AM447

High Precision Instrumentation Amplifier FEATURES • • • • • • • • • Very Low Offset Voltage: < 25µV Low Input Bias Current: ≤ 5nA High Input Sensitivity High CMRR: > 90dB min Wide Operating Temperature Range: –40°C...+140°C Adjustable Rail–to–Rail Voltage Output Stage: 0.5...4.5V Single Supply Device (ratiometric) Integrated Source and Sink Capability: ±2mA Low Noise Behaviour AM447 GENERAL DESCRIPTION The AM447 is a high precision amplifier, designed for amplification of sensor bridge signals up to 35mV full scale. The single supply circuit consists of a high precision instrumentation amplifier (IA) and an integrated ratiometric output stage. Input offset voltages less than ±25µV (±1µV/°C) are adjustable by only two externally trimmable resistors. The monitoring of the amplified signal is possible at the output of the IA and makes the adjustment easier. With the externally adjustable gain of the output stage, the AM447 can be used for different signal sources. The 2mA sink and source capability makes it ideal for high precision applications specially in the field of automotive sensors. APPLICATIONS • Small Signal (Bridge) Amplifier Low Pressure Sensors Automotive Applications DMS Interface Interface for Ceramic Sensors • High Precision Amplifier Medical Instrumentation Data Acquisition DELIVERY • DIL16 packages (samples, small quantities) • SO16(n) packages • Dice on 5“ blue foil BLOCK DIAGRAM OC1 OC2 1 2 14 VCC AM447 IN+ 4 IN3 IA 1k Output Stage OUT 10 GAIN 11 19k VCC 7 5 8 6 12 9 RSET VREFIN VREF IAOUT VSET GND Figure 1 analog microelectronics Analog Microelectronics GmbH An der Fahrt 13, D – 55124 Mainz Internet: www.analogmicro.de Phone: +49 (0)6131/91 073 – 0 Fax: +49 (0)6131/91 073 – 30 E–Mail: info@analogmicro.de April 2000 1/6 Rev. 2.1 High Precision Instrumentation Amplifier ELECTRICAL SPECIFICATIONS VCC = 5V, Tamb = 25°C (unless otherwise noted) Parameter Supply Voltage Range Maximum Supply Voltage Quiescent Current Temperature Specifications Life Time Operating LT Tamb T85% = 100°C for 85% of LT T15% = 120°C for 15% of LT Tmax = 140°C for t ≤ 50h 2500/10 –40 Symbol VCC VCCmax ICC VIN = 0 2.2 3.3 Conditions RM yes Min. 4.75 Typ. 5 AM447 Max. 5.25 7 4.6 Unit V V mA h/a 140 °C Storage Junction Thermal Resistance Tst TJ Θja Θja DIL16 plastic package SO16 narrow plastic package –55 70 140 125 150 °C °C °C/W °C/W Instrumentation Amplifier Internal Gain Gain Drift (1) GINT dGIINT /dT VIN CMIR CMRR PSRR VOS VOS DC, RG = 0, VIN = 5mV DC, RG = 0, VIN = 5mV RG = 0, compensated RG = 0, uncompensated RG = 0, compensated RG = 0, uncompensated yes yes yes yes 10Hz 0.1 ... 10Hz VIN = VIN+ – VIN– 100 7 2.1 90 96 102 30 104 ppm/°C 35 mV V dB dB µV µV µV/°C µV/°C ±5 ± 20 ± 25 60 nA pA/°C nA pA/°C nV/√Hz µVPP pA/√Hz pAPP VCC – 1.25 V µA µA 2.9 Differential Input Voltage Common Mode Input Range Common Mode Rejection Ratio Power Supply Rejection Ratio Input Offset Voltage (1) 2.5 ≥ 105 ≥ 105 ± 25 ± 500 ±1 ±5 ±1 ±5 ± 15 ± 50 25 1 1.6 70 VOS vs. Temperature dVOS /dT dVOS /dT Input Offset Current IOS vs. Temperature Input Bias Current IB vs. Temperature Input-Referred Voltage Noise IOS dIOS /dT IB dIB /dT en Input-Referred Current Noise 10Hz 0.1 ... 10Hz Output Voltage Range Output Current VIAOUT IIAOUT Sourcing, VIAOUT = max. Sinking, VIAOUT = min 0.15 50 20 100 End-point Method 20 Capacitive Load Stability Nonlinearity Reference Voltage Adjustable Voltage Range Output Current CIAOUT pF 40 ppm FS VREF IREF Sourcing Sinking yes 0.15 80 80 0.25 1.00 V µA µA Note: RM: RG: FS: (1) No statistic measurements Ratiometrical Generator Source Resistance Full Scale analog microelectronics April 2000 2/6 High Precision Instrumentation Amplifier Parameter Output Stage Adjustable Gain Gain Drift Common Mode Input Range Common Mode Rejection Ratio Power Supply Rejection Ratio Input Offset Voltage VOS vs. Temperature Input Bias Current IB vs. Temperature Output Voltage Range Output Resistance Capacitive Load Stability Slew Rate Sink Capability Source Capability GADJ dGADJ /dT CMIR CMRR PSRR VOS dVOS /dT IB dIB /dT VOUT,min VOUT,max ROUT CLOAD SR ISink ISource CLOAD= 5nF VOUT = 2.5V, GADJ = 1 VOUT = 2.5V, GADJ = 1 yes 0 0.027 Sinking, IOUT = 2mA Sourcing, IOUT = 2mA VCC – 0.2 RG = 0 RG = 0 yes yes –5 5 DC 0.05 80 70 90 80 ± 0.6 ± 15 –10 10 100 1.2 1.65 Symbol Conditions RM Min. Typ. AM447 Max. Unit 4 5 VCC – 1 ppm/°C V dB dB ± 2.8 ± 25 –30 25 200 1 47 mV µV/°C nA pA/°C mV V Ω nF V/µs 2 2 mA mA ESD: This integrated circuit can be damaged by ESD. Analog Microelectronics recommends that all integrated circuits be handled with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage. ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more susceptible to damage because very small parametric changes could cause the device not to meet its published specifications. BOUNDARY CONDITIONS Parameter Offset Compensation Resistor (IA) 1 Offset Compensation Resistor (IA) 2 Gain Resistor 1 Gain Resistor 2 Offset Compensation Resistor (Bridge) 1 Offset Compensation Resistor (Bridge) 2 Set Resistor 2) 3) 1) 1) Symbol ROC1 ROC2 RG1 RG2 RO1 RO2 RSET RBRIDGE VIN Conditions Min. 27 27 67.3 14 Typ. Max. 33 33 68.7 210 Unit kΩ kΩ kΩ kΩ kΩ kΩ kΩ kΩ mV 19 1 75.0 7 VCC = 5V 7 76.8 78.7 13 35 Sensor Bridge Resistor Differential Input Voltage Notes: The offset adjustment is described in the Functional Description. An offset compensation over temperature can only be achieved by choosing the resistors ROC1 and ROC2 with the same temperature coefficient and a very close placement of them in the circuit. 2) A good matching of the resistor RSET with the bridge resistors is forced. 3) The symmetry of the two resistor half bridges has to be better than 2%. 1) analog microelectronics April 2000 3/6 High Precision Instrumentation Amplifier FUNCTIONAL DIAGRAM AM447 ROC1 ROC2 1 2 14 VCC AM447 4 Output Stage IA 10 VOUT RG2 COUT 3 1k 19k 11 VCC 7 R1 R2 RG1 5 8 6 12 9 RSET Ground Figure 2: Application for non-compensated and non-calibrated transducers ROC1 ROC2 1 2 14 VCC AM447 4 IA 3 Output Stage 10 VOUT RG2 COUT 11 1k 19k VCC 7 RG1 5 8 6 12 9 RO1 RSET RO2 Ground Figure 3: Application for compensated and calibrated transducers analog microelectronics April 2000 4/6 High Precision Instrumentation Amplifier FUNCTIONAL DESCRIPTION AM447 The IC AM447 is an integrated high precision amplifier for low bridge output signals. Basically the AM447 is composed of 2 functional sections as shown in Figure 1: 1. A high accuracy instrumentation amplifier (IA) allows amplification with a high signal-to-noise ratio. The two offset compensation resistors ROC1 and ROC2 offer the possibility to make the input offset voltage of the instrumentation amplifier to nearly zero. But offset compensation over temperature is only given if the resistors ROC1 and ROC2 have the same temperature coefficients. Furthermore, these resistors have to be placed together very close. It is also necessary to use similar metals for the connection of the sensor bridge and the AM447 to avoid thermocouple effects. The internal gain of the IA is fixed to the value GINT = 102 . The output voltage VIAOUT (pin 10) of the IA is given by the following equation: VIAOUT = G INT ⋅ (VIN + − VIN − ) + VVREF 2. An output stage de–couples the IA and thus improves the performance of the AM447. The gain factor G is fixed by the two external resistors RG1 and RG2. The gain factor of the output stage is defined by R G ADJ = 1 + G 2 RG1 The output signal VOUT (pin 10) can be calculated with VOUT = G (VIN + − VIN − ) + VVREF = GINT ⋅ G ADJ (VIN + − VIN − ) + 1444 24444 4 3 Span adjustment Offset adjustment for kalibrated transducers VVREF { The AM447 is suited for two types of transducers. The IC is designed for usage with noncompensated and non-calibrated sensors using resistors R1 and R2 for offset calibration as well as for sensor systems with calibrated transducers. The remaining offset of the transducers can be calibrated by variation of VVREF. The adjustment of the offset is then: VVREF = RO 2 VCC RO1 + RO 2 The entire sensor systems realised with the different types of AM447 and only a few external components are shown in Figures 2 and 3. Offset calibration of the instrumentation amplifier The offset compensation has to be handled with care because the entire system performance depends on it. Please note, that this offset adjustment doesn't include the bridge offset. The offset compensation has to be done in the following order: • • • • T = 25° C and VCC = 5V V IN + = V IN − = V REF = 2.5V The voltage between VIAOUT (pin 12) and VREF (pin 6) has to be adjusted to zero Volt. VIAOUT is increased by increasing ROC1 and is decreased by increasing ROC2. analog microelectronics April 2000 5/6 High Precision Instrumentation Amplifier PINOUT PIN NAME OC1 OC2 IN– IN+ RSET VREF GND VREFIN VSET OUT GAIN IAOUT N.C. VCC I.C. I.C. AM447 DESIGNATION Offset Compensation Resistor 1 Offset Compensation Resistor 2 Inverting Input (IA) Non–inverting Input (IA) Set Resistor Reference Voltage Ground Reference Voltage Input Choice of Application Output Gain Adjustment Output (IA) Not Connected Supply Voltage Internally Connected Internally Connected OC1 OC2 IN− IN+ RSET VREF GND VREFIN 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 I.C. I.C. VCC N.C. IAOUT GAIN OUT VSET Figure 4 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 DELIVERY The AM447 is available in version: • 16 pin DIL packages (samples) • SO 16 (n) packages • Dice on 5“ blue foil PINOUT 10,06 ± 0,1 1,45 ± 0,1 0,2 ± 0,05 0,2 ± 0,1 0,42 ± 0,07 1,27 ≤ 0,635 ≥ 0,3 0°-10° 6,2 ± 0,2 4,0 + 0,2 - 0,1 ≤ 2,00 16 1 8 Figure 5 The information provided herein is believed to be reliable; however, Analog Microelectronics assumes no responsibility for inaccuracies or omissions. Analog Microelectronics assumes no responsibility for the use of this information, and all use of such information shall be entirely at the user's own risk. Prices and specifications are subject to change without notice. No patent rights or licences to any of the circuits described herein are implied or granted to any third party. Analog Microelectronics does not authorise or warrant any Analog Microelectronics product use in life support devices and/or systems. analog microelectronics April 2000 6/6