can be operated from either a single sup-
ply or dual supplies. Both devices draw less than 1mA
of quiescent supply current, making them ideal for bat-
tery-powered applications.
Input and output offset, positive and negative waveform
symmetry (DC reversal), and full-scale accuracy are
laser trimmed, so that no external trims are required to
achieve full rated accuracy.
____________________________Features
o
True RMS-to-DC Conversion
o
Computes RMS of AC and DC Signals
o
Wide Response:
2MHz Bandwidth for V
RMS
> 1V (MX536A)
1MHz Bandwidth for V
RMS
> 100mV (MX636)
o
Auxiliary dB Output: 60dB Range (MX536A)
50dB Range (MX636)
o
Single- or Dual-Supply Operation
o
Low Power: 1.2mA typ (MX536A)
800µA typ (MX636)
MX536A/MX636
Ordering Information
PART
MX536AJC/D
MX536AJCWE
MX536AJD
MX536AJH
MX536AJN
MX536AJQ*
MX536AKCWE
MX536AKD
MX536AKH
MX536AKN
MX536AKQ*
MX536ASD
TEMP. RANGE
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
-55°C to +125°C
PIN-PACKAGE
Dice**
16 Wide SO
14 Ceramic
10 TO-100
14 Plastic DIP
14 CERDIP
16 Wide SO
14 Ceramic
10 TO-100
14 Plastic DIP
14 CERDIP
14 Ceramic
________________________Applications
Digital Multimeters
Battery-Powered Instruments
Panel Meters
Process Control
Pin Configurations
TOP VIEW
I
OUT
10
R
L
1
COMMON
2
+V
S
3
V
IN
4
9
BUF IN
8
BUF OUT
MX536A
MX636B
5
-V
S
7
dB
6
C
AV
Ordering Information continued at end of data sheet.
*
Maxim reserves the right to ship ceramic packages in lieu of
CERDIP packages.
**
Dice are specified at T
A
= +25°C.
_________Typical Operating Circuits
C
AV
TO-100
V
IN
1
N.C. 2
-V
S
3
C
AV
4
dB 5
BUF OUT 6
BUF IN 7
14 +V
S
13 N.C.
12 N.C.
V
IN
1
2
ABSOLUTE
VALUE
SQUARER
DIVIDER
14
13
12
11
+V
S
-V
S
MX536A
MX636
3
4
5
11 N.C.
10 COMMON
9
8
R
L
I
OUT
V
OUT
CURRENT
MIRROR
10
9
6
7
BUF
8
DIP
Pin Configurations continued at end of data sheet.
Typical Operating Circuits continued at end of data sheet.
1
________________________________________________________________
Maxim Integrated Products
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 408-737-7600 ext. 3468.
True RMS-to-DC Converters
MX536A/MX636
ABSOLUTE MAXIMUM RATINGS
Supply Voltage: Dual Supplies (MX536A) ............................±18V
(MX636) .............................±12V
Single Supply (MX536A) ...........................+36V
(MX636) .............................+24V
Input Voltage (MX536A).......................................................±25V
(MX636) .........................................................±12V
Power Dissipation (Package)
Plastic DIP (derate 12mW/°C above +75°C) ...............450mW
Small Outline (derate 10mW/°C above +75°C)............400mW
Ceramic (derate 10mW/°C above +75°C) ...................500mW
TO-100 metal can (derate 7mW/°C above +75°C) ......450mW
Output Short-Circuit Duration ........................................Indefinite
Operating Temperature Ranges
Commercial (J, K) ...............................................0°C to +70°C
Military (S) ......................................................-55°C to +125°C
Storage Temperature Range .............................-55°C to +150°C
Lead Temperature (soldering, 10sec)................................300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS—MX536A
(T
A
= +25°C, +V
S
= +15V, -V
S
= -15V, unless otherwise noted.)
PARAMETER
Transfer Equation
Averaging Time Constant
CONVERSION ACCURACY
Total Error, Internal Trim (Note 1)
MX536AJ, AS
MX536AK
MX536AJ
Total Error vs. Temperature
T
MIN
to +70°C
+70°C to +125°C
Total Error vs. Supply
Total Error vs. DC Reversal
Total Error, External Trim
(Note 1)
MX536AJ, AS
MX536AK
MX536AJ, AS
MX536AK
Crest Factor 1 to 2
Additional Error
FREQUENCY RESPONSE
(Note 3)
Bandwidth for 1%
Additional Error (0.09dB)
V
IN
= 10mV
V
IN
= 100mV
V
IN
= 1V
V
IN
= 10mV
±3dB Bandwidth
V
IN
= 100mV
V
IN
= 1V
5
45
120
90
450
2.3
kHz
MHz
kHz
Crest Factor = 3
Crest Factor = 7
MX536AK
MX536AS
MX536AS
±5 ±0.5
±2 ±0.2
±0.1 ±0.01
±0.05 ±0.005
±0.1 ±0.005
±0.03 ±0.005
±0.1 ±0.01
±0.2
±0.1
±3 ±0.3
±2 ±0.1
Specified Accuracy
-0.1
-1.0
% of
Reading
mV ±% of
Reading/V
% of
Reading
mV ±% of
Reading
mV ±% of
Reading/°C
mV ±% of
Reading
Figure 3
CONDITIONS
MIN
TYP
25
MAX
UNITS
ms/µF C
AV
V
OUT
= [avg. (V
IN
)
2
]
1
/
2
ERROR vs. CREST FACTOR
(Note 2)
2
_______________________________________________________________________________________
True RMS-to-DC Converters
ELECTRICAL CHARACTERISTICS—MX536A (continued)
(T
A
= +25°C, +V
S
= +15V, -V
S
= -15V, unless otherwise noted.)
PARAMETER
INPUT CHARACTERISTICS
±15V Supplies
Continuous RMS Peak Transient
Input Signal Range
±5V Supplies
Continuous RMS Peak Transient
Safe Input
Input Resistance
Input Offset Voltage
OUTPUT CHARACTERISTICS
MX536AJ
T
A
= +25°C
Offset Voltage
MX536AK
MX536AS
T
A
= T
MIN
to T
MAX
Supply Voltage
Output Voltage Swing
Output Current
Short Circuit Current
Output Resistance
dB OUTPUT
MX536AJ
Error
Scale Factor
Scale Factor TC (Uncompensated)
I
REF
I
REF
Range
I
OUT
TERMINAL
I
OUT
Scale Factor
I
OUT
Scale Factor Tolerance
Output Resistance
Voltage Compliance
20
40
±10
25
-V
S
to
(+V
S
- 2.5)
±20
30
µA/V
RMS
%
kΩ
V
0dB = 1V
RMS
5
1
V
IN
= 7mV to 7V
RMS
,
0dB = 1V
RMS
MX536AK
MX536AS
±0.4
±0.2
±0.5
-3
0.33
20
80
100
±0.6
±0.3
±0.6
mV/dB
% of
Reading/°C
µA
µA
dB
±15V Supplies
±5V Supplies
Source
Sink
MX536AJ, AK
MX536AS
MX536AJ, AK
MX536AS
0 to 11
0 to 2
5
-130
20
0.5
±0.1
±0.2
12.5
±0.1
±0.2
±1
±0.5
±2
±1
±2
mV/°C
mV/V
V
mA
µA
mA
Ω
mV
MX536AJ, AS
MX536AK
All Supplies
13.33
16.7
0.8
0.5
0 to 7
±20
0 to 2
±7
±25
20.00
±2
±1
V
RMS
V
PK
V
RMS
V
PK
V
PK
kΩ
mV
CONDITIONS
MIN
TYP
MAX
UNITS
MX536A/MX636
3
_______________________________________________________________________________________
True RMS-to-DC Converters
MX536A/MX636
ELECTRICAL CHARACTERISTICS—MX536A (continued)
(T
A
= +25°C, +V
S
= +15V, -V
S
= -15V, unless otherwise noted.)
PARAMETER
BUFFER AMPLIFIER
Input and Output Voltage Range
Input Offset Voltage
Input Bias Current
Input Resistance
Output Current
Short-Circuit Current
Small-Signal Bandwidth
Slew Rate (Note 4)
Source
Sink
+5
-130
20
1
5
R
S
= 25kΩ
-V
S
to
(+V
S
- 2.5)
±0.5
20
10
8
CONDITIONS
MIN
TYP
MAX
UNITS
V
±4
300
mV
nA
Ω
mA
µA
mA
MHz
V/µs
ELECTRICAL CHARACTERISTICS—MX636
(T
A
= +25°C, +V
S
= +3V, -V
S
= -5V, unless otherwise noted.)
PARAMETER
Transfer Equation
Averaging Time Constant
CONVERSION ACCURACY
Total Error, Internal Trim
(Notes 5, 6)
Total Error vs. Temperature
(0°C to +70°C)
Total Error vs. Supply
Total Error vs. DC Reversal
Total Error, External Trim
(Note 5)
V
IN
= 200mV
MX636J
MX636K
Crest Factor 1 to 2
Additional Error
Crest Factor = 3
Crest Factor = 6
FREQUENCY RESPONSE
(Notes 6, 8)
Bandwidth for 1%
Additional Error (0.09dB)
V
IN
= 10mV
V
IN
= 100mV
V
IN
= 200mV
V
IN
= 10mV
±3dB Bandwidth
V
IN
= 100mV
V
IN
= 200mV
14
90
130
100
900
1.5
kHz
MHz
kHz
MX636J
MX636K
MX636J
MX636K
MX636J
MX636K
±0.5 ±1.0
±0.2 ±0.5
±0.1 ±0.01
±0.1 ±0.005
±0.1 ±0.01
±0.2
±0.1
±0.3 ±0.1
±0.1 ±0.1
Specified Accuracy
-0.2
-0.5
±% of
Reading
mV ±% of
Reading
mV ±% of
Reading/°C
mV ±% of
Reading/V
±% of
Reading
mV ±% of
Reading
Figure 3
CONDITIONS
MIN
TYP
25
MAX
UNITS
ms/µF C
AV
V
OUT
= [avg. (V
IN
)2]
1/2
ERROR vs. CREST FACTOR
(Note 3)
4
_______________________________________________________________________________________
True RMS-to-DC Converters
ELECTRICAL CHARACTERISTICS—MX636 (continued)
(T
A
= +25°C, +V
S
= +3V, -V
S
= -5V, unless otherwise noted.)
PARAMETER
INPUT CHARACTERISTICS
CONDITIONS
Continuous RMS, All Supplies
+3V, -5V Supplies
Peak Transient
±2.5V Supplies
±5V Supplies
All Supplies
5.33
MIN
TYP
0 to 200
±2.8
±2
±5
±12
6.7
8.00
±0.5
±0.2
±0.5
±0.2
±10
±0.1
0 to 1
0 to 1
8
MX636J
MX636K
1.4
10
±0.3
±0.1
-3
+0.33
-0.033
4
12
±0.5
±0.2
MAX
UNITS
mV
RMS
V
PK
V
PK
kΩ
mV
MX536A/MX636
Input Signal Range
Safe Input
Input Resistance
MX636J
MX636K
OUTPUT CHARACTERISTICS
(Note 5)
Input Offset Voltage
T
A
= +25°C
Offset Voltage
T
A
= T
MIN
to T
MAX
With Supply Voltage
+3V, -5V Supplies
±5V to ±16.5V Supplies
MX636J
MX636K
mV
µV/°C
mV/V
V
kΩ
Output Voltage Swing
Output Resistance
dB OUTPUT
Error
Scale Factor
Scale Factor Tempco
I
REF
I
REF
Range
I
OUT
TERMINAL
I
OUT
Scale Factor
I
OUT
Scale Factor Tolerance
Output Resistance
Voltage Compliance
BUFFER AMPLIFIER
Input and Output Voltage Range
Input Offset Voltage
Input Current
Input Resistance
Output Current
Short-Circuit Current
Small-Signal Bandwidth
Slew Rate (Note 9)
7mV
≤
V
IN
≤
300mV
dB
mV/dB
%/°C
dB/°C
µA
µA
µA/V
RMS
0dB = 1V
RMS
2
1
8
50
100
-20
8
±10
10
-V
S
to
(+V
S
- 2.0)
-V
S
to
(+V
S
- 2)
R
S
= 10kΩ
MX636J
MX636K
±0.8
±0.5
100
10
8
Source
Sink
+5
-130
20
1
5
±2
±1
300
+20
12
%
kΩ
V
V
mV
nA
Ω
mA
µA
mA
MHz
V/µs
_______________________________________________________________________________________
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