General Description The is a variable-gain precision instrumentation amplifier that combines Rail-to-Rail single-supply operation, outstanding precision specifications, and a high gain bandwidth. This amplifier is also offered in three fixed-gain versions: the MAX95 (), the MAX96 (), and the MAX97 (G = +V/V). The fixed-gain instrumentation amplifiers feature a shutdown function that reduces the quiescent current to 8µA. A traditional three operational amplifier configuration is used to achieve maximum DC precision. The MAX97 have rail-to-rail outputs and inputs that can swing to mv below the negative rail and to within.v of the positive rail. All parts draw only 9µA and operate from a single +.7V to +7.5V supply or from dual ±.5V to ±.75V supplies. These amplifiers are offered in 8-pin SO packages and are specified for the extended temperature range (- C to +85 C). See the MAX98/MAX99 data sheet for single-supply, precision differential amplifiers. Applications Medical Equipment Thermocouple Amplifier ma Loop Transmitters Data-Acquisition Systems Battery-Powered/Portable Equipment Transducer Interface Bridge Amplifier Benefits and Features Low Power Consumption Is Ideal for Remote-Sensing and Battery-Powered Applications +.7V Single-Supply Operation Low Power Consumption 9µA Supply Current 8µA Shutdown Current (MAX95/MAX96/MAX97) Precision Specifications Maximize Sensor Peformance High Common-Mode Rejection: 5dB () Input Common-Mode Range Extends mv Below GND Low 5µV Input Offset Voltage (G +V/V) Low ±.% Gain Error () 5kHz -db Bandwidth (, ) Rail-to-Rail Outputs Ordering Information PART ESA MAX95ESA MAX96ESA - C to +85 C - C to +85 C - C to +85 C 8 SO 8 SO 8 SO MAX97ESA - C to +85 C 8 SO Selector Guide TEMP RANGE PART SHUTDOWN GAIN (V/V) MAX95 MAX96 No Yes Yes Variable + + MAX97 Yes + PPACKAGE CMRR (db) 95 () 95 5 5 Pin Configurations TOP VIEW RG- 8 RG+ 8 SHDN 7 6 MAX95 MAX96 MAX97 7 6 5 5 FB SO SO Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd. 9-68; Rev ; 5/5
Supply Voltage ( to )...+8V All Other Pins... ( +.V) to ( -.V) Current into Any Pin...±mA Output Short-Circuit Duration (to or )... Continuous Continuous Power Dissipation (T A = +7 C) 8-Pin SO (derate 5.9mW/ C above +7 C)... 7mW Operating Temperature Range...- C to +85 C Junction Temperature...+5 C Storage Temperature Range...-65 C to +5 C Lead Temperature (soldering, s)... + C Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Electrical Characteristics ( = +5V, = V, R L = tied to /, V = /, T A = T MIN to T MAX, unless otherwise noted. Typical values are at T A = +5 C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Supply Voltage Range Inferred by PSR test Single supply.7 7.5 Dual supplies ±.5 ±.75 Quiescent Current I CC V = V = /, V DIFF = V 9 µa Shutdown Current I SHDN I SHDN = V IL, M AX 95/M AX 96/M AX 97 onl y 8 µa Input Offset Voltage Input Offset Voltage Drift (Note ) V OS Input Resistance R IN V CM = / Input Capacitance C IN V CM = /, V CM = /, T A = +5 C ± ±5, V CM = /, T A = +5 C ±75 ±5, V CM = /, T A = +5 C ±5 ±5, V CM = /, T A = +5 C ±5, V CM = /, T A = T MIN to T MAX ± ±69 G = + V/V, V C M = V C C /, T A = T M IN to T M AX ±75 ±5 G = + V /V, V C M = V C C /, T A = T M IN to T M AX ±5 ±5 G = + V /V, V C M = V C C /, T A = T M IN to T M AX ±5 ±. ±. TC VOS G +V/V ±.5 ±. Differential Common mode Differential Common mode Input Voltage Range V IN Inferred from CMR test -. -. V V C M = V E E -.V G = +V 66 78 to V C C -.V, T A = + 5 C, G = +V 8 9 DC Common-Mode ΔR S = kω ( N ote ) G = +V 86 99 Rejection CMR DC V C M = V E E -.V G = +V 6 78 to V C C -.V, T A = T M IN to T M AX, G = +V 7 9 ΔR S = kω, ( N ote ) G = +V 77 99 V µv µv/ C MΩ pf db Maxim Integrated
Electrical Characteristics (continued) ( = +5V, = V, R L = tied to /, V = /, T A = T MIN to T MAX, unless otherwise noted. Typical values are at T A = +5 C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS DC Common-Mode Rejection AC Common-Mode Rejection V CM = +.V to -.V, T A = +5 C, ΔR S = kω CMR DC V CM = +.V to -.V, T A = T MIN to T MAX, ΔR S = kω G = +V 78 95 G = +V 9 5 95 5 G = + V /V 5 G = +V 7 95 G = +V 88 5 9 5 G = + V /V 5 CMR AC to -.V, G = +V V CM = +.V G = +V 85 f = Hz G = +V 6 db db Power-Supply Rejection PSR +.7V +7.5V; V CM = +.5V; V = +.5V; V = +.5V; R L = to +.5V;, +V/V, +V/V 9 db Input Bias Current I B V CM = / 6 na Input Bias Current Drift TC IB V CM = / 5 pa/ C Input Offset Current I OS V CM = / ±. ±. na Input Offset Current Drift TC IOS V CM = / 5 pa/ C f = Hz 85 f = Hz 75 nv/ Hz f = khz 7 f =.Hz to Hz. µv RMS f = Hz 5 Input Noise Voltage e n f = Hz nv/ Hz f = khz f =.Hz to Hz.7 µv RMS f = Hz f = Hz nv/ Hz f = khz 8.7 f =.Hz to Hz.6 µv RMS f = Hz. Input Noise Current i n f = Hz.76 pa/ Hz f = khz. f =.Hz to Hz 6 pa RMS Output Voltage Swing V OH, V OL R L = 5kΩ to / - V OH R L = to / V OL - V OH V OL mv Maxim Integrated
Electrical Characteristics (continued) ( = +5V, = V, R L = tied to /, V = /, T A = T MIN to T MAX, unless otherwise noted. Typical values are at T A = +5 C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Short-Circuit Current (Note ) I SC ±.5 ma Gain Equation only + (5kΩ/R G ) Gain Error T A = +5 C, G = +V ±. ±. V CM = /, R L =, G = +V ±. ±. +.V V ±.5 ±.5 -.V G = + V /V, M AX 9 ±.5 T A = +5 C, G = +V ±. ±. V CM = /, R L = 5kΩ, G = +V ±. ±. +.V V ±.5 ±.5 -.V G = + V /V, M AX 9 ±.5 % Gain Temperature /MAX95, ± ±8 Coefficient (Note ) MAX96/MAX97 ± ±5 ppm/ C 5kΩ Resistance Temperature Coefficient (Note ) TC 5kΩ ±6 ppm/ C Nonlinearity +.V V -.V, V CM = /,, +V/V, +V/V, +V/V ±. % Capacitive-Load Stability C L pf -db Bandwidth BW -db V.V P-P, V CM = / 5 MAX95 7 MAX96.5 MAX97..7 Slew Rate SR V = V P-P,.6 V/µs Settling Time t S.%, V = V P-P.5. 5 7 Total Harmonic Distortion THD V = V P-P,, f = khz. % Input Logic Voltage High V IH -.5 V Input Logic Voltage Low V IL -.5 V SHDN Input Current < V SHDN < MAX95/MAX96/ MAX97 only khz ms ±. µa Maxim Integrated
Electrical Characteristics (continued) ( = +5V, = V, R L = tied to /, V = /, T A = T MIN to T MAX, unless otherwise noted. Typical values are at T A = +5 C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Time to Shutdown t SHDN,.%, V = +V MAX95/MAX96/ MAX97 only.5 ms Enable Time From Shutdown t ENABLE,.%, V = +.5V MAX95/MAX96/ MAX97 only.5 ms Power-Up Delay,.%, V = +.5V ms On/Off Settling Time t ON/OFF V SHDN = -.5V to -.5V,,.%, V = +.5V.5 ms Note : Guaranteed by design. Note : Maximum output current (sinking/sourcing) in which the gain changes by less than.%. Note : This specification represents the typical temperature coefficient of an on-chip thin film resistor. In practice, the temperature coefficient of the gain for the will be dominated by the temperature coefficient of the external gain-setting resistor. Typical Operating Characteristics ( = +5V, =, R L = tied to /, T A = +5 C, unless otherwise noted.) NORMALIZED GAIN (db) - - - - -5-6 SMALL-SIGNAL GAIN vs. FREQUENCY k k k M FREQUENCY (Hz) toc- NORMALIZED GAIN (db) - - - - -5-6 MAX95/MAX96/MAX97 SMALL-SIGNAL GAIN vs. FREQUENCY k k k M FREQUENCY (Hz) toc- SETTLING TIME (μs) k k.% SETTLING TIME vs. GAIN (V = Vp-p) k GAIN (V/V) toc Maxim Integrated 5
Typical Operating Characteristics (continued) ( = +5V, =, R L = tied to /, T A = +5 C, unless otherwise noted.) LARGE-SIGNAL PULSE RESPONSE (GAIN = +V/V) toc LARGE-SIGNAL PULSE RESPONSE (GAIN = +V/V) toc5 MAX97 LARGE-SIGNAL PULSE RESPONSE (GAIN = +V/V) toc6 (5mV/div) (5mV/div) (5mV/div) PUT (5mV/div) PUT (5mV/div) PUT (5mV/div) μs/div μs/div μs/div SMALL-SIGNAL PULSE RESPONSE (GAIN = +V/V) toc7 SMALL-SIGNAL PULSE RESPONSE (GAIN = +V/V) toc8 MAX97 SMALL-SIGNAL PULSE RESPONSE (GAIN = +V/V) toc9 (5mV/div) (5μV/div) (5μV/div) PUT (5mV/div) PUT (5mV/div) PUT (5mV/div) μs/div μs/div μs/div PSR (db) - - -6-8 - - - POWER-SUPPLY REJECTION vs. FREQUENCY k k k FREQUENCY (Hz) toc CMR (db) - - -5-6 -7-8 -9 - - COMMON-MODE REJECTION vs. FREQUENCY G = +,V/V - k k k FREQUENCY (Hz) toc Maxim Integrated 6
Typical Operating Characteristics (continued) ( = +5V, =, R L = tied to /, T A = +5 C, unless otherwise noted.) VOLTAGE NOISE DENSITY (nv/ Hz), VOLTAGE-NOISE DENSITY vs. FREQUENCY k k k FREQUENCY (Hz) toc THD + NOISE (%) MAX95/MAX96 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY.... MAX96 MAX95 k k FREQUENCY (Hz) toc SUPPLY CURRENT (μa) SUPPLY CURRENT vs. SUPPLY VOLTAGE 9 toc SUPPLY CURRENT (μa) 98 96 9 9 9 88 SUPPLY CURRENT vs. TEMPERATURE, +V/V toc5 86 SHUTDOWN CURRENT (μa) 8 5 6 7 8 9 SUPPLY VOLTAGE (V) MAX95/MAX96/MAX97 SHUTDOWN CURRENT vs. TEMPERATURE 8 6 toc6 BIAS CURRENT (na) 8 - -5 5 6 85 TEMPERATURE ( C) BIAS CURRENT vs. TEMPERATURE 8 6 TOC7 - -5 5 6 85 TEMPERATURE ( C) - -5 5 6 85 TEMPERATURE ( C) Maxim Integrated 7
Typical Operating Characteristics (continued) ( = +5V, =, R L = tied to /, T A = +5 C, unless otherwise noted.) OFFSET CURRENT (pa) 5-5 - -5 - OFFSET CURRENT vs. TEMPERATURE MAX96 MAX97 - -5 5 6 85 TEMPERATURE ( C) MAX95 TOC8 OFFSET VOLTAGE (μv) 75 5 5-5 -5-75 - OFFSET VOLTAGE vs. TEMPERATURE MAX97 () MAX96 MAX95 - -5 5 6 85 TEMPERATURE ( C) (, ) TOC9 M Pin Description PIN FUNCTION MAX95 MAX96 MAX97 NAME FUNCTION, 8 RG-, RG+ Connection for Gain-Setting Resistor 5 Reference Voltage. Offsets output voltage. Inverting Input Noninverting Input Negative Supply Voltage 5 FB Feedback. Connects to. 6 6 Amplifier Output 7 7 Positive Supply Voltage 8 SHDN Shutdown Control Maxim Integrated 8
Detailed Description Input Stage The MAX97 family of low-power instrumentation amplifiers implements a three-amplifier topology (Figure ). The input stage is composed of two operational amplifiers that together provide a fixed-gain differential and a unity common-mode gain. The output stage is a conventional differential amplifier that provides an overall common-mode rejection of 5dB (G = RG+ Figure. Simplified Block Diagram RG- SHDN R G MAX95 MAX96 MAX97 Figure. MAX95/MAX96/MAX97 Simplified Block Diagram FB +V/V). The s gain can be externally set between +V/V and +,V/V (Table ). The MAX95/MAX96/MAX97 have on-chip gain-setting resistors (Figure ), and their gains are fixed at +V/V, +V/V, and +V/V, respectively. Input Voltage Range and Detailed Operation The common-mode input range for all of these amplifiers is -.V to -.V. Ideally, the instrumentation amplifier (Figure ) responds only to a differential voltage applied to its inputs, and. If both inputs are at the same voltage, the output is V. A differential voltage at (V ) and (V ) develops an identical voltage across the gain-setting resistor, causing a current (I G ) to flow. This current also flows through the feedback resistors of the two input amplifiers A and A, generating a differential voltage of: V - V = I G (R + R G + R ) where V and V are the output voltages of A and A, R G is the gain-setting resistor (internal or external to the part), and R is the feedback resistor of the input amplifiers. I G is determined by the following equation: I G = (V - V ) / R G The output voltage (V ) for the instrumentation amplifier is expressed in the following equation: V = (V - V ) [( R) / R G ] + The common-mode input range is a function of the amplifier s output voltage and the supply voltage. With a power supply of, the largest output signal swing can be obtained with tied to /. This results in an output voltage swing of ± /. An output voltage swing less than full-scale increases the common-mode input range. V I G A V R * R * * R = R = ** R G = INTERNAL TO MAX95/MAX96/MAX97 R G = EXTERNAL TO V - V V R G ** I G R * R * A V V - V R * A R * V = (V - V ) ( R + R G ) Figure. Instrumentation Amplifier Configuration Maxim Integrated 9
Table. External Gain Resistor Selection GAIN (V/V) CLOSEST R G (%) (Ω) *Leave pins and 8 open for. CLOSEST R G (5%) (Ω) + * * + 9.9k 5k +5.k k + 5.6k 5.6k +.6k.7k +5.k.k + 5 5 + 9 +5 +, 9.9 5 +,.9 +5, +,.99 5. V CM vs. V Characterization Figure illustrates the typical common-mode input voltage range over output voltage swing at unitygain (pins and 8 left floating), with a single-supply voltage of = +5V and a bias reference voltage of V = / = +.5V. Points A and D show the full input voltage range of the input amplifiers ( -.V to -.V) since, with +.5V output, there is zero input differential swing. The other points (B, C, E, and F) are determined by the input voltage range of the input amps minus the differential input amplitude necessary to produce the associated V. For the higher gain configurations, the V CM range will increase at the endpoints (B, C, E, and F) since a smaller differential voltage is necessary for the given output voltage. Rail-to-Rail Output Stage The MAX97 s output stage incorporates a common-source structure that maximizes the dynamic range of the instrumentation amplifier. The output can drive up to a (tied to /) resistive load and still typically swing within mv of the rails. With an output load of 5kΩ tied to /, the output voltage swings within mv of the rails. Shutdown Mode The MAX95 MAX97 feature a low-power shutdown mode. When the shutdown pin (SHDN) is pulled low, the internal amplifiers are switched off and the supply current drops to 8µA typically (Figures 5a, 5b, and 5c). This disables the instrumentation amplifier and puts its output in a high-impedance state. Pulling SHDN high enables the instrumentation amplifier. Applications Information Setting the Gain () The s gain is set by connecting a single, external gain resistor between the two RG pins (pin and pin 8), and can be described as: G = + 5kΩ / R G where G is the instrumentation amplifier s gain and R G is the gain-setting resistor. The 5kΩ resistor of the gain equation is the sum of the two resistors internally connected to the feedback loops of the and amplifiers. These embedded feedback resistors are laser trimmed, and their accuracy and temperature coefficients are included in the gain and drift specification for the. COMMON-MODE VOLTAGE (V) 5 /MAX95 = +.5V/+.5V B C A = +5V/+V = T A = +5 C. D.97 5 PUT VOLTAGE (V) Figure. Common-Mode Input Voltage vs. Output Voltage 5μs/div Figure 5a. MAX95 Shutdown Mode F E MAX95 AC-COUPLED (V DIFF = V, ) (5mV/div) SHDN (5V/div) Maxim Integrated
MAX96 AC-COUPLED (V DIFF = mv, ) (5mV/div) R ISO R L C L V R G = () (INTERNAL, MAX95) V V 5μs/div Figure 5b. MAX96 Shutdown Mode SHDN (5V/div) Figure 6a. Using a Resistor to Isolate a Capacitive Load from the Instrumentation Amplifier () MAX97 AC-COUPLED (V DIFF = mv, ) (5mV/div) (5mV/div) SHDN (5V/div) PUT (5mV/div) 5μs/div Figure 5c. MAX97 Shutdown Mode The accuracy and temperature drift of the R G resistors also influence the IC s precision and gain drift, and can be derived from the equation above. With low R G values, which are required for high-gain operation, parasitic resistances may significantly increase the gain error. Capacitive-Load Stability The MAX97 are stable for capacitive loads up to pf (Figure 6a). Applications that require greater capacitive-load driving capability can use an isolation resistor (Figure 6b) between the output and the capacitive load to reduce ringing on the output signal. However, this alternative reduces gain accuracy because R ISO (Figure 6c) forms a potential divider with the load resistor. 5μs/div Figure 6b. Small-Signal Pulse Response with Excessive Capacitive Load (R L =, C L = pf) (5mV/div) PUT (5mV/div) 5μs/div Figure 6c. Small-Signal Pulse Response with Excessive Capacitive Load and Isolating Resistor (R ISO = 75Ω, R L =, C L = pf) Maxim Integrated
Power-Supply Bypassing and Layout Good layout technique optimizes performance by decreasing the amount of stray capacitance at the instrumentation amplifier s gain-setting pins. Excess capacitance will produce peaking in the amplifier s frequency response. To decrease stray capacitance, minimize trace lengths by placing external components as close to the instrumentation amplifier as possible. For best performance, bypass each power supply to ground with a separate.µf capacitor. Transducer Applications The MAX97 instrumentation amplifiers can be used in various signal-conditioning circuits for thermocouples, PTs, strain gauges (displacement sensors), piezoresistive transducers (PRTs), flow sensors, and bioelectrical applications. Figure 7 shows a simplified example of how to attach four strain gauges (two identical two-element strain gauges) to the inputs of the. The bridge contains four resistors, two of which increase and two of which decrease by the same ratio. With a fully balanced bridge, points A () and B () see half the excitation voltage (V BRIDGE ). The low impedance (Ω to 5Ω) of the strain gauges, however, could cause significant voltage drop contributions by the wires leading to the bridge, which would cause excitation variations. Output voltage V can be calculated as follows: V = V AB G where G = ( + 5kΩ / R G ) is the gain of the instrumentation amplifier. Since V AB is directly proportional to the excitation, gain errors may occur. R G ERENCE V BRIDGE R R RG+ V AB = V - V RG- MAX ADC μp A R = Ω - 5Ω R R B Figure 7. Strain Gauge Connection to the Chip Information TRANSISTOR COUNT: Package Information For the latest package outline information and land patterns (footprints), go to /packages. Note that a +, #, or - in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. PACKAGE TYPE PACKAGE CODE LINE NO. LAND PATTERN NO. 8 SO S8-5 - 9-96 Maxim Integrated
Revision History REVISION NUMBER REVISION DATE DESCRIPTION PAGES CHANGED 5/5 Updated Benefits and Features section For pricing, delivery, and ordering information, please contact Maxim Direct at -888-69-6, or visit Maxim Integrated s website at. Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance. Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc. 5 Maxim Integrated Products, Inc.