High Performance, Low Power, Rail-to-Rail Precision ...

1 High performance , Low Power, Rail-to-Rail Precision Instrumentation Amplifier data Sheet AD8422 Rev. B Document Feedback Information furnished by Analog Devices is believed to be accurate and reliable. Howeve r, n o 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, Box 9106, Norwood, MA 02062-9106, Tel: 2013 2021 Analog Devices, Inc. All rights reserved. Technical Support FEATURES Low power: 330 A maximum quiescent current Rail-to-Rail output Low noise and distortion 8 nV/ Hz maximum input voltage noise at 1 kHz V p-p RTI noise (G = 100) ppm nonlinearity with 2 k load (G = 1) Excellent ac specifications 80 dB minimum CMRR at 10 kHz (G = 1) MHz bandwidth (G = 1) High Precision dc performance (AD8422 BRZ) 150 dB minimum CMRR (G = 1000) maximum gain error (G = 1000) V/ C maximum input offset drift nA maximum input bias current Wide supply range V to 36 V single supply V to 18 V dual supply Input overvoltage protection: 40 V from opposite supply Gain range.

2 1 to 1000 Available in 8-lead LFCSP, 8-lead MSOP, and 8-lead SOIC_N APPLICATIONS Medical instrumentation Industrial process controls Strain gages Transducer interfaces Precision data acquisition systems Channel-isolated systems Portable instrumentation GENERAL DESCRIPTION The AD8422 is a high Precision , low power, low noise, rail -to -rail instrumentation amplifier that delivers the best performance per unit microampere in the industry. The AD8422 processes signals with ultralow distortion performance that is load independent over its full output range. The AD8422 is the third generation development of the industry-standard AD620. The AD8422 employs new process technologies and design techniques to achieve higher dynamic range and lower errors than its predecessors, while consuming less than one-third of the power. The AD8422 uses the high performance pinout introduced by the AD8221. Ve r y low bias current makes the AD8422 error free with high source impedance, allowing multiple sensors to be multiplexed to the inputs.

3 Low voltage noise and low current noise make the AD8422 an ideal choice for measuring a Wheatstone bridge. TYPICAL APPLICATION DIAGRAM +5V+5V+5 VREF+24V+ 11 OPTIONAL ZERO ADJUST INVOUT_FS = 15mVV = TO = 301 G = Figure 1. Bridge Amplifier with Output Zero Adjust The wide input range and Rail-to-Rail output of the AD8422 bring all of the benefits of a high performance in-amp to single-supply applications. Whether using high or low supply voltages, the power savings make the AD8422 an excellent choice for high channel count or power sensitive applications. The AD8422 uses robust input protection that ensures reliability without sacrificing noise performance . The AD8422 has high ESD immunity, and the inputs are protected from continuous voltages up to 40 V from the opposite supply rail. A single resistor sets the gain from 1 to 1000. The reference pin can be used to apply a precise offset to the output voltage. The AD8422 is specified from 40 C to +85 C for the 8-lead MSOP and the 8-lead SOIC_N and from 40 C to +125 C for the 8-lead LFCSP.

4 140 130 120 110 100 90 80 70 60 50 40 30 20101001k5kAMPLITUDE (dBc)FREQUENCY (Hz)RL= 2k VOUT= 10VG = 1000G = 100G = 10G = 111197-102 Figure 2. Total Harmonic Distortion vs. Frequency AD8422 data Sheet Rev. B | Page 2 of 27 TABLE OF CONTENTS Features .. 1 Applications .. 1 General Description .. 1 Typical Application Diagram .. 1 Revision History .. 2 Specifications .. 3 3 MSOP .. 5 LFCSP .. 7 Absolute Maximum Ratings .. 10 Thermal Resistance .. 10 Electrostatic Discharge (ESD) Ratings .. 10 ESD Caution .. 10 Pin Configurations and Function Descriptions .. 11 Typical performance Characteristics .. 12 Theory of Operation .. 21 Architecture .. 21 Gain Selection .. 21 Reference Terminal .. 22 Input Voltage Range .. 22 Layout .. 22 Input Bias Current Return Path .. 23 Input Voltages Beyond the Supply Rails .. 23 RF Interference (RFI) .. 24 Applications Information .. 25 Precision Bridge Conditioning .. 25 Process Control Analog Input .. 25 Outline Dimensions .. 26 Ordering Guide.

5 27 REVISION HISTORY 4/ 2021 R e v. A to Rev. B Added 8-Lead LFCSP .. Universal Changes to Features Section and General Description Section . 1 Deleted Connection Diagram, Figure 1; Renumbered Sequentially .. 1 Added Typical Application Diagram, Figure 1; Renumbered Sequentially .. 1 Changes to Table 1 .. 3 Changes to Table 2 .. 5 Added LFCSP Section and Table 3; Renumbered Sequentially .. 7 Changes to Thermal Resistance Section and Ta b l e 5 .. 10 Added Electrostatic Discharge (ESD) Ratings Section, ESD Ratings for AD8422 Section, and Table 6 .. 10 Added Figure 4; Renumbered Sequentially .. 11 Changes to Table 7 .. 11 Changes to Figure 32 .. 16 Updated Outline Dimensions .. 26 Changes to Ordering Guide .. 27 1/ 2015 Rev. 0 to Rev. A Changes to Features Section .. 1 Changes to SOIC Package Section and Table 1 .. 4 Changes to MSOP Package Section and Table 2 .. 5 Changes to Supply Voltage Parameter and ESD Parameter, Ta b l e 3 .. 8 Deleted Figure 12 and Figure 15, Renumbered Sequentially.

6 11 Changes to Figure 10 to Figure 15 .. 11 Changes to Figure 16, Figure 18, and Figure 19 .. 12 Changes to Figure 23 and Figure 13 Changes to Figure 31, Figure 32, and Figure 33 .. 14 Changes to Figure 64 .. 23 5/ 2013 Revision 0: Initial Version data Sheet AD8422 Rev. B | Page 3 of 27 SPECIFICATIONS SOIC_N VS = 15 V, VREF = 0 V, V+IN = 0 V, V IN = 0 V, TA = 25 C, G = 1, and RL = 2 k , unless otherwise noted. Table 1. Parameter Test Conditions/ Comments AD8422 ARZ AD8422 BRZ Unit Min Typ Max Min Typ Max COMMON-MODE REJECTION RATIO CMRR DC to 60 Hz with 1 k VCM = 10 V to +10 V 86 94 dB 106 114 dB 126 134 dB 146 150 dB Source Imbalance G = 1 G = 10 G = 100 G = 1000 Over Temperature, G = 1 T = 40 C to +85 C 83 89 dB CMRR at 10 kHz VCM = 10 V to +10 V G = 1 80 80 dB G = 10 90 95 dB G = 100 100 100 dB G = 1000 100 100 dB NOISE1 Voltage Noise, 1 kHz Input Voltage Noise, eNI VIN+, VIN , VREF = 0 V 8 8 nV/ Hz Output Voltage Noise, eNO 80 80 nV/ Hz Peak to Peak, RTI f = Hz to 10 Hz G = 1 2 2 V p-p G = 10 V p-p G = 100 to 1000 V p-p Current Noise f = 1 kHz 90 90 110 fA/ Hz f = Hz to 10 Hz 8 8 pA p-p VOLTAGE OFFSET2 Input Offset, VOSI VS = V to 15 V 60 25 V Over Temperature T = 40 C to +85 C 70 40 V Average Temperature Coefficient V/ C Output Offset.

7 VOSO VS = V to 15 V 300 150 V Over Temperature T = 40 C to +85 C 500 300 V Average Temperature Coefficient 5 2 V/ C Offset RTI vs. Supply (PSR) VS = V to 18 V G = 1 90 110 100 120 dB G = 10 110 130 120 140 dB G = 100 124 150 140 160 dB G = 1000 130 150 140 160 dB INPUT CURRENT Input Bias Current VS = V to 15 V 1 nA Over Temperature T = 40 C to +85 C 2 1 nA Average Temperature Coefficient 4 4 pA/ C Input Offset Current VS = V to 15 V nA Over Temperature T = 40 C to +85 C nA Average Temperature Coefficient 1 1 pA/ C AD8422 data Sheet Rev. B | Page 4 of 27 Parameter Test Conditions/ Comments AD8422 ARZ AD8422 BRZ Unit Min Typ Max Min Typ Max REFERENCE INPUT RIN 20 20 k IIN VIN+, VIN , VREF = 0 V 35 50 35 50 A Voltage Range VS +VS VS +VS V Gain to Output 1 1 V/V DYNAMIC RESPONSE Small Signal 3 dB Bandwidth G = 1 2200 2200 kHz G = 10 850 850 kHz G = 100 120 120 kHz G = 1000 12 12 kHz Settling Time 10 V step G = 1 13 13 s G = 10 13 13 s G = 100 12 12 s G = 1000 80 80 s Settling Time 10 V step G = 1 15 15 s G = 10 15 15 s G = 100 15 15 s G = 1000 160 160 s Slew Rate G = 1 to 100 V/ s GAIN3 G = 1 + ( k /RG)

8 Gain Range 1 1000 1 1000 V/V Gain Error VOUT 10 V G = 1 % G = 10 % G = 100 % G = 1000 % Gain Nonlinearity VOUT = 10 V to +10 V G = 1 RL = 2 k 5 5 ppm G = 10 2 5 2 5 ppm G = 100 4 10 4 10 ppm G = 1000 10 20 10 20 ppm Gain vs. Temperature G = 1 5 1 ppm/ C G > 1 80 80 ppm/ C INPUT Input Impedance Differential 200||2 200||2 G ||pF Common Mode 200||2 200||2 G ||pF Input Operating Voltage Range4, 5 VS = V to 18 V VS + +VS VS + +VS V Over Temperature T = 40 C to +85 C VS + +VS VS + +VS V OUTPUT Output Swing, RL = 10 k VS = 15 V VS + +VS VS + +VS V Over Temperature T = 40 C to +85 C VS + +VS VS + +VS V Output Swing, RL = 10 k VS = V VS + +VS VS + +VS V Over Temperature T = 40 C to +85 C VS + +VS VS + +VS V Output Swing, RL = 2 k VS = 15 V VS + +VS VS + +VS V Over Temperature6 T = 40 C to +85 C VS + +VS VS + +VS V Output Swing, RL = 2 k VS = V VS + +VS VS + +VS V Over Temperature T = 40 C to +85 C VS + +VS VS + +VS V data Sheet AD8422 Rev.

9 B | Page 5 of 27 Parameter Test Conditions/ Comments AD8422 ARZ AD8422 BRZ Unit Min Typ Max Min Typ Max Short-Circuit Current 20 20 mA POWER SUPPLY Operating Range Dual-supply operation 18 18 V Single-supply operation 36 36 V Quiescent Current 300 330 300 330 A Over Temperature T = 40 C to +85 C 400 400 A TEMPERATURE RANGE Specified performance 40 +85 40 +85 C Operating Range7 40 +125 40 +125 C 1 Total RTI noise = eNI2 + (eNO/G)2 2 Total RTI VOS = (VOSI) + (VOSO/G). 3 Gain does not include the effects of the external resistor, RG. 4 One input grounded. G = 1. 5 Only specified to guarantee linear output voltage. If linear bias current is required, use the following voltage range: VS + 2 V to +VS V. See Figure 19 and Figure 20. 6 Output current limited at cold temperatures. See Figure 34. 7 See Typical performance Characteristics for expected operation between 85 C and 125 C. MSOP VS = 15 V, VREF = 0 V, V+IN = 0 V, V IN = 0 V, TA = 25 C, G = 1, and RL = 2 k , unless otherwise noted.

10 Table 2. Parameter Test Conditions/ Comments AD8422 ARMZ AD8422 BRMZ Unit Min Typ Max Min Typ Max COMMON-MODE REJECTION RATIO CMRR DC to 60 Hz with 1 k Source Imbalance VCM = 10 V to +10 V G = 1 86 90 dB G = 10 106 110 dB G = 100 126 130 dB G = 1000 146 150 dB Over Temperature, G = 1 T = 40 C to +85 C 83 86 CMRR at 10 kHz VCM = 10 V to +10 V G = 1 80 80 dB G = 10 90 95 dB G = 100 100 100 dB G = 1000 100 100 dB NOISE1 Voltage Noise, 1 kHz Input Voltage Noise, eNI VIN+, VIN , VREF = 0 V 8 8 nV/ Hz Output Voltage Noise, eNO 80 80 nV/ Hz Peak to Peak, RTI f = Hz to 10 Hz G = 1 2 2 V p-p G = 10 V p-p G = 100 to 1000 V p-p Current Noise f = 1 kHz 90 90 110 fA/ Hz f = Hz to 10 Hz 8 8 pA p-p VOLTAGE OFFSET2 Input Offset, VOSI VS = V to 15 V 70 50 V Over Temperature T = 40 C to +85 C 110 75 V Average Temperature Coefficient V/ C Output Offset, VOSO VS = V to 15 V 300 150 V Over Temperature T = 40 C to +85 C 500 300 V Average Temperature 5 2 V/ C AD8422 data Sheet Rev.