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Dual, Low Power, Precision Rail-to-Rail Output Op Amp AD8622
FEATURES
Very low offset voltage 125 V maximum Supply current: 215 A/amp typical Input bias current: 200 pA maximum Low input offset voltage drift: 1.2 V/C maximum Very low voltage noise: 11 nV/Hz Operating temperature: -40C to +125C Rail-to-rail output swing Unity gain stable 2.5 V to 15 V operation
PIN CONFIGURATIONS
OUT A 1 -IN A 2 +IN A 3
8
V+ OUT B +IN B
07527-001
AD8622
7 6 5
TOP VIEW V- 4 (Not to Scale)
-IN B
Figure 1. 8-Lead Narrow-Body SOIC
OUT A 1 -IN A 2 +IN A 3 V- 4
8
AD8622
TOP VIEW (Not to Scale)
V+ OUT B +IN B
07527-002
7 6 5
-IN B
Figure 2. 8-Lead MSOP
APPLICATIONS
Portable precision instrumentation Laser diode control loops Strain gage amplifiers Medical instrumentation Thermocouple amplifiers
GENERAL DESCRIPTION
The AD8622 is a dual, precision rail-to-rail output operational amplifier with a low supply current of only 350 A maximum over temperature and supply voltages. It also offers ultralow offset, drift, and voltage noise combined with very low input bias current over the full operating temperature range. With typical offset voltage of only 10 V, offset drift of 0.5 V/C, and noise of only 0.2 V p-p (0.1 Hz to 10 Hz), it is perfectly suited for applications where large error sources cannot be tolerated. Many systems can take advantage of the low noise, dc precision, and rail-to-rail output swing provided by the AD8622 to maximize the signal-to-noise ratio and dynamic range for low power operation. The AD8622 is specified for the extended industrial temperature range of -40C to +125C and is available in lead-free SOIC and MSOP packages.
Table 1. Low Power Op Amps
Supply Single Dual 40 V OP97 OP297 36 V OP777 OP1177 OP727 OP2177 AD706 OP747 OP4177 AD704 12 V to 16 V OP196 AD8663 OP296 AD8667 OP496 AD8669 5V AD8603 AD8607
Quad
OP497
AD8609
Rev. 0
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 (c)2009 Analog Devices, Inc. All rights reserved.
AD8622 TABLE OF CONTENTS
Features .............................................................................................. 1 Applications ....................................................................................... 1 Pin Configurations ........................................................................... 1 General Description ......................................................................... 1 Revision History ............................................................................... 2 Specifications..................................................................................... 3 Electrical Characteristics--15 V Operation ........................... 3 Electrical Characteristics--2.5 V Operation .......................... 4 Absolute Maximum Ratings............................................................ 5 Thermal Resistance ...................................................................... 5 ESD Caution...................................................................................5 Typical Performance Characteristics ..............................................6 Applications Information .............................................................. 15 Input Protection ......................................................................... 15 Phase Reversal ............................................................................ 15 Micropower Instrumentation Amplifier ................................. 15 Hall Sensor Signal Conditioning .............................................. 16 Simplified Schematic ...................................................................... 17 Outline Dimensions ....................................................................... 18 Ordering Guide .......................................................................... 18
REVISION HISTORY
7/09--Revision 0: Initial Version
Rev. 0 | Page 2 of 20
AD8622 SPECIFICATIONS
ELECTRICAL CHARACTERISTICS--15 V OPERATION
VS = 15 V, VCM = 0 V, TA = +25C, unless otherwise specified. Table 2.
Parameter INPUT CHARACTERISTICS Offset Voltage Offset Voltage Drift Input Bias Current Input Offset Current Input Voltage Range Common-Mode Rejection Ratio Open-Loop Gain Input Resistance, Differential Mode Input Resistance, Common Mode Input Capacitance, Differential Mode Input Capacitance, Common Mode OUTPUT CHARACTERISTICS Output Voltage High Symbol VOS VOS/T IB IOS -40C TA +125C CMRR AVO RINDM RINCM CINDM CINCM VOH RL = 100 k to ground -40C TA +125C RL = 10 k to ground -40C TA +125C RL = 100 k to ground -40C TA +125C RL = 10 k to ground -40C TA +125C f = 1 kHz, AV = 1 VS = 2.0 V to 18.0 V -40C TA +125C IO = 0 mA -40C TA +125C RL = 10 k, AV = 1 CL = 35 pF, AV = 1 CL = 35 pF, AV = 1 f = 0.1 Hz to 10 Hz f = 1 kHz f = 1 kHz f = 1 kHz 125 120 14.94 14.84 14.86 14.75 VCM = -13.8 V to +13.8 V -40C TA +125C RL = 10 k, VO = -13.5 V to +13.5 V -40C TA +125C -13.8 125 112 125 120 135 137 1 1 5.5 3 14.97 14.89 -14.97 -14.89 40 1.5 145 215 250 350 -14.94 -14.92 -14.90 -14.80 -40C TA +125C -40C TA +125C -40C TA +125C 35 Conditions Min Typ 10 0.5 45 Max 125 230 1.2 200 500 200 500 +13.8 Unit V V V/C pA pA pA pA V dB dB dB dB G T pF pF V V V V V V V V mA dB dB A A V/s kHz Degrees V p-p nV/Hz pA/Hz pA/Hz
Output Voltage Low
VOL
Short-Circuit Current Closed-Loop Output Impedance POWER SUPPLY Power Supply Rejection Ratio Supply Current/Amplifier DYNAMIC PERFORMANCE Slew Rate Gain Bandwidth Product Phase Margin NOISE PERFORMANCE Voltage Noise Voltage Noise Density Uncorrelated Current Noise Density Correlated Current Noise Density
ISC ZOUT PSRR ISY
SR GBP M en p-p en in in
0.48 600 72 0.2 11 0.15 0.06
Rev. 0 | Page 3 of 20
AD8622
ELECTRICAL CHARACTERISTICS--2.5 V OPERATION
VS = 2.5 V, VCM = 0 V, TA = +25C, unless otherwise specified. Table 3.
Parameter INPUT CHARACTERISTICS Offset Voltage Offset Voltage Drift Input Bias Current Input Offset Current Input Voltage Range Common-Mode Rejection Ratio Open-Loop Gain Input Resistance, Differential Mode Input Resistance, Common Mode Input Capacitance, Differential Mode Input Capacitance, Common Mode OUTPUT CHARACTERISTICS Output Voltage High Symbol VOS VOS/T IB IOS -40C TA +125C -40C TA +125C VCM = -1.3 V to +1.3 V -40C TA +125C RL = 10 k, VO = -2.0 V to +2.0 V -40C TA +125C -1.3 110 107 118 109 -40C TA +125C -40C TA +125C -40C TA +125C 25 Conditions Min Typ 10 0.5 30 Max 125 230 1.2 200 400 200 300 +1.3 Unit V V V/C pA pA pA pA V dB dB dB dB G T pF pF V V V V V V V V mA dB dB A A V/s kHz Degrees V p-p nV/Hz pA/Hz pA/Hz
CMRR AVO RINDM RINDM CINDM CINCM VOH
120 135 1 1 5.5 3
Output Voltage Low
VOL
RL = 100 k to ground -40C TA +125C RL = 10 k to ground -40C TA +125C RL = 100 k to ground -40C TA +125C RL = 10 k to ground -40C TA +125C f = 1 kHz, AV = 1 VS = 2.0 V to 18.0 V -40C TA +125C IO = 0 mA -40C TA +125C RL = 10 k, AV = 1 CL = 35 pF, AV = 1 CL = 35 pF, AV = 1 f = 0.1 Hz to 10 Hz f = 1 kHz f = 1 kHz f = 1 kHz
2.45 2.41 2.40 2.36
2.49 2.45 -2.49 -2.45 30 2 -2.45 -2.41 -2.40 -2.36
Short-Circuit Current Closed-Loop Output Impedance POWER SUPPLY Power Supply Rejection Ratio Supply Current/Amplifier DYNAMIC PERFORMANCE Slew Rate Gain Bandwidth Product Phase Margin NOISE PERFORMANCE Voltage Noise Voltage Noise Density Uncorrelated Current Noise Density Correlated Current Noise Density
ISC ZOUT PSRR ISY
125 120
145 175 225 310
SR GBP M en p-p en in in
0.28 580 72 0.2 12 0.15 0.07
Rev. 0 | Page 4 of 20
AD8622 ABSOLUTE MAXIMUM RATINGS
Table 4.
Parameter Supply Voltage Input Voltage Input Current1 Differential Input Voltage2 Output Short-Circuit Duration to GND Storage Temperature Range Operating Temperature Range Junction Temperature Range Lead Temperature (Soldering, 60 sec)
1
Rating 18 V V supply 10 mA 10 V Indefinite -65C to +150C -40C to +125C -65C to +150C 300C
THERMAL RESISTANCE
JA is specified for the worst-case conditions, that is, a device soldered in a circuit board for surface-mount packages. This was measured using a standard 4-layer board. Table 5. Thermal Resistance
Package Type 8-Lead SOIC_N (R-8) 8-Lead MSOP (RM-8) JA 158 185 JC 43 53 Unit C/W C/W
The input pins have clamp diodes to the power supply pins. The input current should be limited to 10 mA or less whenever input signals exceed the power supply rail by 0.5 V. 2 Differential input voltage is limited to 10 V or the supply voltage, whichever is less.
ESD CAUTION
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. 0 | Page 5 of 20
AD8622 TYPICAL PERFORMANCE CHARACTERISTICS
TA = 25C, unless otherwise noted.
60 VSY = 15V VCM = 0V 50
50 60 VSY = 2.5V VCM = 0V
NUMBER OF AMPLIFIERS
07527-063
NUMBER OF AMPLIFIERS
40
40
30
30
20
20
10
10
-60
-40
-20
20 VOS (V)
0
40
60
80
100
-60
-40
-20
0 20 VOS (V)
40
60
80
100
Figure 3. Input Offset Voltage Distribution
Figure 6. Input Offset Voltage Distribution
60 VSY = 15V -40C TA +125C 50
60 VSY = 2.5V -40C TA +125C 50
NUMBER OF AMPLIFIERS
NUMBER OF AMPLIFIERS
40
40
30
30
20
20
10
10
07527-064
0
0.2
0.4
0.6 0.8 TCVOS (V/C)
1.0
1.2
0
0.2
0.4
0.6 0.8 TCVOS (V/C)
1.0
1.2
Figure 4. Input Offset Voltage Drift Distribution
Figure 7. Input Offset Voltage Drift Distribution
50 40 30 20 -40C VSY = 15V
50 40 30 20 VSY = 2.5V -40C
VOS (V)
VOS (V)
10 0 -10 -20 -30 -40
07527-004
10 0 -10 -20 -30 -40 +25C
+25C +85C +125C
+85C +125C
0
5
10
15 VCM (V)
20
25
30
-1.5
-0.5 VCM (V)
0.5
1.5
2.5
Figure 5. Input Offset Voltage vs. Common-Mode Voltage
Rev. 0 | Page 6 of 20
Figure 8. Input Offset Voltage vs. Common-Mode Voltage
07527-007
-50
-50 -2.5
07527-066
0
0
07527-065
0 -100 -80
0 -100 -80
AD8622
40 VSY = 15V 30 20 10 IB (pA) 0 -10 -20 -30
07527-008
40
IB+
20
VSY = 2.5V
0
IB+
IB (pA)
IB-
-20 IB-
-40
-60
-25
0
25
50
75
100
125
-25
0
25
50
75
100
125
TEMPERATURE (C)
TEMPERATURE (C)
Figure 9. Input Bias Current vs. Temperature
Figure 12. Input Bias Current vs. Temperature
60 VSY = 15V 40
50 VSY = 2.5V 25 0
20
-25
IB (pA)
0
IB (pA)
-50 -75 -100
-20
-40
-125
07527-009
07527-012
07527-013
-60
0
5
10
15 VCM (V)
20
25
30
-150
0
1
2 VCM (V)
3
4
5
Figure 10. Input Bias Current vs. Common-Mode Voltage
Figure 13. Input Bias Current vs. Common-Mode Voltage
100k
100k
OUTPUT VOLTAGE TO SUPPLY RAIL (mV)
10k
OUTPUT VOLTAGE TO SUPPLY RAIL (mV)
VSY = 15V
VSY = 2.5V 10k
1k VCC - VOH VOL - VEE 10
1k VCC - VOH 100
100
VOL - VEE
10
0.01
0.1 1 LOAD CURRENT (mA)
10
100
07527-010
1 0.001
1 0.001
0.01
0.1 1 LOAD CURRENT (mA)
10
100
Figure 11. Output Voltage to Supply Rail vs. Load Current
Figure 14. Output Voltage to Supply Rail vs. Load Current
Rev. 0 | Page 7 of 20
07527-011
-40 -50
-80 -50
AD8622
0.16
0.06
OUTPUT VOLTAGE TO SUPPLY RAIL (V)
0.14 0.12 0.10 0.08 0.06 VOL - VEE 0.04 0.02 VCC - VOH
OUTPUT VOLTAGE TO SUPPLY RAIL (V)
VSY = 15V RL = 10k
VSY = 2.5V RL = 10k 0.05 VCC - VOH 0.04
0.03
0.02 VOL - VEE 0.01
07527-014
-25
0
25 50 TEMPERATURE (C)
75
100
125
-25
0
25 50 TEMPERATURE (C)
75
100
125
Figure 15. Output Voltage to Supply Rail vs. Temperature
Figure 18. Output Voltage to Supply Rail vs. Temperature
100 80 60
GAIN (dB)
PHASE
VSY = 15V RL = 10k
100 80 60
100 80 60
PHASE (Degrees)
VSY = 2.5V RL = 10k PHASE
100 80 60 40
20 0 -20 -40 1k
GAIN
GAIN (dB)
40
40 20 0 -20 -40 10M
40 20 0 -20 -40 1k GAIN
20 0 -20 -40 10M
07527-015
10k
100k FREQUENCY (Hz)
1M
10k
100k FREQUENCY (Hz)
1M
Figure 16. Open-Loop Gain and Phase vs. Frequency
Figure 19. Open-Loop Gain and Phase vs. Frequency
60 50 40 30 AV = 100 VSY = 15V RL = 10k
60 50 40 30 AV = 10 AV = 100 VSY = 2.5V RL = 10k
GAIN (dB)
10 0 -10 -20 -30
GAIN (dB)
20
20 10 0 -10 -20 -30
AV = 10
AV = 1
AV = 1
07527-016
1k
10k 100k FREQUENCY (Hz)
1M
10M
1k
10k 100k FREQUENCY (Hz)
1M
10M
Figure 17. Closed-Loop Gain vs. Frequency
Figure 20. Closed-Loop Gain vs. Frequency
Rev. 0 | Page 8 of 20
07527-019
-40 100
-40 100
07527-018
PHASE (Degrees)
07527-017
0 -50
0 -50
AD8622
10k VSY = 15V 1k 1k AV = 10
ZOUT ()
10k VSY = 2.5V AV = 100 AV = 10 AV = 1 100 AV = 1
AV = 100
ZOUT ()
100
10
10
1
1
07527-020
1k
10k FREQUENCY (Hz)
100k
1M
1k
10k FREQUENCY (Hz)
100k
1M
Figure 21. Output Impedance vs. Frequency
Figure 24. Output Impedance vs. Frequency
120
VSY = 15V
120
VSY = 2.5V
100
100
80
CMRR (dB) CMRR (dB)
80
60
60
40
40
20
20
07527-021
100
1k 10k FREQUENCY (Hz)
100k
1M
100
1k 10k FREQUENCY (Hz)
100k
1M
Figure 22. CMRR vs. Frequency
Figure 25. CMRR vs. Frequency
120
VSY = 15V
120
VSY = 2.5V
100 PSRR+ 80
PSRR (dB) PSRR (dB)
100 PSRR+ 80
60 PSRR- 40
60 PSRR-
40
20
20
07527-022
100
1k 10k FREQUENCY (Hz)
100k
1M
100
1k 10k FREQUENCY (Hz)
100k
1M
Figure 23. PSRR vs. Frequency
Figure 26. PSRR vs. Frequency
Rev. 0 | Page 9 of 20
07527-025
0 10
0 10
07527-024
0 10
0 10
07527-023
0.1 100
0.1 100
AD8622
50 45 40 35 VSY = 15V AV = 1 RL = 10k
50 45 40 35
OVERSHOOT (%)
VSY = 2.5V AV = 1 RL = 10k
OVERSHOOT (%)
OS- 30 25 20 15 10 5 OS+
30 25 20 15 10 5
OS- OS+
0.1
1 CAPACITANCE (nF)
10
100
0.1
1 CAPACITANCE (nF)
10
100
Figure 27. Small-Signal Overshoot vs. Load Capacitance
Figure 30. Small-Signal Overshoot vs. Load Capacitance
VSY = 15V AV = 1 RL = 10k CL = 100pF
VSY = 2.5V AV = 1 RL = 10k CL = 100pF
VOLTAGE (500mV/DIV)
VOLTAGE (5V/DIV)
07527-027
TIME (40s/DIV)
TIME (40s/DIV)
Figure 28. Large-Signal Transient Response
Figure 31. Large-Signal Transient Response
VSY = 15V AV = 1 RL = 10k CL = 100pF
VOLTAGE (50mV/DIV) VOLTAGE (50mV/DIV)
VSY = 2.5V AV = 1 RL = 10k CL = 100pF
07527-028
TIME (10s/DIV)
TIME (10s/DIV)
Figure 29. Small-Signal Transient Response
Figure 32. Small-Signal Transient Response
Rev. 0 | Page 10 of 20
07527-031
07527-030
07527-029
07527-026
0 0.01
0 0.01
AD8622
0.4 0.2 INPUT 0
INPUT VOLTAGE (V)
0.4 VSY = 15V AV = -100 RL = 10k
OUTPUT VOLTAGE (V)
0.2 INPUT 0
VSY = 2.5V AV = -100 RL = 10k
OUTPUT 0 -10 -20
OUTPUT
0 -1 -2
07527-032
-3 TIME (20s/DIV)
TIME (20s/DIV)
Figure 33. Negative Overload Recovery
Figure 36. Negative Overload Recovery
0.2 0 -0.2 INPUT
0.2 0 -0.2 INPUT VOLTAGE (V) INPUT
OUTPUT VOLTAGE (V)
20 10 OUTPUT 0 VSY = 15V AV = -100 RL = 10k TIME (20s/DIV) -10
3 2 OUTPUT VSY = 2.5V AV = -100 RL = 10k TIME (20s/DIV) 1 0 -1
07527-033
-20
Figure 34. Positive Overload Recovery
Figure 37. Positive Overload Recovery
12 VSY = 15V AV = -1 10
12 VSY = 15V AV = +1 10
OUTPUT STEP (V)
OUTPUT STEP (V)
8 0.1% 6 0.01%
8 0.1% 6 0.01%
4
4
2
2
07527-034
0
5
10
15 20 25 SETTLING TIME (s)
30
35
0
5
10
15 20 25 SETTLING TIME (s)
30
35
Figure 35. Output Step vs. Settling Time
Figure 38. Output Step vs. Settling Time
Rev. 0 | Page 11 of 20
07527-037
0
0
07527-036
OUTPUT VOLTAGE (V)
INPUT VOLTAGE (V)
07527-035
OUTPUT VOLTAGE (V)
INPUT VOLTAGE (V)
AD8622
100 VSY = 15V
100 VSY = 2.5V
VOLTAGE NOISE DENSITY (nV/ Hz)
VOLTAGE NOISE DENSITY (nV Hz)
10
10
07527-039
1
10 FREQUENCY (Hz)
100
1k
1
10 FREQUENCY (Hz)
100
1k
Figure 39. Voltage Noise Density vs. Frequency
Figure 42. Voltage Noise Density vs. Frequency
1
RS1
1
VSY = 15V
RS1
VSY = 2.5V
RS2 UNCORRELATED RS1 = 0 0.1 CORRELATED RS1 = RS2
CURRENT NOISE DENSITY (pA/ Hz)
CURRENT NOISE DENSITY (pA/ Hz)
RS2 UNCORRELATED RS1 = 0 0.1 CORRELATED RS1 = RS2
07527-056
1
10 FREQUENCY (Hz)
100
1k
1
10 FREQUENCY (Hz)
100
1k
Figure 40. Current Noise Density vs. Frequency
Figure 43. Current Noise Density vs. Frequency
VSY = 15V
INPUT NOISE VOLTAGE (50nV/DIV)
VSY = 2.5V
INPUT NOISE VOLTAGE (50nV/DIV)
07527-040
TIME (1s/DIV)
TIME (1s/DIV)
Figure 41. 0.1 Hz to 10 Hz Noise
Figure 44. 0.1 Hz to 10 Hz Noise
Rev. 0 | Page 12 of 20
07527-043
07527-057
0.01
0.01
07527-042
1
1
AD8622
0.35 0.30 +125C 0.25 +85C 0.20 0.15 -40C 0.10 0.05 0
07527-044
0.35
0.30
0.25
ISY (mA)
ISY (mA)
+25C
VSY = 15V 0.20 VSY = 2.5V 0.15
0.10
0
2
4
6
8 10 VSY (V)
12
14
16
18
-25
0
25 50 75 TEMPERATURE (C)
100
125
Figure 45. Supply Current vs. Supply Voltage
Figure 48. Supply Current vs. Temperature
1 VSY = 15V f = 1kHz RL = 10k 0.1
1 VSY = 2.5V f = 1kHz RL = 10k 0.1
THD + N (%)
THD + N (%)
0.01
0.01
0.001
0.001
07527-046
0.01
0.1 AMPLITUDE (V rms)
1
10
0.01
0.1 AMPLITUDE (V rms)
1
10
Figure 46. THD + Noise vs. Amplitude
Figure 49. THD + Noise vs. Amplitude
0.1
VSY = 15V RL = 10k VIN = 300mV rms
0.1 VSY = 2.5V RL = 10k VIN = 300mV rms
0.01
0.01
THD + N (%)
0.001
THD + N (%)
0.001
07527-050
100
1k FREQUENCY (Hz)
10k
100k
100
1k FREQUENCY (Hz)
10k
100k
Figure 47. THD + Noise vs. Frequency
Figure 50. THD + Noise vs. Frequency
Rev. 0 | Page 13 of 20
07527-051
0.0001 10
0.0001 10
07527-049
0.0001 0.001
0.0001 0.001
07527-045
-0.05
0.05 -50
AD8622
0 100k -20 CHANNEL SEPARATION (dB) -40 -60 -80 -100 -120 -140 10 RL 1k
VSY = 2.5V TO 15V RL = 10k 100 1k FREQUENCY (Hz) 10k 100k
07527-048
Figure 51. Channel Separation vs. Frequency
Rev. 0 | Page 14 of 20
AD8622 APPLICATIONS INFORMATION
INPUT PROTECTION
The maximum differential input voltage that can be applied to the AD8622 is determined by the internal diodes connected across its inputs and series resistors at each input. These internal diodes and series resistors limit the maximum differential input voltage to 10 V and are needed to prevent base-emitter junction breakdown from occurring in the input stage of the AD8622 when very large differential voltages are applied. In addition, the internal resistors limit the currents that flow through the diodes. However, in applications where large differential voltages can be inadvertently applied to the device, large currents may still flow through these diodes. In such a case, external resistors must be placed at both inputs of the op amp to limit the input currents to 10 mA (see Figure 52).
VOUT
VOLTAGE (5V/DIV)
VIN
VSY = 15V
TIME (200s/DIV)
Figure 53. No Phase Reversal
MICROPOWER INSTRUMENTATION AMPLIFIER
R1 2 500
AD8622
R2 3 500
1/2
1
07527-055
The AD8622 is a dual, high precision, rail-to-rail output op amp operating at just 215 A quiescent current per amplifier. Its ultralow offset, offset drift, and voltage noise, combined with its very low bias current and high common-mode rejection ratio (CMRR), are ideally suited for high accuracy and micropower instrumentation amplifier. Figure 54 shows the classic 2-op-amp instrumentation amplifier with four resistors using the AD8622. The key to high CMRR for this instrumentation amplifier are resistors that are well matched from both the resistive ratio and the relative drift. For true difference amplification, matching of the resistor ratio is very important, where R3/R4 = R1/R2. Assuming perfectly matched resistors, the gain of the circuit is 1 + R2/R1, which is approximately 100. Tighter matching of two op amps in one package, like the AD8622, offers a significant boost in performance over the classical 3-op-amp configuration. Overall, the circuit only requires about 430 A of supply current.
R3 10.1k +15V R2 1M R1 10.1k +15V
Figure 52. Input Protection
PHASE REVERSAL
An undesired phenomenon, phase reversal (also known as phase inversion) occurs in many op amps when one or both of the inputs are driven beyond the specified input voltage range (IVR), in effect reversing the polarity of the output. In some cases, phase reversal can induce lockups and even cause equipment damage as well as self destruction. The AD8622 amplifiers have been carefully designed to prevent output phase reversal when both inputs are maintained within the specified input voltage range. In addition, even if one or both inputs exceed the input voltage range but remain within the supply rails, the output still does not phase reverse. Figure 53 shows the input/output waveforms of the AD8622 configured as a unity-gain buffer with a supply voltage of 15 V.
R4 1M
-
AD8622
V1
1/2
-
+
-15V V2
AD8622
+
1/2
VO
NOTES -15V 1. VO = 100(V2 - V1) 2. TYPICAL: 0.01mV < |V2 - V1| < 149.7mV 3. TYPICAL: -14.97V < VO < +14.97V 4. USE MATCHED RESISTORS.
Figure 54. Micropower Instrumentation Amplifier
Rev. 0 | Page 15 of 20
07527-054
07527-053
AD8622
HALL SENSOR SIGNAL CONDITIONING
The AD8622 is also highly suitable for high accuracy, low power signal conditioning circuits. One such use is in Hall sensor signal conditioning (see Figure 55). The magnetic sensitivity of a Hall element is proportional to the bias voltage applied across it. With 1 V bias voltage, the Hall element consumes about 2.5 mA of supply current and has a sensitivity of 5.5 mV/mT typical. To reduce power consumption, bias voltage must be reduced, but at the risk of lower sensitivity. The only way to achieve higher sensitivity is by introducing a gain using a precision micropower amplifier. The AD8622, with all its features, is well suited to amplify the sensitivity of the Hall element.
VSY C1 1F TO 10F ADR121 -2.5V 4.12k C2 0.1F C3 + 0.1F TO 10F VSY VSY
The ADR121 is a precision micropower 2.5 V voltage reference. A precision voltage reference is required to hold a constant current so that the Hall voltage only depends on the intensity of the magnetic field. Using the 4.12k:98.8k resistive divider, the bias voltage of the Hall element is reduced to 100 mV, leading to only 250 A of power consumption. The 3-op-amp in-amp configuration of the AD8622 then increases the sensitivity to 55 mV/mT. Using the AD8622 to amplify the sensor signal can reduce power while also achieving higher sensitivity. The total current consumed is just 1.2 mA, resulting in 21x improvement in sensitivity/power.
+
HALL ELEMENT
AD8622
-
9.9k 9.9k
1/2
9.9k VSY
-
+
98.8k
AD8622
- -
1/2
400 x4
200 9.9k VSY 9.9k
AD8622
+
VOUT = 2.5V +
1/2
55mV x MAGNETIC FIELD (mT) mT
AD8622
+
NOTES 1. USE MATCHED RESISTORS FOR IN-AMP. 2. FOR INFORMATION ON C1, C2, AND C3, REFER TO ADR121 DATA SHEET.
1/2
9.9k
Figure 55. Hall Sensor Signal Conditioning
Rev. 0 | Page 16 of 20
07527-052
AD8622 SIMPLIFIED SCHEMATIC
V+ R3 R2 R1 C1 Q3 Q4 +IN x 500 D1 D2 Q1 Q2 VB1 INPUT BIAS CANCELLATION CIRCUITRY VB2 Q5 Q8 OUT x Q6 Q10 Q11
-IN x
500
Q7 D3 V- D4
Q9
Q12
07527-062
Figure 56. Simplified Schematic
Rev. 0 | Page 17 of 20
AD8622 OUTLINE DIMENSIONS
3.20 3.00 2.80
3.20 3.00 2.80 PIN 1
8
5
1
5.15 4.90 4.65
4
0.65 BSC 0.95 0.85 0.75 0.15 0.00 0.38 0.22 SEATING PLANE 1.10 MAX 8 0 0.80 0.60 0.40
0.23 0.08
COPLANARITY 0.10
COMPLIANT TO JEDEC STANDARDS MO-187-AA
Figure 57. 8-Lead Mini Small Outline Package [MSOP] (RM-8) Dimensions shown in millimeters
5.00 (0.1968) 4.80 (0.1890)
4.00 (0.1574) 3.80 (0.1497)
8 1
5 4
6.20 (0.2441) 5.80 (0.2284)
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)
0.50 (0.0196) 0.25 (0.0099) 8 0 0.25 (0.0098) 0.17 (0.0067) 1.27 (0.0500) 0.40 (0.0157)
45
0.51 (0.0201) 0.31 (0.0122)
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 58. 8-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-8) Dimensions shown in millimeters and (inches)
ORDERING GUIDE
Model AD8622ARMZ 1 AD8622ARMZ-REEL1 AD8622ARMZ-R71 AD8622ARZ1 AD8622ARZ-REEL1 AD8622ARZ-REEL71
1
Temperature Range -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C
Package Description 8-Lead MSOP 8-Lead MSOP 8-Lead MSOP 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N
Package Option RM-8 RM-8 RM-8 R-8 R-8 R-8
012407-A
Branding A1P A1P A1P
Z = RoHS Compliant Part.
Rev. 0 | Page 18 of 20
AD8622 NOTES
Rev. 0 | Page 19 of 20
AD8622 NOTES
(c)2009 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D07527-0-7/09(0)
Rev. 0 | Page 20 of 20

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