AD AD622 Low cost instrumentation amplifier Datasheet

FEATURES
Easy to use
Low cost solution
Higher performance than two or three op amp design
Unity gain with no external resistor
Optional gains with one external resistor
(Gain range: 2 to 1000)
Wide power supply range: ±2.6 V to ±15 V
Available in 8-lead PDIP and 8-lead SOIC_N packages
Low power, 1.5 mA maximum supply current
DC performance
0.15% gain accuracy: G = 1
125 µV maximum input offset voltage
1.0 µV/°C maximum input offset drift
5 nA maximum input bias current
66 dB minimum common-mode rejection ratio: G = 1
Noise
12 nV/√Hz @ 1 kHz input voltage noise
0.60 µV p-p noise: 0.1 Hz to 10 Hz, G = 10
AC characteristics
800 kHz bandwidth: G = 10
10 µs settling time to 0.1% @ G = 1 to 100
1.2 V/µs slew rate
APPLICATIONS
Transducer interface
Low cost thermocouple amplifier
Industrial process controls
Difference amplifier
Low cost data acquisition
PIN CONFIGURATION
RG 1
8
RG
–IN 2
7
+VS
+IN
3
6
OUTPUT
–VS 4
5
REF
AD622
00777-001
Data Sheet
Low Cost Instrumentation Amplifier
AD622
Figure 1. 8-Lead PDIP and 8-Lead SOIC_N
(N and R Suffixes)
GENERAL DESCRIPTION
The AD622 is a low cost, moderately accurate instrumentation
amplifier in the traditional pin configuration that requires only
one external resistor to set any gain between 2 and 1000. For a
gain of 1, no external resistor is required. The AD622 is a
complete difference or subtractor amplifier system that also
provides superior linearity and common-mode rejection by
incorporating precision laser-trimmed resistors.
The AD622 replaces low cost, discrete, two or three op amp
instrumentation amplifier designs and offers good commonmode rejection, superior linearity, temperature stability,
reliability, power, and board area consumption. The low cost of
the AD622 eliminates the need to design discrete
instrumentation amplifiers to meet stringent cost targets. While
providing a lower cost solution, it also provides performance
and space improvements.
Table 1. Next Generation Upgrades for AD622
Part
AD8221
AD8222
AD8226
AD8220
AD8228
AD8295
AD8421
Comment
Better specs at lower price
Dual channel or differential out
Low power, wide input range
JFET input
Best gain accuracy
+2 precision op amps or differential out
Low noise, better specs
Rev. E
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 that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113 ©1996–2012 Analog Devices, Inc. All rights reserved.
AD622* Product Page Quick Links
Last Content Update: 11/01/2016
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Documentation
Application Notes
• AN-1401: Instrumentation Amplifier Common-Mode
Range: The Diamond Plot
• AN-244: A User's Guide to I.C. Instrumentation Amplifiers
• AN-245: Instrumentation Amplifiers Solve Unusual Design
Problems
• AN-282: Fundamentals of Sampled Data Systems
• AN-589: Ways to Optimize the Performance of a
Difference Amplifier
• AN-671: Reducing RFI Rectification Errors in In-Amp
Circuits
Data Sheet
• AD622: Low Cost Instrumentation Amplifier Data Sheet
Technical Books
• A Designer's Guide to Instrumentation Amplifiers, 3rd
Edition, 2006
User Guides
• UG-261: Evaluation Boards for the AD62x, AD822x and
AD842x Series
Design Resources
•
•
•
•
AD622 Material Declaration
PCN-PDN Information
Quality And Reliability
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AD622
Data Sheet
TABLE OF CONTENTS
Features .............................................................................................. 1
Theory of Operation .........................................................................9
Applications ....................................................................................... 1
Make vs. Buy: A Typical Application Error Budget ..................9
Pin Configuration ............................................................................. 1
Gain Selection ................................................................................. 11
General Description ......................................................................... 1
Input and Output Offset Voltage .............................................. 11
Revision History ............................................................................... 2
Reference Terminal .................................................................... 11
Specifications..................................................................................... 3
Input Protection ......................................................................... 11
Absolute Maximum Ratings............................................................ 5
RF Interference ........................................................................... 12
Thermal Resistance ...................................................................... 5
Ground Returns for Input Bias Currents ................................ 12
ESD Caution .................................................................................. 5
Outline Dimensions ....................................................................... 13
Typical Performance Characteristics ............................................. 6
Ordering Guide .......................................................................... 14
REVISION HISTORY
6/12—Rev. D to Rev. E
Changes to General Description Section; Added Table 1 ........... 1
Changes to Theory of Operation Section and Figure 16............. 9
Changes to Table 5 .......................................................................... 10
Changes to Input Selection Section; Deleted Large Input
Voltages at Large Gains Section; Added Figure 18, Renumbered
Sequentially ..................................................................................... 11
Changes to Ordering Guide .......................................................... 14
8/07—Rev. C to Rev. D
Updated Format .................................................................. Universal
Added Thermal Resistance Section ............................................... 5
Added Figure 16................................................................................ 9
Added Large Input Voltages at Large Gains Section ................. 11
Replaced RF Interference Section ................................................ 11
Deleted Grounding Section .......................................................... 10
Deleted Figure 16............................................................................ 10
Changes to Ground Returns for Input Bias Currents Section .. 12
Updated Outline Dimensions ....................................................... 13
Changes to Ordering Guide .......................................................... 14
4/99—Rev. B to Rev. C
8/98—Rev. A to Rev. B
2/97—Rev. 0 to Rev. A
1/96—Revision 0: Initial Version
Rev. E | Page 2 of 16
Data Sheet
AD622
SPECIFICATIONS
TA = 25°C, VS = ±15 V, and RL = 2 kΩ typical, unless otherwise noted.
Table 2.
Parameter
GAIN
Gain Range
Gain Error 1
G=1
G = 10
G = 100
G = 1000
Nonlinearity
G = 1 to 1000
G = 1 to 100
Gain vs. Temperature
VOLTAGE OFFSET
Input Offset, VOSI
Average Temperature Coefficient
Output Offset, VOSO
Average Temperature Coefficient
Offset Referred to Input vs. Supply (PSR)
G=1
G = 10
G = 100
G = 1000
INPUT CURRENT
Input Bias Current
Average Temperature Coefficient
Input Offset Current
Average Temperature Coefficient
INPUT
Input Impedance
Differential
Common Mode
Input Voltage Range 2
Over Temperature
Conditions
G = 1 + (50.5 k/RG)
Typ
1
Max
Unit
1000
VOUT = ±10 V
0.05
0.2
0.2
0.2
VOUT = ±10 V
RL = 10 kΩ
RL = 2 kΩ
Gain = 1
Gain > 11
Total RTI Error = VOSI + VOSO/G
VS = ±5 V to ±15 V
VS = ±5 V to ±15 V
VS = ±5 V to ±15 V
VS = ±5 V to ±15 V
VS = ±5 V to ±15 V
0.15
0.50
0.50
0.50
%
%
%
%
10
−50
ppm
ppm
ppm/°C
ppm/°C
125
1.0
1500
15
µV
µV/°C
µV
µV/°C
10
10
60
600
80
95
110
110
100
120
140
140
2.0
3.0
0.7
2.0
dB
dB
dB
dB
5.0
2.5
10||2
10||2
VS = ±2.6 V to ±5 V
VS = ±5 V to ±18 V
Over Temperature
Common-Mode Rejection Ratio
DC to 60 Hz with 1 kΩ Source Imbalance
G=1
G = 10
G = 100
G = 1000
OUTPUT
Output Swing
Min
−VS + 1.9
−VS + 2.1
−VS + 1.9
−VS + 2.1
+VS – 1.2
+VS – 1.3
+VS – 1.4
+VS – 1.4
nA
pA/°C
nA
pA/°C
G Ω||pF
GΩ||pF
V
V
V
V
VCM = 0 V to ±10 V
66
86
103
103
RL = 10 kΩ
VS = ±2.6 V to ±5 V
Over Temperature
VS = ±5 V to ±18 V
Over Temperature
Short Current Circuit
78
98
118
118
−VS + 1.1
−VS + 1.4
−VS + 1.2
−VS + 1.6
+VS – 1.2
+VS – 1.3
+VS – 1.4
+VS – 1.5
±18
Rev. E | Page 3 of 16
dB
dB
dB
dB
V
V
V
V
mA
AD622
Parameter
DYNAMIC RESPONSE
Small Signal −3 dB Bandwidth
G=1
G = 10
G = 100
G = 1000
Slew Rate
Settling Time to 0.1%
G = 1 to 100
NOISE
Voltage Noise, 1 kHz
Input Voltage Noise, eni
Output Voltage Noise, eno
RTI, 0.1 Hz to 10 Hz
G=1
G = 10
G = 100
Current Noise
0.1 Hz to 10 Hz
REFERENCE INPUT
RIN
IIN
Voltage Range
Gain to Output
POWER SUPPLY
Operating Range 3
Quiescent Current
Over Temperature
TEMPERATURE RANGE
For Specified Performance
Data Sheet
Conditions
Min
Typ
Max
Unit
1000
800
120
12
1.2
kHz
kHz
kHz
kHz
V/µs
10
µs
12
72
nV/√Hz
nV/√Hz
4.0
0.6
0.3
100
10
µV p-p
µV p-p
µV p-p
fA/√Hz
pA p-p
10 V step
Total RTI Noise = √(e2ni) + (eno∕G)2
f = 1 kHz
20
50
VIN+, VREF = 0
−VS + 1.6
60
+VS – 1.6
kΩ
µA
V
±18
1.3
1.5
V
mA
mA
1 ± 0.0015
±2.6
VS = ±2.6 V to ±18 V
0.9
1.1
−40 to +85
Does not include effects of External Resistor RG.
One input grounded, G = 1.
3
Defined as the same supply range that is used to specify PSR.
1
2
Rev. E | Page 4 of 16
°C
Data Sheet
AD622
ABSOLUTE MAXIMUM RATINGS
THERMAL RESISTANCE
Table 3.
Parameter
Supply Voltage
Internal Power Dissipation1
Input Voltage (Common Mode)
Differential Input Voltage2
Output Short Circuit Duration
Storage Temperature Range
Operating Temperature Range
Lead Temperature (Soldering, 10 sec)
1
2
θJA is specified for the device in free air.
Rating
±18 V
650 mW
±VS
±25 V
Indefinite
−65°C to +125°C
−40°C to +85°C
300°C
Table 4. Thermal Resistance
Package Type
8-Lead PDIP (N-8)
8-Lead SOIC_N (R-8)
ESD CAUTION
Specification is for device in free air; see Table 4.
May be further restricted for gains greater than 14. See the Input Protection
section for more information.
Stresses above those listed under Absolute Maximum Ratings
may cause permanent 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.
Rev. E | Page 5 of 16
θJA
95
155
Unit
°C/W
°C/W
AD622
Data Sheet
TYPICAL PERFORMANCE CHARACTERISTICS
TA = 25°C, VS = ±15 V, RL = 2 kΩ, unless otherwise noted.
50
1000
SAMPLE SIZE = 191
VOLTAGE NOISE (nV/ Hz)
PERCENTAGE OF UNITS
40
30
20
GAIN = 1
100
GAIN = 10
10
GAIN = 100, 1000
10
–0.8
–0.4
0
0.4
0.8
1.2
OUTPUT OFFSET VOLTAGE (mV)
1
00777-002
0
–1.2
Figure 2. Typical Distribution of Output Offset Voltage
1
10
100
1k
10k
100k
FREQUENCY (Hz)
00777-005
GAIN = 1000
BW LIMIT
Figure 5. Voltage Noise Spectral Density vs. Frequency (G = 1 to 1000)
50
1000
SAMPLE SIZE = 383
CURRENT NOISE (fA/ Hz)
PERCENTAGE OF UNITS
40
30
20
100
60
80
100
120
10
00777-003
0
140
COMMON-MODE REJECTION RATIO (dB)
1
100
1000
FREQUENCY (Hz)
Figure 3. Typical Distribution of Common-Mode Rejection
Figure 6. Current Noise Spectral Density vs. Frequency
2.0
140
120
1.5
100
G = 1000
G = 100
CMR (dB)
G = 10
1.0
80
G=1
60
40
0.5
0
0
1
2
3
4
WARM-UP TIME (Minutes)
5
0
0.1
1
10
100
1k
10k
100k
1M
FREQUENCY (Hz)
Figure 4. Change in Input Offset Voltage vs. Warm-Up Time
Figure 7. CMR vs. Frequency, RTI, 0 kΩ to 1 kΩ Source Imbalance
Rev. E | Page 6 of 16
00777-007
20
00777-004
INPUT OFFSET VOLTAGE (µV)
10
00777-006
10
Data Sheet
AD622
30
180
VS = ±15V
G = 10
OUTPUT VOLTAGE SWING (V p-p)
160
POSITIVE PSR (dB)
140
120
G = 1000
100
G = 100
80
60
G = 10
20
10
40
10
100
1k
10k
100k
1M
FREQUENCY (Hz)
0
10
00777-008
1
100
1k
10k
LOAD RESISTANCE (Ω)
Figure 8. Positive PSR vs. Frequency, RTI (G = 1 to 1000)
00777-011
G=1
20
0.1
Figure 11. Output Voltage Swing vs. Load Resistance
20
180
160
15
SETTLING TIME (µs)
120
100
G = 1000
80
G = 100
60
10
G=1
1
10
100
1k
10k
100k
1M
FREQUENCY (Hz)
0
0
5
10
15
20
OUTPUT STEP SIZE (V)
Figure 9. Negative PSR vs. Frequency, RTI (G = 1 to 1000)
00777-012
G = 10
40
20
0.1
TO 0.1%
5
00777-009
NEGATIVE PSR (dB)
140
Figure 12. Settling Time vs. Step Size (G = 1)
1000
1000
SETTLING TIME (µs)
10
100
10
0.1
100
1k
10k
100k
FREQUENCY (Hz)
1M
10M
Figure 10. Gain vs. Frequency
1
1
10
100
GAIN
Figure 13. Settling Time to 0.1% vs. Gain, for a 10 V Step
Rev. E | Page 7 of 16
1000
00777-013
1
00777-010
GAIN (V/V)
100
AD622
Data Sheet
10kΩ
0.01%
INPUT
20V p-p
1kΩ
POT
10kΩ
0.1%
VOUT
100kΩ
0.1%
100
90
+VS
1kΩ
0.1%
100Ω
0.1%
G = 1000
2
2V
5.62kΩ
8
3
Figure 14. Gain Nonlinearity, G = 1, RL = 10 kΩ (20 µV = 2 ppm)
4
Figure 15. Settling Time Test Circuit
Rev. E | Page 8 of 16
6
5
–VS
00777-014
10µV
511Ω
51.1Ω
0%
AD622
G=1
G = 100 G = 10
10
7
1
00777-015
11kΩ
0.1%
Ø
Data Sheet
AD622
THEORY OF OPERATION
The AD622 is a monolithic instrumentation amplifier based on
a modification of the classic three op amp approach. Absolute
value trimming allows the user to program gain accurately (to
0.5% at G = 1000) with only one resistor. Monolithic construction
and laser wafer trimming allow the tight matching and tracking
of circuit components, thus insuring AD622 performance.
The value of RG also determines the transconductance of the
preamp stage. As RG is reduced for larger gains, the transconductance increases asymptotically to that of the input
transistors. This has the following three important advantages:
Input Transistor Q1 and Input Transistor Q2 provide a single
differential-pair bipolar input for high precision (see Figure 16).
Feedback through the Q1-A1-R1 loop and the Q2-A2-R2 loop
maintains constant collector current of the Q1 and Q2 input
devices, thereby impressing the input voltage across External
Gain-Setting Resistor RG. This creates a differential gain from the
inputs to the A1 and A2 outputs given by G = (R1 + R2)/RG + 1.
Unity-Gain Subtractor A3 removes any common-mode signal,
yielding a single-ended output referred to the REF pin potential.
•
•
•
The internal gain resistors, R1 and R2, are trimmed to an
absolute value of 25.25 kΩ, allowing the gain to be programmed
accurately with a single external resistor.
MAKE vs. BUY: A TYPICAL APPLICATION ERROR
BUDGET
+V S
VB
20µA
I1
A1
The AD622 offers cost and performance advantages over
discrete two op amp instrumentation amplifier designs along
with smaller size and fewer components. In a typical application
shown in Figure 17, a gain of 10 is required to receive and
amplify a 0 to 20 mA signal from the AD694 current transmitter.
The current is converted to a voltage in a 50 Ω shunt. In
applications where transmission is over long distances, line
impedance can be significant so that differential voltage
measurement is essential. Where there is no connection
between the ground returns of transmitter and receiver, there
must be a dc path from each input to ground, implemented in
this case using two 1 kΩ resistors. The error budget detailed in
Table 5 shows how to calculate the effect of various error
sources on circuit accuracy.
I2
20µA
A2
10kΩ
C2
C1
10kΩ
OUTPUT
A3
10kΩ
+V S
10kΩ
REF
+V S
R1
R2
Q1
Q2
R3
400Ω
+IN
R4
400Ω
RG
GAIN
SENSE
GAIN
SENSE
00777-022
–V S
Figure 16. Simplified Schematic of the AD622
+
RL2
10Ω
AD694
0 TO 20mA
TRANSMITTER
0 TO 20mA
1kΩ
1/2
LT1013
VIN
50Ω
RL2
10Ω
1kΩ
1kΩ
RG
5.62kΩ
AD622
REF
1/2
LT1013
–
1kΩ
9kΩ*
1kΩ*
1kΩ*
9kΩ*
*0.1% RESISTOR MATCH, 50ppm/°C TRACKING
0 TO 20mA CURRENT LOOP
WITH 50Ω SHUNT IMPEDANCE
AD622 MONOLITHIC INSTRUMENTATION
AMPLIFIER, G = 9.986
Figure 17. Make vs. Buy
Rev. E | Page 9 of 16
HOMEBREW IN-AMP, G = 10
00777-016
– IN
Open-loop gain is boosted for increasing programmed
gain, thus reducing gain-related errors.
The gain-bandwidth product (determined by C1, C2, and
the preamp transconductance) increases with programmed
gain, thus optimizing frequency response.
The input voltage noise is reduced to a value of 12 nV/√Hz,
determined mainly by the collector current and base
resistance of the input devices.
AD622
Data Sheet
The AD622 provides greater accuracy at lower cost. The higher
cost of the homebrew circuit is dominated in this case by the
matched resistor network. One could also realize a homebrew
design using cheaper discrete resistors that are either trimmed
or hand selected to give high common-mode rejection. This
level of common-mode rejection, however, degrades significantly
over temperature due to the drift mismatch of the discrete
resistors.
Note that for the homebrew circuit, the LT1013 specification for
noise has been multiplied by √2. This is because a two op amp
type instrumentation amplifier has two op amps at its inputs,
both contributing to the overall noise.
Table 5. Make vs. Buy Error Budget
AD622 Circuit Calculation
Homebrew Circuit Calculation
Total Error in ppm
Relative to 1 V FS
AD622
Homebrew
125 µV + 1500 µV/10
2.5 nA × 1 kΩ
86 dB→50 ppm × 0.5 V
800 µV × 2
15 nA × 1 kΩ
(0.1% Match × 0.5 V)/10 V
Total Absolute Error
275
2.5
25
302.5
1600
15
50
1665
DRIFT TO 85°C
Gain Drift, ppm/°C
Total RTI Offset Voltage, µV/°C
Input Offset Current, pA/°C
(50 ppm + 5 ppm) × 60°C
(1 µV/°C + 15 µV/°C /10) × 60°C
2 pA/°C × 1 kΩ × 60°C
(50 ppm)/°C × 60°C
9 µV/°C × 2 × 60°C
155 pA/°C × 1 kΩ × 60°C
Total Drift Error
3300
150
0.12
3450.12
3000
1080
9.3
4089.3
RESOLUTION
Gain Nonlinearity, ppm of Full Scale
Typ 0.1 Hz to 10 Hz Voltage Noise, µV p-p
10 ppm
0.6 µV p-p
20 ppm
0.55 µV p-p × √2
Total Resolution Error
Grand Total Error
10
0.6
10.6
3763
20
0.778
20.778
5775
Error Source
ABSOLUTE ACCURACY at TA = 25°C
Total RTI Offset Voltage, µV
Input Offset Current, nA
CMR, dB
Rev. E | Page 10 of 16
Data Sheet
AD622
GAIN SELECTION
The AD622 gain is resistor programmed by RG or, more
precisely, by whatever impedance appears between Pin 1 and
Pin 8. The AD622 is designed to offer gains as close as possible
to popular integer values using standard 1% resistors. Table 6
shows required values of RG for various gains. Note that for
G = 1, the RG pins are unconnected (RG = ∞). For any arbitrary
gain, RG can be calculated by using the formula
50.5 k Ω
INPUT PROTECTION
G −1
To minimize gain error, avoid high parasitic resistance in series
with RG. To minimize gain drift, RG should have a low temperature
coefficient less than 10 ppm/°C for the best performance.
Table 6. Required Values of Gain Resistors
Desired
Gain
2
5
10
20
33
40
50
65
100
200
500
1000
1% Std Table Value of RG, Ω
51.1 k
12.7 k
5.62 k
2.67 k
1.58 k
1.3 k
1.02 k
787
511
255
102
51.1
The reference terminal potential defines the zero output voltage
and is especially useful when the load does not share a precise
ground with the rest of the system. The reference terminal provides
a direct means of injecting a precise offset to the output, with an
allowable range of 2 V within the supply voltages. Parasitic
resistance should be kept to a minimum for optimum CMR.
The AD622 safely withstands an input current of ±60 mA for
several hours at room temperature. This is true for all gains and
power on and off, which is useful if the signal source and amplifier
are powered separately. For longer time periods, the input
current should not exceed 6 mA.
For input voltages beyond the supplies, a protection resistor should
be placed in series with each input to limit the current to 6 mA.
These can be the same resistors as those used in the RFI filter.
High values of resistance can impact the noise and AC CMRR
performance of the system. Low leakage diodes (such as the
BAV199) can be placed at the inputs to reduce the required
protection resistance.
Calculated
Gain
1.988
4.976
9.986
19.91
32.96
39.85
50.50
65.17
99.83
199.0
496.1
989.3
+SUPPLY
R
+IN
VOUT
AD622
R
INPUT AND OUTPUT OFFSET VOLTAGE
REF
–IN
The low errors of the AD622 are attributable to two sources:
input and output errors. The output error is divided by G when
referred to the input. In practice, the input errors dominate at
high gains and the output errors dominate at low gains. The
total VOS for a given gain is calculated as follows:
Total Error RTI = input error + (output error/G)
Total Error RTO = (input error × G) + output error
Rev. E | Page 11 of 16
–SUPPLY
00777-023
RG =
REFERENCE TERMINAL
Figure 18. Diode Protection for Voltages Beyond Supply
AD622
Data Sheet
RF INTERFERENCE
GROUND RETURNS FOR INPUT BIAS CURRENTS
RF rectification is often a problem when amplifiers are used in
applications where there are strong RF signals. The disturbance
may appear as a small dc offset voltage. High frequency signals
can be filtered with a low-pass, RC network placed at the input
of the instrumentation amplifier, as shown in Figure 19. In
addition, this RC input network also provides additional input
overload protection (see the Input Protection section).
Input bias currents are those currents necessary to bias the
input transistors of an amplifier. There must be a direct return
path for these currents; therefore, when amplifying floating
input sources such as transformers or ac-coupled sources, there
must be a dc path from each input to ground as shown in
Figure 20, Figure 21, and Figure 22. Refer to the Designer’s
Guide to Instrumentation Amplifiers (free from Analog Devices,
Inc.) for more information regarding in-amp applications.
+VS
0.1µF
AD622
RG
VOUT
AD622
8
REF
–IN
+IN
3
10µF
–VS
REF
+
TO POWER
SUPPLY
GROUND
Figure 20. Ground Returns for Bias Currents with Transformer Coupled Inputs
Figure 19. RFI Suppression Circuit for AD622 Series In-Amps
+VS
–IN
The filter limits the input signal bandwidth to the following
cutoff frequencies:
FilterFreqCM =
LOAD
4
–VS
0.1µF
FilterFreq DIFF =
VOUT
6
5
00777-018
CC
1nF
7
1
+IN
RG
2
2
7
1
RG
AD622
8
1
2π R(2C D + CC )
+IN
VOUT
6
5
3
LOAD
4
REF
–VS
1
2π RCC
TO POWER
SUPPLY
GROUND
00777-019
R
4.02kΩ
–IN
Figure 21. Ground Returns for Bias Currents with Thermocouple Inputs
where CD ≥ 10CC.
+VS
Figure 19 shows an example where the differential filter
frequency is approximately 400 Hz, and the common-mode
filter frequency is approximately 40 kHz. With this differential
filter in place and operating at gain of 1000, the typical dc offset
shift over a frequency range of 1 Hz to 20 MHz is less than 1.5 µV
RTI, and the RF signal rejection of the circuit is better than
71 dB. At a gain of 100, the dc offset shift is well below 1 mV
RTI, and RF rejection is greater than 70 dB.
The input resistors should be selected to be high enough to
isolate the sensor from the CC and C D capacitors but low
enough not to influence system noise. Mismatch between
R × CC at the positive input and R × CC at the negative input
degrades the CMRR of the AD622. Therefore, the CC capacitors
should be high precision types such as NPO/COG ceramics.
The tolerance of the CD capacitor is less critical.
Rev. E | Page 12 of 16
–IN
2
7
1
RG
AD622
8
+IN
100kΩ
100kΩ
3
VOUT
6
5
LOAD
4
REF
–VS
TO POWER
SUPPLY
GROUND
00777-020
CD
47nF
+VS
+
00777-017
CC
1nF
R
4.02kΩ
10µF
Figure 22. Ground Returns for Bias Currents with AC-Coupled Inputs
Data Sheet
AD622
OUTLINE DIMENSIONS
0.400 (10.16)
0.365 (9.27)
0.355 (9.02)
8
5
1
4
0.280 (7.11)
0.250 (6.35)
0.240 (6.10)
0.100 (2.54)
BSC
0.325 (8.26)
0.310 (7.87)
0.300 (7.62)
0.060 (1.52)
MAX
0.210 (5.33)
MAX
0.015
(0.38)
MIN
0.150 (3.81)
0.130 (3.30)
0.115 (2.92)
SEATING
PLANE
0.022 (0.56)
0.018 (0.46)
0.014 (0.36)
0.195 (4.95)
0.130 (3.30)
0.115 (2.92)
0.015 (0.38)
GAUGE
PLANE
0.014 (0.36)
0.010 (0.25)
0.008 (0.20)
0.430 (10.92)
MAX
0.005 (0.13)
MIN
0.070 (1.78)
0.060 (1.52)
0.045 (1.14)
070606-A
COMPLIANT TO JEDEC STANDARDS MS-001
CONTROLLING DIMENSIONS ARE IN INCHES; MILLIMETER DIMENSIONS
(IN PARENTHESES) ARE ROUNDED-OFF INCH EQUIVALENTS FOR
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN.
CORNER LEADS MAY BE CONFIGURED AS WHOLE OR HALF LEADS.
Figure 23. 8-Lead Plastic Dual In-Line Package [PDIP]
Narrow Body
(N-8)
Dimensions shown in inches and (millimeters)
5.00 (0.1968)
4.80 (0.1890)
1
5
6.20 (0.2441)
5.80 (0.2284)
4
1.27 (0.0500)
BSC
0.25 (0.0098)
0.10 (0.0040)
COPLANARITY
0.10
SEATING
PLANE
1.75 (0.0688)
1.35 (0.0532)
0.51 (0.0201)
0.31 (0.0122)
0.50 (0.0196)
0.25 (0.0099)
45°
8°
0°
0.25 (0.0098)
0.17 (0.0067)
1.27 (0.0500)
0.40 (0.0157)
COMPLIANT TO JEDEC STANDARDS MS-012-A A
CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS
(IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN.
Figure 24. 8-Lead Standard Small Outline Package [SOIC_N]
Narrow Body
(R-8)
Dimensions shown in millimeters and (inches)
Rev. E | Page 13 of 16
012407-A
8
4.00 (0.1574)
3.80 (0.1497)
AD622
Data Sheet
ORDERING GUIDE
Model 1
AD622ANZ
AD622AR
AD622AR-REEL
AD622AR-REEL7
AD622ARZ
AD622ARZ-RL
AD622ARZ-R7
1
Temperature Range
−40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
Package Description
8-Lead PDIP
8-Lead SOIC_N
8-Lead SOIC_N
8-Lead SOIC_N
8-Lead SOIC_N
8-Lead SOIC_N
8-Lead SOIC_N
Z = RoHS Compliant Part.
Rev. E | Page 14 of 16
Package Option
N-8
R-8
R-8
R-8
R-8
R-8
R-8
Data Sheet
AD622
NOTES
Rev. E | Page 15 of 16
AD622
Data Sheet
NOTES
©1996–2012 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D00777-0-6/12(E)
Rev. E | Page 16 of 16