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| Datasheet File OCR Text: |
| Zero Drift, Digital Programmable Instrumentation Amplifier Preliminary Data Sheet FEATURES Digitally programmable gain G= 1, 2, 4, 8, 16, 32, 64, 128 Software or pin programmable Excellent temperature performance Specified from -40C to +125C 50 nV/C max input offset drift 10 ppm/C max gain drift Excellent dc performance 122 dB min CMR, G = 128 25 V max input offset voltage 100 pA max bias current 0.7 uV p-p (0.1 Hz to 10 Hz) Good ac performance Gain Bandwidth Product 1 MHz Slew Rate 0.7 V/s Rail-to-rail input and output Shutdown/Multiplex Additional uncommitted op amp Supply range: 3.0V to 5.5V WR A0 A1 A2 SDN AD8231 OUT2 -IN N P OUT1 +IN AD8231 +VS -VS REF Figure 1. AD8231 Functional Diagram APPLICATIONS Pressure and Strain Transducers Thermocouples and RTDs Programmable Instrumentation Industrial Controls Weigh Scales GENERAL DESCRIPTION The AD8231 is a low drift, rail to rail, instrumentation amplifier with software programmable gains of 1, 2, 4, 8, 16, 32, 64 or 128. The gains are programmed via digital logic or pin strapping. The AD8231 is ideal for applications that require precision performance over a wide temperature range, such as industrial temperature sensing and data logging. Because the gain setting resistors are internal, maximum gain drift is only 10 ppm/C. Because of the autozero input stage, maximum input offset is 25 uV and maximum input offset drift is just 50 nV/C. CMRR is also guaranteed over temperature: 80 dB for G=1, increasing to 122 dB at a gain of 128. Voltage noise is just 0.7 uV p-p (0.01 Hz to 10 Hz). Rev. PrC 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. The AD8231 also includes an uncommitted op amp which can be used for additional gain, differential signal driving or filtering. Like the in amp, the op amp has an autozero architecture, rail to rail input, and rail to rail output. The AD8231 includes a shutdown feature that reduces current to 1 uA and makes the amplifier output high impedance. This allows easy multiplexing of multiple amplifiers without additional switches. The AD8231 is specified over the extended industrial temperature range of -40C to +125C. It is available in a 4mm x 4mm 16-Lead LFCSP (Chip Scale) package. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.326.8703 (c) 2007 Analog Devices, Inc. All rights reserved. AD8231 SPECIFICATIONS Table 1. VS = 5 V, VREF = 2.5 V, G=1, RL = 10 k, -40C TA +125C unless otherwise noted). Parameter INSTRUMENTATION AMPLIFIER OFFSET VOLTAGE Input Offset, VOSI Average Temperature Drift Output Offset, VOSO Average Temperature Drift INPUT CURRENTS Input Bias Current Input Offset Current GAINS Gain Error G=1 G = 2 to 128 Gain Drift G=1 G = 2 to 128 Gain Nonlinearity G= 1 G= 8 G= 128 CMRR G=1 G=2 G=4 G=8 G=16 G=32 G=64 G=128 NOISE Input Voltage Noise, eni Conditions VOS RTI = VOSI + VOSO/G Min Preliminary Data Sheet Typ Max Unit 5 0.01 15 0.02 TA = 25C TA = 25C 1, 2, 4, 8, 16, 32, 64, 128 0.1 1 2 2 VOUT = 0.1 to 4.9V 5 TBD TBD 80 86 92 98 104 110 116 122 Noise RTI = sqrt(eni2 + (eno/G)2 VIN+, VIN- =2.5V ; TA = 25C f = 1 kHz, f = 0.1 Hz to 10 Hz f = 0.01 Hz to 1 Hz f = 1 kHz f = 0.1 Hz to 10 Hz f = 0.01 Hz to 1 Hz Common Mode Differential 100 0.05 100 106 112 118 124 130 136 142 200 50 25 0.05 50 0.1 400 1 100 0.5 V V/C V V/C pA nA pA nA 0.3 TBD 10 10 % % ppm/C ppm/C ppm ppm ppm dB dB dB dB dB dB dB dB Output Voltage Noise, eno 32 0.7 0.2 60 1 0.5 10||5 10||5 110 4.95 10||10 0.05 4.95 nV/Hz V p-p V p-p nV/Hz V p-p V p-p G||pF G||pF dB V G||pF V OTHER INPUT CHARACTERISTICS Differential Input Impedance Common Mode Input Impedance Power Supply Rejection Ratio Input Operating Voltage Range REFERENCE INPUT Input Impedance Voltage Range Rev. PrC | Page 2 of 8 Preliminary Data Sheet DYNAMIC PERFORMANCE Gain Bandwidth Product Slew Rate OUTPUT CHARACTERISTICS Output Voltage High Output Voltage Low Short-Circuit Current DIGITAL INTERFACE Input Voltage Low Input Voltage High Leakage Current Setup Time : tDS Hold Time: tDH Write Width: tCS Gain switching time OPERATIONAL AMPLIFIER INPUT CHARACTERISTICS Offset Voltage, VOS Temperature Drift Input Bias Current Input Offset Current Input Voltage Range Open Loop Gain Common-Mode Rejection Ratio Power Supply Rejection Ratio Voltage Noise Density Voltage Noise DYNAMIC PERFORMANCE Gain Bandwidth Product Slew Rate OUTPUT CHARACTERISTICS Output Voltage High Output Voltage Low Short-Circuit Current BOTH AMPLIFIERS POWER SUPPLY Quiescent Current Quiescent Current (Shutdown) SHD high to high output impedance SHD low to low output impedance Shutdown output impedance AD8231 1 0.6 RL = 100k to ground RL = 10k to ground RL = 100k to 5V RL = 10k to 5V 4.9 4.8 4.94 4.88 60 80 20 MHz V/s V V mV mV mA V V nA ns ns ns ns 100 200 10 1.0 4.0 TBD TBD TBD TBD TBD TA = 25C TA = 25C 0.05 TBD 100 100 f = 0.1 Hz to 10 Hz 10 0.01 200 50 30 0.05 400 1 100 0.5 4.95 110 110 17 0.4 TBD TBD V uV/C pA nA pA nA V V/mV dB dB nV/Hz V p-p 1 0.6 RL = 100k to ground RL = 10k to ground RL = 100k to 5V RL = 10k to 5V 4.9 4.8 4.96 4.92 60 80 20 MHz V/s V V mV mV mA 100 200 10 3.5 1 TBD TBD TBD 4.5 10 mA uA ns ns G||pF Rev. PrC | Page 3 of 8 AD8231 Table 2. VS = 3.3 V, VREF = 1.65 V, -40C TA +125C, G=1, RL = 10 k, unless otherwise noted). Parameter INSTRUMENTATION AMPLIFIER OFFSET VOLTAGE Input Offset, VOSI Average Temperature Drift Output Offset, VOSO Average Temperature Drift INPUT CURRENTS Input Bias Current Input Offset Current GAINS Gain Error G= 1 G= 2 to 128 Gain Drift G= 1 G= 2 to 128 Gain Nonlinearity G= 1 G= 8 G= 128 CMRR G=1 G=2 G=4 G=8 G=16 G=32 G=64 G=128 NOISE Input Voltage Noise, eni Conditions VOS RTI = VOSI + VOSO/G Min Preliminary Data Sheet Typ Max Unit 5 0.01 15 0.02 TA = 25C TA = 25C 1, 2, 4, 8, 16, 32, 64, 128 0.1 1 2 2 0.1 to 3.2V TBD TBD TBD 80 86 92 98 104 110 116 122 Noise RTI = sqrt(eni2 + (eno/G)2 VIN+, VIN- =2.5V; TA = 25C f = 1 kHz f = 0.1 Hz to 10 Hz f = 0.01 Hz to 1 Hz f = 1 kHz f = 0.1 Hz to 10 Hz f = 0.01 Hz to 1 Hz Common Mode Differential 100 0.05 100 106 112 118 124 130 136 142 200 5 25 0.05 50 0.1 400 1 100 0.5 V nV/C V V/C pA nA pA nA 0.3 TBD 10 10 % % ppm/C ppm ppm ppm dB dB dB dB dB dB dB dB Output Voltage Noise, eno 45 0.7 0.2 60 1 0.5 10||5 10||5 110 3.25 10||10 0.05 3.25 nV/Hz V p-p V p-p nV/Hz V p-p V p-p G||pF G||pF dB V G||pF V OTHER INPUT CHARACTERISTICS Differential Input Impedance Common Mode Input Impedance Power Supply Rejection Ratio Input Operating Voltage Range REFERENCE INPUT Input Impedance Voltage Range Rev. PrC | Page 4 of 8 Preliminary Data Sheet DYNAMIC PERFORMANCE Gain Bandwidth Product Slew Rate OUTPUT CHARACTERISTICS Output Voltage High Output Voltage Low Short-Circuit Current DIGITAL INTERFACE Input Voltage Low Input Voltage High Leakage Current Setup Time : tDS Hold Time: tDH Write Width: tCS Gain switching time OPERATIONAL AMPLIFIER INPUT CHARACTERISTICS Offset Voltage, VOS Temperature Drift Input Bias Current Input Offset Current Input Voltage Range Open Loop Gain Common-Mode Rejection Ratio Power Supply Rejection Ratio Voltage Noise Density Voltage Noise DYNAMIC PERFORMANCE Gain Bandwidth Product Slew Rate OUTPUT CHARACTERISTICS Output Voltage High Output Voltage Low Short-Circuit Current BOTH AMPLIFIERS POWER SUPPLY Quiescent Current Quiescent Current (Shutdown) SHD high to high output impedance SHD low to low output impedance Shutdown output impedance AD8231 1 0.6 RL = 100k to ground RL = 10k to ground RL = 100k to 3.3V RL = 10k to 3.3V 3.2 3.1 3.24 3.18 60 80 20 MHz V/s V V mV mV mA V V nA ns ns ns ns 100 200 10 0.7 2.0 TBD TBD TBD TBD TBD TA = 25C TA = 25C 0.05 TBD 100 100 f = 0.1 Hz to 10 Hz 10 0.01 200 50 30 0.05 400 1 100 0.5 3.25 110 110 25 0.4 TBD TBD V uV/C pA nA pA nA V V/mV dB dB nV/Hz V p-p 1 0.6 RL = 100k to ground RL = 10k to ground RL = 100k to 3.3V RL = 10k to 3.3V 3.2 3.1 3.26 3.12 60 80 20 MHz V/s V V mV mV mA 100 200 10 3 1 TBD TBD TBD 4 10 mA uA ns ns G||pF Rev. PrC | Page 5 of 8 AD8231 ABSOLUTE MAXIMUM RATINGS Table 2. AD8231 Absolute Maximum Ratings Parameter Supply Voltage Internal Power Dissipation Output Short Circuit Current Input Voltage (Common-Mode) Differential Input Voltage Storage Temperature Operational Temperature Range Rating Preliminary Data Sheet 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 may affect device reliability. -65C to +150C -40C to +125C A2 16 NC 1 A1 15 A0 14 WR 13 12 +Vs (In-Amp -IN) -INA 2 (In-Amp +IN) +INA 3 NC 4 5 AD8231 Top View 11 GND 10 OUTA (In-Amp Out) 9 REF 6 7 8 SDN +INB -INB OUTB (Op Amp Out) 16-Lead LFCSP (Chip Scale) Package Pin Number 1 Mnemonic NC Function No connect Pin Number 9 Mnemonic REF Function Reference Pin to set the Output Level Output for In Amp 2 -INA Negative Input for Inamp Positive Input for Inamp No connect Shut Down 10 OUTA 3 +INA 11 GND Power Supply Ground 4 5 NC SDN 12 13 +Vs WR Positive Power Supply Write Enable to latch gain setting Gain Setting Bit 6 +INB Positive Input for Undedicated Op Amp Negative Input for Undedicated Op Amp Output for Undedicated Op Amp 14 A0 7 -INB 15 A1 Gain Setting Bit 8 OUTB 16 A2 Gain Setting Bit Rev. PrC | Page 6 of 8 Preliminary Data Sheet GAIN SELECTION The AD8231's gain is set by voltages applied to the A0, A1, and A2 pins. High (HI) or low (LO) voltage limits are listed in the specifications section. To change the gain, the WR pin must be driven low. When the WR pin is driven high, the gain is latched, and voltages at the A0-A2 pins will have no effect. Table 3 is the truth table showing the different gain settings. AD8231 WR LO LO LO LO LO LO LO LO HI A2 LO LO LO LO HI HI HI HI X A1 LO LO HI HI LO LO HI HI X A0 LO HI LO HI LO HI LO HI X Gain 1 2 4 8 16 32 64 128 No change Table 3 Truth table for AD8231's gain settings Rev. PrC | Page 7 of 8 AD8231 Preliminary Data Sheet ESD CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although this product features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality. Rev. PrC | Page 8 of 8 PR06586-0-1/07(PrC) |
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