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LTC1966 Precision Micropower RMS-to-DC Converter FeaTures
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DescripTion
The LTC(R)1966 is a true RMS-to-DC converter that utilizes an innovative patented DS computational technique. The internal delta sigma circuitry of the LTC1966 makes it simpler to use, more accurate, lower power and dramatically more flexible than conventional log antilog RMS-to-DC converters. The LTC1966 accepts single-ended or differential input signals (for EMI/RFI rejection) and supports crest factors up to 4. Common mode input range is rail-to-rail. Differential input range is 1VPEAK, and offers unprecedented linearity. Unlike previously available RMS-to-DC converters, the superior linearity of the LTC1966 allows hassle free system calibration at any input voltage. The LTC1966 also has a rail-to-rail output with a separate output reference pin providing flexible level shifting. The LTC1966 operates on a single power supply from 2.7V to 5.5V or dual supplies up to 5.5V. A low power shutdown mode reduces supply current to 0.5A. The LTC1966 is insensitive to PC board soldering and stresses, as well as operating temperature. The LTC1966 is packaged in the space saving MSOP package which is ideal for portable applications.
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Simple to Use, Requires One Capacitor True RMS DC Conversion Using DS Technology High Accuracy: 0.1% Gain Accuracy from 50Hz to 1kHz 0.25% Total Error from 50Hz to 1kHz High Linearity: 0.02% Linearity Allows Simple System Calibration Low Supply Current: 155A Typ, 170A Max Ultralow Shutdown Current: 0.1A Constant Bandwidth: Independent of Input Voltage 800kHz -3dB, 6kHz 1% Flexible Supplies: 2.7V to 5.5V Single Supply Up to 5.5V Dual Supply Flexible Inputs: Differential or Single-Ended Rail-to-Rail Common Mode Voltage Range Up to 1VPEAK Differential Voltage Flexible Output: Rail-to-Rail Output Separate Output Reference Pin Allows Level Shifting Wide Temperature Range: -55C to 125C Small Size: Space Saving 8-Pin MSOP Package
applicaTions
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True RMS Digital Multimeters and Panel Meters True RMS AC + DC Measurements
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and No Latency DS is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents including 6359576, 6362677, 6516291 and 6651036.
LINEARITY ERROR (VOUT mV DC - VIN mV ACRMS)
Typical applicaTion
Single Supply RMS-to-DC Converter
2.7V TO 5.5V VDD DIFFERENTIAL INPUT 0.1F OPT. AC COUPLING IN1 IN2 EN OUTPUT LTC1966 OUT RTN VSS GND CAVE 1F
1966 TA01
Quantum Leap in Linearity Performance
0.2 0 LTC1966,
-0.2 -0.4 -0.6 -0.8 -1.0 60Hz SINEWAVES 0 50 100 150 200 250 300 350 400 450 500 VIN (mV ACRMS) 1966 TA01b CONVENTIONAL LOG/ANTILOG
+ VOUT -
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LTC1966 absoluTe MaxiMuM raTings
(Note 1)
pin conFiguraTion
Supply Voltage VDD to GND ............................................. - 0.3V to 7V VDD to VSS ............................................ -0.3V to 12V VSS to GND ............................................. -7V to 0.3V Input Currents (Note 2) ...................................... 10mA Output Current (Note 3) ..................................... 10mA ENABLE Voltage ....................... VSS - 0.3V to VSS + 12V OUT RTN Voltage ............................... VSS - 0.3V to VDD Operating Temperature Range (Note 4) LTC1966C/LTC1966I ............................-40C to 85C LTC1966H .......................................... -40C to 125C LTC1966MP ....................................... -55C to 125C Specified Temperature Range (Note 5) LTC1966C/LTC1966I ............................-40C to 85C LTC1966H .......................................... -40C to 125C LTC1966MP ....................................... -55C to 125C Maximum Junction Temperature ......................... 150C Storage Temperature Range ................. -65C to 150C Lead Temperature (Soldering, 10 sec).................. 300C
TOP VIEW GND IN1 IN2 VSS 1 2 3 4 8 7 6 5 ENABLE VDD OUT RTN VOUT
MS8 PACKAGE 8-LEAD PLASTIC MSOP TJMAX = 150C, JA = 220C/W
orDer inForMaTion
LEAD FREE FINISH LTC1966CMS8#PBF LTC1966IMS8#PBF LTC1966HMS8#PBF LTC1966MPMS8#PBF TAPE AND REEL LTC1966CMS8#TRPBF LTC1966IMS8#TRPBF LTC1966HMS8#TRPBF LTC1966MPMS8#TRPBF PART MARKING* LTTG LTTH LTTG LTTG PACKAGE DESCRIPTION 8-Lead Plastic MSOP 8-Lead Plastic MSOP 8-Lead Plastic MSOP 8-Lead Plastic MSOP TEMPERATURE RANGE 0C to 70C -40C to 85C -40C to 125C -55C to 125C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
elecTrical characTerisTics
SYMBOL PARAMETER Conversion Accuracy GERR VOOS LINERR Conversion Gain Error
The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VDD = 5V, VSS = - 5V, VOUTRTN = 0V, CAVE = 10F VIN = 200mVRMS, , VENABLE = 0.5V unless otherwise noted.
CONDITIONS 50Hz to 1kHz Input (Notes 6, 7) LTC1966C, LTC1966I LTC1966H, LTC1966MP (Notes 6, 7) LTC1966C, LTC1966I LTC1966H, LTC1966MP 50mV to 350mV (Notes 7, 8) MIN TYP 0.1
l l
MAX 0.3 0.4 0.7 0.2 0.4 0.6 0.15
UNITS % % % mV mV mV %
Output Offset Voltage
0.1
l l l
Linearity Error
0.02
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LTC1966 elecTrical characTerisTics
SYMBOL PARAMETER PSRR Power Supply Rejection
The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VDD = 5V, VSS = - 5V, VOUTRTN = 0V, CAVE = 10F VIN = 200mVRMS, , VENABLE = 0.5V unless otherwise noted.
CONDITIONS (Note 9) LTC1966C, LTC1966I LTC1966H, LTC1966MP (Notes 6, 7, 10)
l l l
MIN
TYP 0.02
MAX 0.15 0.20 0.3 0.8 1.0 2 30 VDD
UNITS %V %V %V mV mV mV mV V M M
VIOS
Input Offset Voltage
0.02
Accuracy vs Crest Factor (CF) CF = 4 CF = 5 Input Characteristics IVR ZIN CMRRI VIMAX VIMIN PSRRI Input Voltage Range Input Impedance Input Common Mode Rejection Maximum Input Swing Minimum RMS Input Power Supply Rejection VDD Supply (Note 9) VSS Supply (Note 9) (Note 14) Average, Differential (Note 12) Average, Common Mode (Note 12) (Note 13) Accuracy = 1% (Note 14)
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60Hz Fundamental, 200mVRMS (Note 11) 60Hz Fundamental, 200mVRMS (Note 11)
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-1 -20 VSS 8 100 7 1 1.05
200 5
V/V V mV V/V V/V V k k V/V V V
250 120 VSS 75 85 30 16 1.0 0.9 1.05 250 50 6 20 800
600 300 VDD 95 200
Output Characteristics OVR ZOUT CMRRO VOMAX PSRRO Output Voltage Range Output Impedance Output Common Mode Rejection Maximum Differential Output Swing Power Supply Rejection VENABLE = 0.5V (Note 12) VENABLE = 4.5V (Note 13) Accuracy = 2%, DC Input (Note 14)
l l l l
VDD Supply (Note 9) VSS Supply (Note 9) CAVE = 10F CAVE = 10F
l l
1000 500
V/V V/V kHz kHz kHz
Frequency Response f1P f10P f- 3dB VDD VSS IDD ISS IDDS ISSS IIH 1% Additional Error (Note 15) 10% Additional Error (Note 15) 3dB Frequency (Note 15) Positive Supply Voltage Negative Supply Voltage Positive Supply Current Negative Supply Current Supply Currents Supply Currents ENABLE Pin Current High (Note 16) IN1 = 20mV, IN2 = 0V IN1 = 200mV, IN2 = 0V IN1 = 20mV, IN2 = 0V VENABLE = 4.5V VENABLE = 4.5V LTC1966H, LTC1966MP VENABLE = 4.5V
l l l l
Power Supplies 2.7 -5.5 155 158 12 0.5 -1 -2 -0.3 -0.1 -0.05 5.5 0 170 20 10 V V A A A A A A A
Shutdown Characteristics
l l l l
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LTC1966
The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VDD = 5V, VSS = - 5V, VOUTRTN = 0V, CAVE = 10F VIN = 200mVRMS, , VENABLE = 0.5V unless otherwise noted.
SYMBOL PARAMETER IIL VTH VHYS ENABLE Pin Current Low ENABLE Threshold Voltage CONDITIONS VENABLE = 0.5V LTC1966H, LTC1966MP VDD = 5V, VSS = -5V VDD = 5V, VSS = GND VDD = 2.7V, VSS = GND
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elecTrical characTerisTics
MIN -2 -10
TYP -1 2.4 2.1 1.3 0.1
MAX -0.1
UNITS A A V V V V
ENABLE Threshold Hysteresis
Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: The inputs (IN1, IN2) are protected by shunt diodes to VSS and VDD. If the inputs are driven beyond the rails, the current should be limited to less than 10mA. Note 3: The LTC1966 output (VOUT) is high impedance and can be overdriven, either sinking or sourcing current, to the limits stated. Note 4: The LTC1966C/LTC1966I are guaranteed functional over the operating temperature range of - 40C to 85C. The LTC1966H/ LTC1966MP are guaranteed functional over the operating temperature range of -55C to 125C. Note 5: The LTC1966C is guaranteed to meet specified performance from 0C to 70C. The LTC1966C is designed, characterized and expected to meet specified performance from -40C to 85C but is not tested nor QA sampled at these temperatures. The LTC1966I is guaranteed to meet specified performance from -40C to 85C. The LTC1966H is guaranteed to meet specified performance from -40C to 125C. The LTC1966MP is guaranteed to meet specified performance from -55C to 125C. Note 6: High speed automatic testing cannot be performed with CAVE = 10F The LTC1966 is 100% tested with CAVE = 22nF Correlation . . tests have shown that the performance limits above can be guaranteed with the additional testing being performed to guarantee proper operation of all the internal circuitry. Note 7: High speed automatic testing cannot be performed with 60Hz inputs. The LTC1966 is 100% tested with DC and 10kHz input signals. Measurements with DC inputs from 50mV to 350mV are used to calculate the four parameters: GERR, VOOS, VIOS and linearity error. Correlation tests have shown that the performance limits above can be guaranteed with the additional testing being performed to guarantee proper operation of all internal circuitry. Note 8: The LTC1966 is inherently very linear. Unlike older log/antilog circuits, its behavior is the same with DC and AC inputs, and DC inputs are used for high speed testing. Note 9: The power supply rejections of the LTC1966 are measured with DC inputs from 50mV to 350mV. The change in accuracy from VDD = 2.7V to VDD = 5.5V with VSS = 0V is divided by 2.8V. The change in accuracy from VSS = 0V to VSS = -5.5V with VDD = 5.5V is divided by 5.5V. Note 10: Previous generation RMS-to-DC converters required nonlinear input stages as well as a nonlinear core. Some parts specify a DC reversal error, combining the effects of input nonlinearity and input offset voltage. The LTC1966 behavior is simpler to characterize and the input offset voltage is the only significant source of DC reversal error.
Note 11: High speed automatic testing cannot be performed with 60Hz inputs. The LTC1966 is 100% tested with DC stimulus. Correlation tests have shown that the performance limits above can be guaranteed with the additional testing being performed to verify proper operation of all internal circuitry. Note 12: The LTC1966 is a switched capacitor device and the input/ output impedance is an average impedance over many clock cycles. The input impedance will not necessarily lead to an attenuation of the input signal measured. Refer to the Applications Information section titled Input Impedance for more information. Note 13: The common mode rejection ratios of the LTC1966 are measured with DC inputs from 50mV to 350mV. The input CMRR is defined as the change in VIOS measured between input levels of VSS to VSS + 350mV and input levels of VDD - 350mV to VDD divided by VDD - VSS - 350mV. The output CMRR is defined as the change in VOOS measured with OUT RTN = VSS and OUT RTN = VDD - 350mV divided by VDD - VSS - 350mV. Note 14: Each input of the LTC1966 can withstand any voltage within the supply range. These inputs are protected with ESD diodes, so going beyond the supply voltages can damage the part if the absolute maximum current ratings are exceeded. Likewise for the output pins. The LTC1966 input and output voltage swings are limited by internal clipping. The maximum differential input of the LTC1966 (referred to as maximum input swing) is 1V. This applies to either input polarity, so it can be thought of as 1V. Because the differential input voltage gets processed by the LTC1966 with gain, it is subject to internal clipping. Exceeding the 1V maximum can, depending on the input crest factor, impact the accuracy of the output voltage, but does not damage the part. Fortunately, the LTC1966's topology is relatively tolerant of momentary internal clipping. The input clipping is tested with a crest factor of 2, while the output clipping is tested with a DC input. Note 15: The LTC1966 exploits oversampling and noise shaping to reduce the quantization noise of internal 1-bit analog-to-digital conversions. At higher input frequencies, increasingly large portions of this noise are aliased down to DC. Because the noise is shifted in frequency, it becomes a low frequency rumble and is only filtered at the expense of increasingly long settling times. The LTC1966 is inherently wideband, but the output accuracy is degraded by this aliased noise. These specifications apply with CAVE = 10F and constitute a 3-sigma variation of the output rumble. Note 16: The LTC1966 can operate down to 2.7V single supply but cannot operate at 2.7V. This additional constraint on VSS can be expressed mathematically as - 3 * (VDD - 2.7V) VSS Ground.
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LTC1966 Typical perForMance characTerisTics
Gain and Offsets vs Input Common Mode
0.5 0.4 0.3 GAIN ERROR (%) 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4 -0.5 -5 -4 -3 -2 -1 0 1 2 3 INPUT COMMON MODE (V) 4 5 GAIN ERROR VOOS VIOS VDD = 5V VSS = -5V 0.5 0.4 0.3 OFFSET VOLTAGE (mV) GAIN ERROR (%) 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4 -0.5 0.5 0.4 0.3 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4 -0.5 GAIN ERROR
Gain and Offsets vs Input Common Mode
VDD = 5V VSS = GND 0.5 VIOS VOOS 0.4 0.3 OFFSET VOLTAGE (mV) GAIN ERROR (%) 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4 -0.5 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 INPUT COMMON MODE (V)
1966 G02
Gain and Offsets vs Input Common Mode
0.5 0.4 0.3 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4 -0.5 0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 INPUT COMMON MODE (V)
1966 G01
VDD = 2.7V VSS = GND
1.0 0.8 VIOS GAIN ERROR 0.6 OFFSET VOLTAGE (mV) 0.4 0.2 0 VOOS -0.2 -0.4 -0.6 -0.8 -1.0
1966 G03
Gain and Offsets vs Output Common Mode
0.5 0.4 0.3 GAIN ERROR (%) 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4 -0.5 -5 -4 -3 -2 -1 0 1 2 3 OUTPUT COMMON MODE (V) 4 5 VIOS GAIN ERROR VOOS VDD = 5V VSS = -5V 0.5 0.4 0.3 OFFSET VOLTAGE (mV) GAIN ERROR (%) 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4 -0.5 0.5 0.4 0.3 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4 -0.5
Gain and Offsets vs Output Common Mode
VDD = 5V VSS = GND VIOS VOOS GAIN ERROR 0.5 0.4 0.3 OFFSET VOLTAGE (mV) GAIN ERROR (%) 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4 -0.5 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 OUTPUT COMMON MODE (V)
1966 G05
Gain and Offsets vs Output Common Mode
0.5 0.4 0.3 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4 -0.5 0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 OUTPUT COMMON MODE (V)
1966 G04
VDD = 2.7V VSS = GND
1.0 VIOS 0.8 0.6 OFFSET VOLTAGE (mV) 0.4 0.2 0
GAIN ERROR
VOOS
-0.2 -0.4 -0.6 -0.8 -1.0
1966 G06
Gain and Offsets vs Temperature
0.5 0.4 0.3 GAIN ERROR (%) 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4 VIOS GAIN ERROR VOOS VDD = 5V VSS = -5V 0.5 0.4 0.3 OFFSET VOLTAGE (mV) GAIN ERROR (%) 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4 0.5 0.4 0.3 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4
Gain and Offsets vs Temperature
VDD = 5V VSS = GND VIOS VOOS 0.5 0.4 0.3 OFFSET VOLTAGE (mV) GAIN ERROR (%) 0.2 0.1 0 GAIN ERROR -0.1 -0.2 -0.3 -0.4 0.5 0.4 0.3 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4
Gain and Offsets vs Temperature
VDD = 2.7V VSS = GND 1.0 0.8 VIOS GAIN ERROR 0.6 OFFSET VOLTAGE (mV) 0.4 0.2 0 VOOS -0.2 -0.4 -0.6 -0.8
-0.5 -0.5 -60 -40 -20 0 20 40 60 80 100 120 140 TEMPERATURE (C)
1966 G09
-0.5 -0.5 -60 -40 -20 0 20 40 60 80 100 120 140 TEMPERATURE (C)
1966 G08
-1.0 -0.5 -60 -40 -20 0 20 40 60 80 100 120 140 TEMPERATURE (C)
1966 G07
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LTC1966 Typical perForMance characTerisTics
Gain and Offsets vs VSS Supply
0.5 0.4 0.3 GAIN ERROR (%) 0.2 0.1 0 NOMINAL SPECIFIED CONDITIONS -0.1 -0.2 -0.3 -0.4 -0.5 -6 GAIN ERROR VOOS VIOS VDD = 5V 0.5 0.4 0.3 OFFSET VOLTAGE (mV) GAIN ERROR (%) 0.2 0.1 0 - 0.1 - 0.2 - 0.3 - 0.4 -4 -3 VSS (V) -2 -1 0
1966 G11
Gain and Offsets vs VDD Supply
0.5 0.4 0.3 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4 -0.5 2.5 3.0 3.5 4.0 VDD (V) 4.5 5.0 GAIN ERROR VOOS VSS = GND VIOS 1 0.8 OUTPUT VOLTAGE (mV DC) 0.6 OFFSET VOLTAGE (mV) 0.4 0.2 0 - 0.2 - 0.4 - 0.6 - 0.8 -1.0 5.5
1966 G10
Performance vs Crest Factor
201.0 200mVRMS SCR WAVEFORMS CAVE = 10F 200.8 VDD = 5V O.1%/DIV
200.6 20Hz 200.4 100Hz 200.2 200.0 199.8 1.0 60Hz
-5
-0.5
1.5
2.0
2.5 3.0 3.5 4.0 CREST FACTOR
4.5
5.0
1966 G15
Performance vs Large Crest Factors
230 220 OUTPUT VOLTAGE (mV DC) 210 200 190 180 170 200mVRMS SCR WAVEFORMS = 4.7F C 160 VAVE= 5V DD 5%/DIV 150 6 2 3 5 4 1 CREST FACTOR
1966 G12
AC Linearity
0.20 VOUT (mV DC) - VIN (mV ACRMS) 0.15 0.10 0.05 0 60Hz SINEWAVES CAVE = 1F VIN2 = GND 10 5 0 -5 -10 -15 -20 0 50 100 150 200 250 300 350 400 450 500 VIN1 (mV ACRMS)
1966 G13
Output Accuracy vs Signal Amplitude
1% ERROR AC INPUTS = 60Hz SINEWAVES VIN2 = GND
FUNDAMENTAL FREQUENCY 20Hz 60Hz
100Hz
250Hz
VOUT (mV DC) - VIN (mVRMS)
-0.05 -0.10 -0.15 -0.20
-1% ERROR
AC INPUT VDD = 5V DC INPUT VDD = 5V
AC INPUT VDD = 3V 0 0.5 1 1.5 VIN1 (VRMS) 2 2.5
1966 G24
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DC Linearity
0.10 CAVE = 1F 0.08 VIN2 = GND 0.06 SUPPLY CURRENT (A) VOUTDC - |VINDC| (mV) 0.04 0.02 0 -0.02 -0.04 -0.06 -0.08 -0.10 -500 -300 EFFECT OF OFFSETS MAY BE POSITIVE OR NEGATIVE 100 -100 VIN1 (mV) 300 500
1966 G14
Quiescent Supply Currents vs Supply Voltage
200 175 150 125 100 75 50 25 0 -25 0 1 ISS 2 5 3 4 VDD SUPPLY VOLTAGE (V) 6
1966 G16
Shutdown Currents vs ENABLE Voltage
250 200 SUPPLY CURRENT (A) 150 100 50 0 ISS IEN IDD VDD = 5V
VSS = GND IDD
500 250 0 -250 0 1 4 3 5 2 ENABLE PIN VOLTAGE (V) 6
1966 G18
ENABLE PIN CURRENT (nA)
-50 -100
-500
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LTC1966 Typical perForMance characTerisTics
Quiescent Supply Currents vs Temperature
170 160 150 140 IDD (A) 130 120 110 100 VDD = 5V, VSS = GND VDD = 5V, VSS = -5V VDD = 2.7V, VSS = GND VDD = 5V, VSS = -5V VDD = 5V, VSS = GND VDD = 2.7V, VSS = GND 40 35 OUTPUT DC VOLTAGE (mV) 30 25 ISS (A) 20 15 10 5 1 100 10K 100K 1K INPUT SIGNAL FREQUENCY (Hz) 1M
1966 G19
Input Signal Bandwidth
1000 0.1% ERROR 1% ERROR 10% ERROR -3dB OUTPUT DC VOLTAGE (mV) 202 200 198 196 194 192 190 188 186
Input Signal Bandwidth
100
10
0 90 - 60 -40 -20 0 20 40 60 80 100 120 140 TEMPERATURE (C)
1966 G17
184 1%/DIV CAVE = 2.2F 182 10 100 1 INPUT FREQUENCY (kHz)
1000
1966 G20
Bandwidth to 100kHz
202 201 OUTPUT DC VOLTAGE (mV) 200 VOUT (mV DC) 199 198 197 196 195 0 10 20 30 40 50 60 70 80 90 100 INPUT FREQUENCY (kHz)
1966 G21
DC Transfer Function Near Zero
30 25 20 15 10 5 0 -5 -10 -20 -15 -10 0 5 -5 VIN1 (mV DC) 10 15 20 COMMON MODE REJECTION RATIO (dB) VIN2 = GND THREE REPRESENTITIVE UNITS 110 100 90 80 70 60 50 40 30 20
Common Mode Rejection Ratio vs Frequency
VDD = 5V VSS = -5V 5V INPUT CONVERSION TO DC OUTPUT
0.5%/DIV CAVE = 47F
10
100
1k 10k FREQUENCY (Hz)
100k
1M
1966 G23
1966 G22
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LTC1966 pin FuncTions
GND (Pin 1): Ground. A power return pin. IN1 (Pin 2): Differential Input. DC coupled (polarity is irrelevant). IN2 (Pin 3): Differential Input. DC coupled (polarity is irrelevant). VSS (Pin 4): Negative Voltage Supply. GND to - 5.5V. VOUT (Pin 5): Output Voltage. This is high impedance. The RMS averaging is accomplished with a single shunt capacitor from this node to OUT RTN. The transfer function is given by: OUT RTN (Pin 6): Output Return. The output voltage is created relative to this pin. The VOUT and OUT RTN pins are not balanced and this pin should be tied to a low impedance, both AC and DC. Although it is typically tied to GND, it can be ti

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