MX636JCWE ,True RMS-to-DC ConvertersGeneral Description ________
MX636JCWE ,True RMS-to-DC ConvertersFeatures' True RMS-to-DC ConversionThe MX536A and MX636 are true RMS-to-DC convert-ers. They featur ..
MX636JCWE+ ,True RMS-to-DC ConvertersApplicationsMX536AJCWE 0°C to +70°C 16 Wide SODigital MultimetersMX536AJD 0°C to +70°C 14 CeramicBa ..
MX636JH ,True RMS-to-DC ConvertersELECTRICAL CHARACTERISTICS—MX536A(T = +25°C, +V = +15V, -V = -15V, unless otherwise noted.)A S SPAR ..
MX636JN ,True RMS-to-DC Convertersapplications.' Low Power: 1.2mA typ (MX536A)Input and output offset, positive and negative waveform ..
MX636KCWE ,True RMS-to-DC ConvertersFeatures' True RMS-to-DC ConversionThe MX536A and MX636 are true RMS-to-DC convert-ers. They featur ..
NDP6051 ,N-Channel Enhancement Mode Field Effect TransistorElectrical Characteristics (T = 25°C unless otherwise noted)CSymbol Parameter Conditions Min Typ Ma ..
NDP6051 ,N-Channel Enhancement Mode Field Effect Transistorapplications. ________________________________________________________ ..
NDP605B ,N-Channel Enhancement Mode Power Fleid Effect TransistorElectrical Characteristics To = 25''C unless otherwise noted
Symbol TeatCondititms "mm Units
..
NDP6060 ,N-Channel Enhancement Mode Field Effect TransistorElectrical Characteristics (T = 25°C unless otherwise noted)CSymbol Parameter Conditions Min Typ Ma ..
NDP6060. ,N-Channel Enhancement Mode Field Effect TransistorElectrical Characteristics (T = 25°C unless otherwise noted)CSymbol Parameter Conditions Min Typ Ma ..
NDP6060L ,N-Channel Logic Level Enhancement Mode Field Effect TransistorFeaturesThese logic level N-Channel enhancement mode power 48A, 60V. R = 0.025Ω @ V = 5V. DS(ON) GS ..
MX536AJCWE-MX536AJD-MX536AJN-MX636JCWE-MX636JH-MX636JN-MX636KCWE-MX636KH
True RMS-to-DC Converters
General DescriptionThe 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 7VRMSfor the MX536A
and 0 to 200mVRMSfor 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.
________________________ApplicationsDigital Multimeters
Battery-Powered Instruments
Panel Meters
Process Control
____________________________FeaturesTrue RMS-to-DC ConversionComputes RMS of AC and DC SignalsWide Response:
2MHz Bandwidth for VRMS> 1V (MX536A)
1MHz Bandwidth for VRMS> 100mV (MX636)Auxiliary dB Output:60dB Range (MX536A)
50dB Range (MX636)Single- or Dual-Supply OperationLow Power:1.2mA typ (MX536A)
800µA typ (MX636)
MX536A/MX636rue RMS-to-DC Converters
Pin Configurations
_________Typical Operating Circuits19-0824; Rev 2; 3/96
MX536A/MX636
True RMS-to-DC Converters
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS—MX536A(TA= +25°C, +VS= +15V, -VS= -15V, unless otherwise noted.)
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.
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
MX536A/MX636rue RMS-to-DC Converters
ELECTRICAL CHARACTERISTICS—MX536A (continued)(TA= +25°C, +VS= +15V, -VS= -15V, unless otherwise noted.)
MX536A/MX636
True RMS-to-DC Converters
ELECTRICAL CHARACTERISTICS—MX536A (continued)(TA= +25°C, +VS= +15V, -VS= -15V, unless otherwise noted.)
ELECTRICAL CHARACTERISTICS—MX636(TA= +25°C, +VS= +3V, -VS= -5V, unless otherwise noted.)
MX536A/MX636rue RMS-to-DC Converters
ELECTRICAL CHARACTERISTICS—MX636 (continued)(TA= +25°C, +VS= +3V, -VS= -5V, unless otherwise noted.)
MX536A/MX636
_______________Detailed DescriptionThe MX536A/MX636 uses an implicit method of RMS
computation that overcomes the dynamic range as well
as other limitations inherent in a straightforward compu-
tation of the RMS. The actual computation performed
by the MX536A/MX636 follows the equation:
VRMS= Avg. [VIN2/VRMS]
The input voltage, VIN, applied to the MX536A/MX636 is
processed by an absolute-value/voltage to current con-
verter that produces a unipolar current I1(Figure 1).
This current drives one input of a squarer/divider that
produces a current I4that has a transfer function:= I12
The current I4drives the internal current mirror through
a lowpass filter formed by R1 and an external capaci-
tor, CAV. As long as the time constant of this filter is
greater than the longest period of the input signal, I4is
averaged. The current mirror returns a current, I3, to the
square/divider to complete the circuit. The current I4is
then a function of the average of (I12/I4), which is equal
to I1RMS.
The current mirror also produces a 2 · I4output current,
IOUT, that can be used directly or converted to a volt-
age using resistor R2 and the internal buffer to provide
a low-impedance voltage output. The transfer function
for the MX536A/MX636 is:
VOUT= 2 · R2 · IRMS= VIN
The dB output is obtained by the voltage at the emitter
of Q3, which is proportional to the -log VIN. The emitter
follower Q5 buffers and level shifts this voltage so that
the dB output is zero when the externally set emitter
current for Q5 approximates I3.
Standard Connection
(Figure 2)The standard RMS connection requires only one exter-
nal component, CAV. In this configuration the
MX536A/MX636 measures the RMS of the AC and DC
levels present at the input, but shows an error for low-
frequency inputs as a function of the CAVfilter capaci-
tor. Figure 3 gives practical values of CAVfor various
values of averaging error over frequency for the stan-
dard RMS connections (no post filtering). If a 3µF
capacitor is chosen, the additional error at 100Hz will
be 1%. If the DC error can be rejected, a capacitor
should be connected in series with the input, as would
typically be the case in single-supply operation.
The input and output signal ranges are a function of the
supply voltages. Refer to the electrical characteristics for
guaranteed performance. The buffer amplifier can be
used either for lowering the output impedance of the cir-
cuit, or for other applications such as buffering high-
impedance input signals. The MX536A/MX636 can be
used in current output mode by disconnecting the inter-
nal load resistor, RL, from ground. The current output is
available at pin 8 (pin 10 on the “H” package) with a
nominal scale of 40µA/VRMSinput for the MX536A and
100µA/VRMSinput for the MX636. The output is positive.
True RMS-to-DC Converters
ELECTRICAL CHARACTERISTICS—MX636 (continued)(TA= +25°C, +VS= +3V, -VS= -5V, unless otherwise noted.)
Note 1:Accuracy is specified for 0 to 7VRMS, DC or 1kHz sine-wave input with the MX536A connected as in Figure 2.
Note 2:Error vs. crest factor is specified as an additional error for 1VRMSrectangular pulse stream, pulse width = 200µs.
Note 3:Input voltages are expressed in volts RMS, and error as % of reading.
Note 4:With 2kΩexternal pull-down resistor.
Note 5:Accuracy is specified for 0 to 200mV, DC or 1kHz sine-wave input. Accuracy is degraded at higher RMS signal levels.
Note 6:Measured at pin 8 of DIP and SO (IOUT), with pin 9 tied to COMMON.
Note 7:Error vs. crest factor is specified as an additional error for 200mVRMSrectangular pulse input, pulse width = 200µs.
Note 8:Input voltages are expressed in volts RMS.
Note 9:With 10kΩexternal pull-down resistor from pin 6 (BUF OUT) to -VS.
Note 10:With BUF input tied to COMMON.
