AD622ANZ [ADI]

Low Cost Instrumentation Amplifier; 低成本仪表放大器
AD622ANZ
型号: AD622ANZ
厂家: ADI    ADI
描述:

Low Cost Instrumentation Amplifier
低成本仪表放大器

仪表放大器
文件: 总16页 (文件大小:394K)
中文:  中文翻译
下载:  下载PDF数据表文档文件
Low Cost Instrumentation Amplifier  
AD622  
FEATURES  
PIN CONFIGURATION  
R
1
2
3
4
Easy to use  
Low cost solution  
8
7
6
5
R
G
G
AD622  
–IN  
+IN  
+V  
S
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  
OUTPUT  
REF  
–V  
S
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 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 subtracter  
amplifier system that also provides superior linearity and  
common-mode rejection by incorporating precision laser-  
trimmed resistors.  
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  
The AD622 replaces low cost, discrete, two or three op amp  
instrumentation amplifier designs and offers good common-  
mode rejection, superior linearity, temperature stability,  
reliability, 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.  
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  
Rev. D  
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 registeredtrademarks arethe 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 ©1996–2007 Analog Devices, Inc. All rights reserved.  
 
AD622  
TABLE OF CONTENTS  
Features .............................................................................................. 1  
Theory of Operation .........................................................................9  
Make vs. Buy: A Typical Application Error Budget..................9  
Gain Selection................................................................................. 11  
Input and Output Offset Voltage.............................................. 11  
Reference Terminal .................................................................... 11  
Input Protection ......................................................................... 11  
RF Interference ........................................................................... 11  
Ground Returns for Input Bias Currents ................................ 12  
Outline Dimensions....................................................................... 13  
Ordering Guide .......................................................................... 14  
Applications....................................................................................... 1  
Pin Configuration............................................................................. 1  
General Description......................................................................... 1  
Revision History ............................................................................... 2  
Specifications..................................................................................... 3  
Absolute Maximum Ratings............................................................ 5  
Thermal Resistance ...................................................................... 5  
ESD Caution.................................................................................. 5  
Typical Performance Characteristics ............................................. 6  
REVISION HISTORY  
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. D | Page 2 of 16  
 
AD622  
SPECIFICATIONS  
TA = 25°C, VS = 15 V, and RL = 2 kΩ typical, unless otherwise noted.  
Table 1.  
Parameter  
Conditions  
Min  
Typ  
Max  
Unit  
GAIN  
G = 1 + (50.5 k/RG)  
Gain Range  
Gain Error1  
G = 1  
G = 10  
G = 100  
1
1000  
VOUT = 10 V  
0.05  
0.2  
0.2  
0.15  
0.50  
0.50  
0.50  
%
%
%
%
G = 1000  
Nonlinearity  
0.2  
VOUT = 10 V  
G = 1 to 1000  
G = 1 to 100  
RL = 10 kΩ  
RL = 2 kΩ  
10  
10  
ppm  
ppm  
Gain vs. Temperature  
Gain = 1  
Gain > 11  
10  
−50  
ppm/°C  
ppm/°C  
VOLTAGE OFFSET  
Input Offset, VOSI  
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  
60  
125  
1.0  
1500  
15  
μV  
μV/°C  
μV  
Average Temperature Coefficient  
Output Offset, VOSO  
Average Temperature Coefficient  
Offset Referred to Input vs. Supply (PSR)  
G = 1  
G = 10  
G = 100  
G = 1000  
600  
μV/°C  
80  
95  
110  
110  
100  
120  
140  
140  
dB  
dB  
dB  
dB  
INPUT CURRENT  
Input Bias Current  
Average Temperature Coefficient  
Input Offset Current  
Average Temperature Coefficient  
INPUT  
2.0  
3.0  
0.7  
2.0  
5.0  
2.5  
nA  
pA/°C  
nA  
pA/°C  
Input Impedance  
Differential  
Common Mode  
Input Voltage Range2  
10||2  
10||2  
G Ω||pF  
GΩ||pF  
V
V
V
V
VS = 2.6 V to 5 V  
VS = 5 V to 18 V  
VCM = 0 V to 10 V  
−VS + 1.9  
−VS + 2.1  
−VS + 1.9  
−VS + 2.1  
+VS – 1.2  
+VS – 1.3  
+VS – 1.4  
+VS – 1.4  
Over Temperature  
Over Temperature  
Common-Mode Rejection Ratio  
DC to 60 Hz with 1 kΩ Source Imbalance  
G = 1  
G = 10  
G = 100  
66  
86  
103  
103  
78  
98  
118  
118  
dB  
dB  
dB  
dB  
G = 1000  
OUTPUT  
Output Swing  
RL = 10 kΩ  
VS = 2.6 V to 5 V  
−VS + 1.1  
−VS + 1.4  
−VS + 1.2  
−VS + 1.6  
+VS – 1.2  
+VS – 1.3  
+VS – 1.4  
+VS – 1.5  
V
V
V
V
Over Temperature  
VS = 5 V to 18 V  
Over Temperature  
Short Current Circuit  
18  
mA  
Rev. D | Page 3 of 16  
 
 
AD622  
Parameter  
Conditions  
Min  
Typ  
Max  
Unit  
DYNAMIC RESPONSE  
Small Signal −3 dB Bandwidth  
G = 1  
G = 10  
G = 100  
G = 1000  
Slew Rate  
1000  
800  
120  
12  
kHz  
kHz  
kHz  
kHz  
V/μs  
1.2  
Settling Time to 0.1%  
G = 1 to 100  
10 V step  
10  
μs  
NOISE  
Voltage Noise, 1 kHz  
Input Voltage Noise, eni  
Output Voltage Noise, eno  
RTI, 0.1 Hz to 10 Hz  
G = 1  
Total RTI Noise = √(e2 ) + (eno⁄G)2  
ni  
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  
G = 10  
G = 100  
Current Noise  
0.1 Hz to 10 Hz  
REFERENCE INPUT  
RIN  
f = 1 kHz  
20  
50  
kΩ  
μA  
V
IIN  
VIN+, VREF = 0  
60  
+VS – 1.6  
Voltage Range  
Gain to Output  
POWER SUPPLY  
Operating Range3  
Quiescent Current  
Over Temperature  
TEMPERATURE RANGE  
For Specified Performance  
−VS + 1.6  
2.6  
1
0.0015  
18  
1.3  
1.5  
V
mA  
mA  
VS = 2.6 V to 18 V  
0.9  
1.1  
−40 to +85  
°C  
1 Does not include effects of External Resistor RG.  
2 One input grounded, G = 1.  
3 Defined as the same supply range that is used to specify PSR.  
Rev. D | Page 4 of 16  
 
 
 
AD622  
ABSOLUTE MAXIMUM RATINGS  
Table 2.  
THERMAL RESISTANCE  
θJA is specified for the device in free air.  
Parameter  
Rating  
Supply Voltage  
Internal Power Dissipation  
Input Voltage (Common Mode)  
Differential Input Voltage  
Output Short Circuit Duration  
Storage Temperature Range  
Operating Temperature Range  
Lead Temperature (Soldering, 10 sec)  
18 V  
650 mW  
VS  
Table 3. Thermal Resistance  
Package Type  
1
θJA  
Unit  
8-Lead PDIP (N-8)  
8-Lead SOIC_N (R-8)  
95  
155  
°C/W  
°C/W  
2
25 V  
Indefinite  
−65°C to +125°C  
−40°C to +85°C  
300°C  
ESD CAUTION  
1 Specification is for device in free air; see Table 3.  
2 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. D | Page 5 of 16  
 
 
 
 
AD622  
TYPICAL PERFORMANCE CHARACTERISTICS  
TA = 25°C, VS = 15 V, RL = 2 kΩ, unless otherwise noted.  
50  
1000  
100  
10  
SAMPLE SIZE = 191  
40  
30  
20  
10  
0
GAIN = 1  
GAIN = 10  
GAIN = 100, 1000  
GAIN = 1000  
BW LIMIT  
1
–1.2  
–0.8  
–0.4  
0
0.4  
0.8  
1.2  
1
10  
100  
1k  
10k  
100k  
OUTPUT OFFSET VOLTAGE (mV)  
FREQUENCY (Hz)  
Figure 2. Typical Distribution of Output Offset Voltage  
Figure 5. Voltage Noise Spectral Density vs. Frequency (G = 1 to 1000)  
50  
40  
30  
20  
10  
1000  
SAMPLE SIZE = 383  
100  
0
10  
60  
80  
100  
120  
140  
1
10  
100  
FREQUENCY (Hz)  
1000  
COMMON-MODE REJECTION RATIO (dB)  
Figure 3. Typical Distribution of Common-Mode Rejection  
Figure 6. Current Noise Spectral Density vs. Frequency  
2.0  
140  
120  
100  
80  
G = 1000  
G = 100  
G = 10  
1.5  
1.0  
0.5  
0
G = 1  
60  
40  
20  
0
0
1
2
3
4
5
0.1  
1
10  
100  
1k  
10k  
100k  
1M  
WARM-UP TIME (Minutes)  
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. D | Page 6 of 16  
 
AD622  
180  
160  
140  
120  
100  
80  
30  
20  
10  
0
V
= ±15V  
S
G = 10  
G = 1000  
G = 100  
60  
G = 10  
40  
G = 1  
20  
0.1  
1
10  
100  
1k  
10k  
100k  
1M  
10  
100  
1k  
10k  
FREQUENCY (Hz)  
LOAD RESISTANCE ()  
Figure 8. Positive PSR vs. Frequency, RTI (G = 1 to 1000)  
Figure 11. Output Voltage Swing vs. Load Resistance  
180  
160  
140  
120  
100  
80  
20  
15  
10  
5
TO 0.1%  
G = 1000  
G = 100  
60  
G = 10  
G = 1  
40  
0
20  
0.1  
1
10  
100  
1k  
10k  
100k  
1M  
0
5
10  
15  
20  
FREQUENCY (Hz)  
OUTPUT STEP SIZE (V)  
Figure 9. Negative PSR vs. Frequency, RTI (G = 1 to 1000)  
Figure 12. Settling Time vs. Step Size (G = 1)  
1000  
100  
10  
1000  
100  
10  
1
0.1  
1
100  
1k  
10k  
100k  
1M  
10M  
1
10  
100  
1000  
FREQUENCY (Hz)  
GAIN  
Figure 10. Gain vs. Frequency  
Figure 13. Settling Time to 0.1% vs. Gain, for a 10 V Step  
Rev. D | Page 7 of 16  
AD622  
10k  
1kΩ  
10kΩ  
0.1%  
0.01% POT  
INPUT  
20V p-p  
V
OUT  
100kΩ  
0.1%  
100  
90  
+V  
7
S
2
1
11kΩ  
0.1%  
1kΩ  
0.1%  
100Ω  
0.1%  
Ø
6
G = 1000  
G = 1  
G = 100 G = 10  
AD622  
8
5
3
10  
4
0%  
–V  
S
10µV  
2V  
Figure 14. Gain Nonlinearity, G = 1, RL = 10 kΩ (20 μV = 2 ppm)  
Figure 15. Settling Time Test Circuit  
Rev. D | Page 8 of 16  
AD622  
THEORY OF OPERATION  
The value of RG also determines the transconductance of the  
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 = 100) with only one resistor. Monolithic construction  
and laser wafer trimming allow the tight matching and tracking  
of circuit components, thus insuring AD622 performance.  
preamp stage. As RG is reduced for larger gains, the trans-  
conductance increases asymptotically to that of the input  
transistors. This has the following three important advantages:  
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.  
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 Subtracter 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  
20µA  
C1  
V
20µA  
I2  
I1  
B
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 4 shows how to calculate the effect of various error  
sources on circuit accuracy.  
A1  
A2  
10k  
C2  
10kΩ  
10kΩ  
A3  
OUTPUT  
REF  
10kΩ  
+IN  
R3  
R1  
R2  
400Ω  
–IN  
Q1  
Q2  
R4  
400Ω  
R
G
GAIN  
SENSE  
GAIN  
SENSE  
–V  
S
Figure 16. Simplified Schematic of the AD622  
+
R
L2  
1kΩ  
10Ω  
V
1/2  
LT1013  
IN  
1/2  
LT1013  
AD694  
0 TO 20mA  
TRANSMITTER  
0 TO 20mA  
50Ω  
1kΩ  
1kΩ  
R
G
5.62kΩ  
AD622  
1kΩ  
R
L2  
10Ω  
REF  
9k*  
1k*  
1k*  
9k*  
*0.1% RESISTOR MATCH, 50ppm/°C TRACKING  
HOMEBREW IN-AMP, G = 10  
0 TO 20mA CURRENT LOOP  
WITH 50SHUNT IMPEDANCE  
AD622 MONOLITHIC INSTRUMENTATION  
AMPLIFIER, G = 9.986  
Figure 17. Make vs. Buy  
Rev. D | Page 9 of 16  
 
 
 
AD622  
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 4. Make vs. Buy Error Budget  
Total Error in ppm  
Relative to 1 V FS  
Error Source  
AD622 Circuit Calculation  
Homebrew Circuit Calculation  
AD622  
Homebrew  
ABSOLUTE ACCURACY at TA = 25°C  
Total RTI Offset Voltage, μV  
Input Offset Current, nA  
CMR, dB  
250 μV + 1500 μV/10  
2.5 nA × 1 kΩ  
800 μV × 2  
15 nA × 1 kΩ  
(0.1% Match × 0.5 V)/10 V  
Total Absolute Error  
400  
2.5  
25  
1600  
15  
50  
86 dB50 ppm × 0.5 V  
427.5  
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  
(2 μV/°C + 15 μV/°C /10) × 60°C 9 μV/°C × 2 × 60°C  
2 pA/°C × 1 kΩ × 60°C  
(50 ppm)/°C × 60°C  
3300  
210  
0.12  
3000  
1080  
9.3  
155 pA/°C × 1 kΩ × 60°C  
Total Drift Error  
3510.12  
4089.3  
RESOLUTION  
Gain Nonlinearity, ppm of Full Scale  
Typ 0.1 Hz to 10 HzVoltage Noise, μV p-p  
10 ppm  
0.6 μV p-p  
20 ppm  
10  
0.6  
10.6  
3948  
20  
0.55 μV p-p × √2  
Total Resolution Error  
Grand Total Error  
0.778  
20.778  
5775  
Rev. D | Page 10 of 16  
 
AD622  
GAIN SELECTION  
separately. For longer time periods, the input current should not  
exceed 6 mA. For input overloads beyond the supplies, clamping  
the inputs to the supplies (using a diode such as a BAV199)  
reduces the required resistance, yielding lower noise.  
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 5  
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  
Large Input Voltages at Large Gains  
When operating at high gain, large differential input voltages  
may cause more than 6 mA of current to flow into the inputs.  
This condition occurs when the maximum differential voltage  
exceeds the following critical voltage:  
50.5 k Ω  
RG =  
G 1  
V
CRITICAL = (400 + RG) × (6 mA)  
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.  
This is true for differential voltages of either polarity.  
The maximum allowed differential voltage can be increased by  
adding an input protection resistor in series with each input.  
The value of each protection resistor should be as follows:  
Table 5. Required Values of Gain Resistors  
Desired  
Gain  
Calculated  
1% Std Table Value of RG, Ω Gain  
R
PROTECT = (VDIFF_MAX VCRITICAL)/6 mA  
2
5
10  
20  
33  
40  
50  
65  
100  
200  
500  
1000  
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  
1.988  
4.976  
9.986  
19.91  
32.96  
39.85  
50.50  
65.17  
99.83  
199.0  
496.1  
989.3  
RF INTERFERENCE  
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 18. In  
addition, this RC input network also provides additional input  
overload protection (see the Input Protection section).  
+V  
S
+
0.1µF  
+IN  
10µF  
C
1nF  
C
R
INPUT AND OUTPUT OFFSET VOLTAGE  
4.02k  
V
OUT  
C
D
47nF  
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:  
R
G
R
AD622  
4.02kΩ  
REF  
–IN  
C
C
1nF  
0.1µF  
10µF  
+
–V  
S
Total Error RTI = input error + (output error/G)  
Total Error RTO = (input error × G) + output error  
REFERENCE TERMINAL  
Figure 18. RFI Suppression Circuit for AD622 Series In-Amps  
The filter limits the input signal bandwidth to the following  
cutoff frequencies:  
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.  
1
FilterFreqDIFF  
=
2π R(2CD + CC )  
1
FilterFreqCM  
=
2π RCC  
INPUT PROTECTION  
where CD ≥ 10CC.  
The AD622 features 400 Ω of series thin film resistance at its  
inputs and safely withstands input overloads of up to 15 V or  
60 mA for up to an hour at room temperature. This is true for  
all gains and power on and off, which is particularly important  
because the signal source and amplifier can be powered  
Rev. D | Page 11 of 16  
 
 
 
 
 
 
 
AD622  
+V  
7
S
Figure 18 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.  
–IN  
+IN  
2
1
R
G
6
V
OUT  
AD622  
8
3
5
LOAD  
4
REF  
–V  
S
TO POWER  
SUPPLY  
GROUND  
The input resistors should be selected to be high enough to  
isolate the sensor from the CC and CD 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.  
Figure 19. Ground Returns for Bias Currents with Transformer Coupled Inputs  
+V  
S
–IN  
2
1
7
R
G
6
V
AD622  
OUT  
8
3
5
LOAD  
4
+IN  
REF  
GROUND RETURNS FOR INPUT BIAS CURRENTS  
–V  
S
TO POWER  
SUPPLY  
GROUND  
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 19, Figure 20, and Figure 21. Refer to the Designer’s  
Guide to Instrumentation Amplifiers (free from Analog Devices,  
Inc.) for more information regarding in-amp applications.  
Figure 20. Ground Returns for Bias Currents with Thermocouple Inputs  
+V  
S
–IN  
2
1
7
R
G
6
V
OUT  
AD622  
8
3
5
LOAD  
4
+IN  
REF  
100k  
100kΩ  
–V  
S
TO POWER  
SUPPLY  
GROUND  
Figure 21. Ground Returns for Bias Currents with AC-Coupled Inputs  
Rev. D | Page 12 of 16  
 
 
 
 
AD622  
OUTLINE DIMENSIONS  
0.400 (10.16)  
0.365 (9.27)  
0.355 (9.02)  
8
1
5
4
0.280 (7.11)  
0.250 (6.35)  
0.240 (6.10)  
0.325 (8.26)  
0.310 (7.87)  
0.300 (7.62)  
0.100 (2.54)  
BSC  
0.060 (1.52)  
MAX  
0.195 (4.95)  
0.130 (3.30)  
0.115 (2.92)  
0.210 (5.33)  
MAX  
0.015  
(0.38)  
MIN  
0.150 (3.81)  
0.130 (3.30)  
0.115 (2.92)  
0.015 (0.38)  
GAUGE  
0.014 (0.36)  
0.010 (0.25)  
0.008 (0.20)  
PLANE  
SEATING  
PLANE  
0.022 (0.56)  
0.018 (0.46)  
0.014 (0.36)  
0.430 (10.92)  
MAX  
0.005 (0.13)  
MIN  
0.070 (1.78)  
0.060 (1.52)  
0.045 (1.14)  
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 22. 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)  
8
1
5
4
6.20 (0.2441)  
5.80 (0.2284)  
4.00 (0.1574)  
3.80 (0.1497)  
0.50 (0.0196)  
0.25 (0.0099)  
1.27 (0.0500)  
BSC  
45°  
1.75 (0.0688)  
1.35 (0.0532)  
0.25 (0.0098)  
0.10 (0.0040)  
8°  
0°  
0.51 (0.0201)  
0.31 (0.0122)  
COPLANARITY  
0.10  
1.27 (0.0500)  
0.40 (0.0157)  
0.25 (0.0098)  
0.17 (0.0067)  
SEATING  
PLANE  
COMPLIANT TO JEDEC STANDARDS MS-012-AA  
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 23. 8-Lead Standard Small Outline Package [SOIC_N]  
Narrow Body  
(R-8)  
Dimensions shown in millimeters and (inches)  
Rev. D | Page 13 of 16  
 
AD622  
ORDERING GUIDE  
Model  
AD622AN  
AD622ANZ1  
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  
–40°C to +85°C  
Package Description  
8-Lead PDIP  
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  
Package Option  
N-8  
N-8  
R-8  
R-8  
R-8  
R-8  
R-8  
R-8  
AD622AR  
AD622AR-REEL  
AD622AR-REEL7  
AD622ARZ1  
AD622ARZ-RL1  
AD622ARZ-RL71  
1 Z = RoHS Compliant Part.  
Rev. D | Page 14 of 16  
 
 
 
 
 
 
AD622  
NOTES  
Rev. D | Page 15 of 16  
AD622  
NOTES  
©1996–2007 Analog Devices, Inc. All rights reserved. Trademarks and  
registered trademarks are the property of their respective owners.  
C00777-0-8/07(D)  
Rev. D | Page 16 of 16  
 
 

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