AD8293G160BRJZ-R7

Low Cost, Zero-Drift In-Amp with Filter and Fixed Gain AD8293G80/AD8293G160 FEATURES Small package: 8-lead SOT-23 Reduced component count Incorporates gain resistors and filter resistors Low offset voltage: 20 μV maximum Low offset drift: 0.3 μV/°C maximum Low gain drift: 25 ppm/°C maximum High CMR: 140 dB typical Low noise: 0.7 μV p-p from 0.01 Hz to 10 Hz Single-supply operation: 1.8 V to 5.5 V Rail-to-rail output Available in 2 fixed-gain models FUNCTIONAL BLOCK DIAGRAM 7 5 6 +VS +IN R1 4kΩ 1 FILT R2 OUT 8 IN-AMP R3 5kΩ ADC OUT 4 –IN OUTPUT TO ADC WITH ANTIALIASING FILTER 07451-001 GND REF 2 3 AD8293Gxx Figure 1. +5V APPLICATIONS Current sensing Strain gauges Laser diode control loops Portable medical instruments Thermocouple amplifiers 0.1µF 7 5 C2 6 +VS LOAD 8 FILT R2 OUT +IN R1 4kΩ IN-AMP I RSHUNT 1 R3 5kΩ ADC OUT 4 ADC C3 +3.3V REF –IN GND REF 2 3 1.8V DC-DC Figure 2. Measuring Current Using the AD8293G80/AD8293G160 Table 1. AD8293Gxx Models and Gains Model AD8293G80 AD8293G160 Gain 80 160 GENERAL DESCRIPTION The AD8293G80/AD8293G160 are small, low cost, precision instrumentation amplifiers that have low noise and rail-to-rail outputs. They are available in two fixed-gain models: 80 and 160. They incorporate the gain setting resistors and filter resistors, reducing the number of ancillary components. For example, only two external capacitors are needed to implement a 2-pole filter. The AD8293G80/AD8293G160 also feature low offset voltage, offset drift, and gain drift coupled with high commonmode rejection. They are capable of operating on a supply of 1.8 V to 5.5 V. With a low offset voltage of 20 μV (AD8293G160B), an offset voltage drift of 0.3 μV/°C, and a voltage noise of only 0.7 μV p-p (0.01 Hz to 10 Hz), the AD8293G80/AD8293G160 are ideal for applications where error sources cannot be tolerated. Precision instrumentation, position and pressure sensors, medical instrumentation, and strain gauge amplifiers benefit from the low noise, low input bias current, and high commonmode rejection. The small footprint and low cost are ideal for high volume applications. The small package and low power consumption allow the maximum channel density and the minimum board size required for portable systems. Designed for ease of use, these instrumentation amplifiers, unlike more traditional ones, have a buffered reference, eliminating the need for an additional op amp to set the reference voltage to midsupply. The AD8293G80/AD8293G160 are specified over the industrial temperature range from −40°C to +85°C. The AD8293G80/ AD8293G160 are available in a halogen-free, Pb-free, 8-lead SOT-23. 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 ©2008 Analog Devices, Inc. All rights reserved. 07451-002 AD8293Gxx 0.1µF 10µF AD8293G80/AD8293G160 TABLE OF CONTENTS Features .............................................................................................. 1  Applications ....................................................................................... 1  Functional Block Diagram .............................................................. 1  General Description ......................................................................... 1  Revision History ............................................................................... 2  Specifications..................................................................................... 3  Electrical Characteristics ............................................................. 3  Absolute Maximum Ratings............................................................ 5  Thermal Resistance ...................................................................... 5  ESD Caution .................................................................................. 5  Pin Configuration and Function Descriptions ............................. 6  Typical Performance Characteristics ............................................. 7  Theory of Operation ...................................................................... 10  High PSR and CMR ................................................................... 10  1/f Noise Correction .................................................................. 10  Applications Information .............................................................. 11  Overview ..................................................................................... 11  Reference Connection ............................................................... 11  Output Filtering .......................................................................... 11  Clock Feedthrough..................................................................... 12  Power Supply Bypassing ............................................................ 12  Input Overvoltage Protection ................................................... 12  Outline Dimensions ....................................................................... 13  Ordering Guide .......................................................................... 13  REVISION HISTORY 8/08—Revision 0: Initial Version Rev. 0 | Page 2 of 16 AD8293G80/AD8293G160 SPECIFICATIONS ELECTRICAL CHARACTERISTICS VCC = 5.0 V, VCM = −0 V, VREF = 3.3 V, VIN = VINP − VINN, TA = 25°C, tested at ADC OUT, unless otherwise noted. Temperature specifications guaranteed by characterization. Table 2. A Grade Parameter COMMON-MODE REJECTION NOISE PERFORMANCE Voltage Noise Voltage Noise Density INPUT CHARACTERISTICS Input Offset Voltage vs. Temperature Input Bias Current Input Offset Current Input Operating Impedance Differential Common Mode Input Voltage Range DYNAMIC RESPONSE Small Signal Bandwidth 1 Slew Rate Settling Time 2 0.1% 0.01% Internal Clock Frequency GAIN Gain Error Gain Drift Nonlinearity OUTPUT CHARACTERISTICS Output Voltage High Output Voltage Low Short-Circuit Current REFERENCE CHARACTERISTICS VREF Range REF Pin Current POWER SUPPLY Operating Range Power Supply Rejection Supply Current TEMPERATURE RANGE Specified Range 1 2 Symbol CMR Conditions VCM = 0 V to 3.3 V, −40°C ≤ TA ≤ +85°C f = 0.01 Hz to 10 Hz f = 1 kHz Min 94 AD8293G80A Typ Max 140 Min 94 AD8293G160A Typ Max 140 Unit dB en p-p en VOS ΔVOS/ΔT IB IOS 0.7 35 9 0.02 0.4 50 0.3 2 4 0.7 35 9 0.02 0.4 50 0.3 2 4 μV p-p nV/√Hz μV μV/°C nA nA MΩ||pF GΩ||pF V Hz −40°C ≤ TA ≤ +85°C −40°C ≤ TA ≤ +85°C 50||1 10||10 0 BW SR ts Filter limited VCC − 1.7 500 Filter limited 1.9 2.4 60 80 0.3 5 0.003 VCC − 0.075 0.075 ±35 0.8 IREF 1.8 94 0.01 VCC − 0.8 1 5.5 120 1.0 1.3 1.5 +85 −40 0.8 0 50||1 10||10 VCC − 1.7 500 Filter limited 1.9 2.4 60 160 0.3 5 0.003 VCC − 0.075 0.075 ±35 VCC − 0.8 1 5.5 120 1.0 1.3 1.5 +85 500 Hz filter, VO = 2 V step ms ms kHz 1 25 0.03 % ppm/°C % FS V V mA V nA V dB mA mA °C VO = 0.075 V to 4.925 V −40°C ≤ TA ≤ +85°C VO = 0.075 V to 4.925 V VOH VOL ISC 1 25 0.03 0.01 1.8 94 PSR ISY VCC = 1.8 V to 5.5 V, VCM = 0 V IO = 0 mA, VIN = 0 V −40°C ≤ TA ≤ +85°C −40 Higher bandwidths result in higher noise. Settling time is determined by filter setting. Rev. 0 | Page 3 of 16 AD8293G80/AD8293G160 VCC = 2.7 V to 5.0 V, VCM = −0 V, VREF = VCC/2, VIN = VINP − VINN, TA = 25°C, tested at OUT with 10 kΩ load and ADC OUT, unless otherwise noted. Temperature specifications guaranteed by characterization. Table 3. B Grade (Tested and Guaranteed over a Wider Supply Range to More Stringent Specifications Than the A Grade) Parameter COMMON-MODE REJECTION Symbol CMR Conditions VCC = 5 V, VCM = 0 V to 3.3 V; −40°C ≤ TA ≤ +85°C VCC = 2.7 V, VCM = 0 V to 1 V; −40°C ≤ TA ≤ +85°C f = 0.01 Hz to 10 Hz f = 1 kHz Min 110 106 AD8293G80B Typ Max 140 140 Min 110 106 AD8293G160B Typ Max 140 140 Unit dB dB NOISE PERFORMANCE Voltage Noise Voltage Noise Density INPUT CHARACTERISTICS Input Offset Voltage vs. Temperature vs. Temperature Input Bias Current Input Offset Current Input Operating Impedance Differential Common Mode Input Voltage Range DYNAMIC RESPONSE Small Signal Bandwidth 1 Slew Rate Settling Time 2 0.1% 0.01% Internal Clock Frequency GAIN Gain Error Gain Drift Nonlinearity OUTPUT CHARACTERISTICS Output Voltage High Output Voltage Low Short-Circuit Current REFERENCE CHARACTERISTICS VREF Range REF Pin Current POWER SUPPLY Operating Range Power Supply Rejection Supply Current TEMPERATURE RANGE Specified Range 1 2 en p-p en VOS ΔVOS/ΔT ΔVOS/ΔT IB IOS 0.7 35 5 0.02 0.01 0.4 30 0.3 0.5 2 4 0.7 35 3 0.02 0.01 0.4 20 0.3 0.5 2 4 μV p-p nV/√Hz μV μV/°C μV/°C nA nA MΩ||pF GΩ||pF V Hz −40°C ≤ TA ≤ +85°C, VCC = 5 V −40°C ≤ TA ≤ +85°C, VCC = 2.7 V −40°C ≤ TA ≤ +85°C 50||1 10||10 0 BW SR ts 500 Hz filter, VO = 2 V step; measured at ADC OUT Filter limited; measured at ADC OUT 500 Filter limited 1.9 2.4 60 80 0.3 5 0.003 VCC − 0.075 0.075 VCC = 5 V VCC = 2.7 V 0.8 IREF 1.8 100 0.01 ±35 ±25 VCC − 0.8 1 5.5 120 1.0 1.3 1.5 +85 −40 0.8 VCC − 1.7 0 50||1 10||10 VCC − 1.7 500 Filter limited 1.9 2.4 60 160 0.3 5 0.003 VCC − 0.075 0.075 ±35 ±25 VCC − 0.8 1 5.5 120 1.0 1.3 1.5 +85 ms ms kHz 0.5 25 0.009 % ppm/°C % FS V V mA mA V nA V dB mA mA °C VO = 0.075 V to 4.925 V −40°C ≤ TA ≤ +85°C VO = 0.075 V to 4.925 V VOH VOL ISC 0.5 25 0.009 0.01 1.8 100 PSR ISY VCC = 1.8 V to 5.5 V, VCM = 0 V IO = 0 mA, VIN = 0 V −40°C ≤ TA ≤ +85°C −40 Higher bandwidths result in higher noise. Settling time is determined by filter setting. Rev. 0 | Page 4 of 16 AD8293G80/AD8293G160 ABSOLUTE MAXIMUM RATINGS Table 4. Parameter Supply Voltage Input Voltage Differential Input Voltage1 Output Short-Circuit Duration to GND Storage Temperature Range (RJ Package) Operating Temperature Range Junction Temperature Range (RJ Package) Lead Temperature (Soldering, 10 sec) 1 Rating 6V +VSUPPLY ±VSUPPLY Indefinite −65°C to +150°C −40°C to +85°C −65°C to +150°C 300°C 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. THERMAL RESISTANCE θJA is specified for the worst-case conditions, that is, a device soldered in a circuit board for surface-mount packages. Table 5. Package Type 8-Lead SOT-23 (RJ) 1 Differential input voltage is limited to ±5.0 V, the supply voltage, or whichever is less. θJA1 211.5 θJC 91.99 Unit °C/W θJA is specified for the nominal conditions, that is, θJA is specified for the device soldered on a circuit board. ESD CAUTION Rev. 0 | Page 5 of 16 AD8293G80/AD8293G160 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS –IN GND REF ADC OUT 1 AD8293Gxx 8 +IN +VS OUT FILT 07451-003 2 7 3 6 4 5 TOP VIEW (Not to Scale) Figure 3. Pin Configuration Table 6. Pin Function Descriptions Pin No. 1 2 3 4 5 6 7 8 Mnemonic −IN GND REF ADC OUT FILT OUT +VS +IN Description Inverting Input Terminal (True Differential Input) Ground Reference Voltage Terminal (Drive This Terminal to Level-Shift the Output) Output with Series 5 kΩ Resistor for Use with an Antialiasing Filter Place a capacitor across FILT and OUT to limit the amount of switching noise at the output (see Applications Information) Output Terminal Without Integrated Filter Positive Power Supply Terminal Noninverting Input Terminal (True Differential Input) Rev. 0 | Page 6 of 16 AD8293G80/AD8293G160 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, VCC = 5 V, and VREF = VCC/2; G = 80, C2 = 1300 pF, and C3 = 39 nF; G = 160, C2 = 680 pF, and C3 = 39 nF, unless otherwise specified. 60 VCC = 2.7V, 5V FILTER = 500Hz 60 G = 160 40 VCC = 2.7V, 5V FILTER = 10kHz 40 G = 160 20 G = 80 0 GAIN (dB) GAIN (dB) G = 80 20 0 –20 07451-004 100 1k FREQUENCY (Hz) 10k 100k 100 1k FREQUENCY (Hz) 10k 100k Figure 4. Gain vs. Frequency 180 160 140 120 CMR (dB) 180 160 140 120 Figure 7. Gain vs. Frequency VCC = 2.7V, 5V GAIN = 80, 160 FILTER = 500Hz VCC = 2.7V, 5V GAIN = 80, 160 FILTER = 10kHz 100 80 60 40 20 10 CMR (dB) 100 80 60 40 20 10 100 1k FREQUENCY (Hz) 10k 100k FREQUENCY (Hz) Figure 5. Common-Mode Rejection (CMR) vs. Frequency 4 (0.02V, 3.3V) INPUT COMMON-MODE VOLTAGE (V) 4 Figure 8. Common-Mode Rejection (CMR) vs. Frequency (4.98V, 3.3V) VCC = 5V, VREF = VCC/2 INPUT COMMON-MODE VOLTAGE (V) 3 (0.02V, 3V) (4.98V, 3V) 3 VCC = 5V, VREF = VCC/2 2 (0.02V, 1V) 1 VCC = 2.7V, VREF = VCC/2 (0.02V, 0V) –1 –1 0 1 2 3 4 2 (0.02V, 1V) 1 (2.68V, 1V) (2.68V, 1V) VCC = 2.7V, VREF = VCC/2 (2.68V, 0V) (0.02V, 0V) (4.98V, 0V) 0 0 (2.68V, 0V) (4.98V, 0V) 5 6 07451-019 0 1 2 3 4 5 6 07451-018 –1 –1 OUTPUT VOLTAGE (V) OUTPUT VOLTAGE (V) Figure 6. Input Common-Mode Voltage Range vs. Output Voltage, G = 80 Figure 9. Input Common-Mode Voltage Range vs. Output Voltage, G = 160 Rev. 0 | Page 7 of 16 07451-008 100 1k 10k 100k 07451-005 07451-007 –40 10 –20 10 AD8293G80/AD8293G160 10 POWER SUPPLY ON 5 0 –5 –10 –15 –20 –25 –0.2 GAIN = 160 10 POWER SUPPLY ON INPUT OFFSET VOLTAGE (5mV/DIV) 4μV OFFSET INPUT OFFSET VOLTAGE (5mV/DIV) 5 4μV OFFSET 0 –5 GAIN = 160 GAIN = 80 GAIN = 80 –10 VCC = 2.7V VCC = 5V 0 0.05 0.10 0.15 0.20 07451-012 07451-011 VCC = 2.7V VCC = 5V 0 0.2 0.4 0.6 TIME (ms) 0.8 1.0 1.2 1.4 07451-010 –15 –0.05 TIME (ms) Figure 10. Input Offset Voltage vs. Turn-On Time, Filter = 500 Hz 1000 Figure 13. Input Offset Voltage vs. Turn-On Time, Filter = 10 kHz NOISE (nV/ Hz) 100 GAIN = 160 GAIN = 80 10 0.1 1 10 100 1k 10k 100k 07451-009 TIME (10s/DIV) FREQUENCY (Hz) Figure 11. Voltage Noise Density 160 140 120 Figure 14. 0.01 Hz to 10 Hz Voltage Noise 0.30 0.25 VCC = 2.7V, 5V G = 80, 160 GAIN = 160 0.20 0.15 10kHz FILTER 50mV/DIV PSR (dB) 100 GAIN = 80 80 60 0.10 0.05 0 –0.05 40 20 10 500Hz FILTER 10kHz FILTER 100 1k FREQUENCY (Hz) 10k 100k 07451-024 –0.10 –0.15 500Hz FILTER 1ms/DIV Figure 12. Power Supply Rejection (PSR) vs. Frequency Figure 15. Small Signal Step Response Rev. 0 | Page 8 of 16 07451-025 1 0.01 VOLTAGE NOISE (200nV/DIV) AD8293G80/AD8293G160 VCC = 2.7V G = 80, 160 VCC = 5V G = 80, 160 500mV/DIV 10kHz FILTER 1V/DIV 500Hz FILTER 07451-013 10kHz FILTER 500Hz FILTER 07451-017 1ms/DIV 1ms/DIV Figure 16. Large Signal Step Response Figure 17. Large Signal Step Response Rev. 0 | Page 9 of 16 AD8293G80/AD8293G160 THEORY OF OPERATION The AD8293G80/AD8293G160 are precision current-mode correction instrumentation amplifiers capable of single-supply operation. The current-mode correction topology results in excellent accuracy. Figure 18 shows a simplified diagram illustrating the basic operation of the AD8293G80/AD8293G160 (without correction). The circuit consists of a voltage-to-current amplifier (M1 to M6), followed by a current-to-voltage amplifier (R2 and A1). Application of a differential input voltage forces a current through External Resistor R1, resulting in conversion of the input voltage to a signal current. Transistor M3 to Transistor M6 transfer twice this signal current to the inverting input of the op amp A1. Amplifier A1 and External Resistor R2 form a current-to-voltage converter to produce a rail-to-rail output voltage at VOUT. Op amp A1 is a high precision auto-zero amplifier. This amplifier preserves the performance of the autocorrecting, current-mode amplifier topology while offering the user a true voltage-in, voltage-out instrumentation amplifier. Offset errors are corrected internally. An external reference voltage is applied to the noninverting input of A1 to set the output reference level. External Capacitor C2 is used to filter out correction noise. HIGH PSR AND CMR Common-mode rejection and power supply rejection indicate the amount that the offset voltage of an amplifier changes when its common-mode input voltage or power supply voltage changes. The autocorrection architecture of the AD8293G80/AD8293G160 continuously corrects for offset errors, including those induced by changes in input or supply voltage, resulting in exceptional rejection performance. The continuous autocorrection provides great CMR and PSR performances over the entire operating temperature range (−40°C to +85°C). The parasitic resistance in series with R2 does not degrade CMR, but causes a small gain error and a very small offset error. Therefore, an external buffer amplifier is not required to drive VREF to maintain excellent CMR performance. This helps reduce system costs over conventional instrumentation amplifiers. 1/f NOISE CORRECTION Flicker noise, also known as 1/f noise, is noise inherent in the physics of semiconductor devices and decreases 10 dB per decade. The 1/f corner frequency of an amplifier is the frequency at which the flicker noise is equal to the broadband noise of the amplifier. At lower frequencies, flicker noise dominates, causing large errors in low frequency or dc applications. Flicker noise is seen effectively as a slowly varying offset error, which is reduced by the autocorrection topology of the AD8293G80/AD8293G160. This allows the AD8293G80/ AD8293G160 to have lower noise near dc than standard low noise instrumentation amplifiers. VCC C2 I R1 I – IR1 IR1 = VINP M1 (VINP – VINN) R1 M2 VINN M3 M4 I M5 M6 I – IR1 I + IR1 VBIAS A1 VREF 2IR1 R3 C3 07451-020 R2 VOUT = VREF + 2R2 R1 VINP – VINN 2I 2I EXTERNAL Figure 18. Simplified Schematic Rev. 0 | Page 10 of 16 AD8293G80/AD8293G160 APPLICATIONS INFORMATION OVERVIEW The AD8293G80/AD8293G160 reduce board area by integrating filter components, such as Resistors R1, R2, and R3, as shown in Figure 19. Two outputs are available to the user: OUT (Pin 6) and ADC OUT (Pin 4). The difference between the two is the inclusion of a series 5 kΩ resistor at ADC OUT. With the addition of an external capacitor, C3, ADC OUT forms a second filter, comprising of the 5 kΩ resistor and C3, which can be used as an ADC antialiasing filter. In contrast, OUT is the direct output of the instrumentation amplifier. When using the antialiasing filter, there is slightly less switching ripple at ADC OUT than when obtaining the signal directly from OUT. +5V 0.1µF 7 5 +5V 0.1µF 7 5 C2 OUTPUT 6 +VS FILT R2 OUT 8 +IN R1 4kΩ IN-AMP R3 5kΩ ADC OUT 4 1 –IN GND REF 2 3 AD8293Gxx 0.1µF VOLTAGE REFERENCE 07451-022 1µF C2 680pF 0.1µF 6 +VS +IN R1 4kΩ 1 FILT R2 320kΩ IN-AMP OUT Figure 20. Operating on a Single Supply Using an External Voltage Reference (The Output Can Be Used Without an Antialiasing Filter if the Signal Bandwidth Is