High Precision Instrumentation Amplifier AM447 FEATURES 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. • • • • 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 APPLICATIONS • Small Signal (Bridge) Amplifier Low Pressure Sensors Automotive Applications DMS Interface Interface for Ceramic Sensors DELIVERY • DIL16 packages (samples, small quantities) • SO16(n) packages • Dice on 5“ blue foil • High Precision Amplifier Medical Instrumentation Data Acquisition BLOCK DIAGRAM OC1 OC2 1 AM447 VCC 14 2 IN+ IA IN- OUT Output Stage 4 10 GAIN 3 11 1k 5 RSET 8 6 12 VREFIN VREF IAOUT 19k 9 VCC 7 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: [email protected] April 2000 1/6 Rev. 2.1 High Precision Instrumentation Amplifier AM447 ELECTRICAL SPECIFICATIONS VCC = 5V, Tamb = 25°C (unless otherwise noted) Parameter Symbol Supply Voltage Range VCC Maximum Supply Voltage VCCmax Quiescent Current ICC Conditions RM Min. Typ. Max. Unit yes 4.75 5 5.25 V 7 V 2.2 3.3 4.6 mA VIN = 0 Temperature Specifications Life Time LT Operating Tamb 2500/10 Storage Tst Junction TJ Thermal Resistance Θja DIL16 plastic package 70 °C/W Θja SO16 narrow plastic package 140 °C/W T85% = 100°C for 85% of LT T15% = 120°C for 15% of LT Tmax = 140°C for t ≤ 50h h/a –40 140 –55 °C 125 °C 150 °C Instrumentation Amplifier Internal Gain Gain Drift GINT (1) 100 dGIINT /dT Differential Input Voltage VIN Common Mode Input Range CMIR Common Mode Rejection Ratio CMRR Power Supply Rejection Ratio PSRR Input Offset Voltage (1) VOS vs. Temperature 102 104 30 VIN = VIN+ – VIN– 7 ppm/°C 35 mV 2.9 V 2.1 2.5 DC, RG = 0, VIN = 5mV 90 ≥ 105 dB DC, RG = 0, VIN = 5mV 96 ≥ 105 dB VOS RG = 0, compensated ± 25 µV VOS RG = 0, uncompensated ± 500 µV dVOS /dT RG = 0, compensated ±1 µV/°C dVOS /dT RG = 0, uncompensated ±5 µV/°C Input Offset Current IOS yes ±1 ±5 nA IOS vs. Temperature dIOS /dT yes ±5 ± 20 pA/°C Input Bias Current IB yes ± 15 ± 25 IB vs. Temperature dIB /dT yes ± 50 Input-Referred Voltage Noise en Input-Referred Current Noise Output Voltage Range VIAOUT Output Current IIAOUT Capacitive Load Stability CIAOUT Nonlinearity nA pA/°C 10Hz 25 0.1 ... 10Hz 1 µVPP 10Hz 1.6 pA/√Hz 0.1 ... 10Hz 70 pAPP 0.15 Sourcing, VIAOUT = max. 50 Sinking, VIAOUT = min 20 60 VCC – 1.25 V µA µA 100 End-point Method nV/√Hz pF 20 40 0.25 1.00 ppm FS Reference Voltage Adjustable Voltage Range VREF Output Current IREF Note: RM: RG: FS: yes 0.15 V Sourcing 80 µA Sinking 80 µA (1) No statistic measurements Ratiometrical Generator Source Resistance Full Scale analog microelectronics April 2000 2/6 High Precision Instrumentation Amplifier Parameter Symbol Conditions RM AM447 Min. Typ. Max. 1.2 1.65 4 Unit Output Stage Adjustable Gain GADJ Gain Drift dGADJ /dT Common Mode Input Range CMIR Common Mode Rejection Ratio CMRR Power Supply Rejection Ratio PSRR Input Offset Voltage VOS RG = 0 VOS vs. Temperature dVOS /dT RG = 0 Input Bias Current IB yes –5 IB vs. Temperature dIB /dT yes 5 Output Voltage Range 5 0.05 DC VCC – 1 80 90 70 VOUT,min Sinking, IOUT = 2mA VOUT,max Sourcing, IOUT = 2mA ppm/°C V dB 80 dB ± 0.6 ± 2.8 mV ± 15 ± 25 µV/°C –10 –30 nA 10 25 pA/°C 100 200 mV VCC – 0.2 V 1 Ω 47 nF Output Resistance ROUT Capacitive Load Stability CLOAD Slew Rate SR CLOAD= 5nF Sink Capability ISink VOUT = 2.5V, GADJ = 1 2 mA Source Capability ISource VOUT = 2.5V, GADJ = 1 2 mA 0 yes 0.027 V/µs 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 Symbol Offset Compensation Resistor (IA) 1 1) ROC1 Offset Compensation Resistor (IA) 2 1) Conditions Min. Typ. 27 Max. Unit 33 kΩ kΩ ROC2 27 33 Gain Resistor 1 RG1 67.3 68.7 kΩ Gain Resistor 2 RG2 14 210 kΩ Offset Compensation Resistor (Bridge) 1 RO1 Offset Compensation Resistor (Bridge) 2 Set Resistor 2) Sensor Bridge Resistor 3) Differential Input Voltage Notes: 19 RO2 1 RSET 75.0 RBRIDGE VIN kΩ VCC = 5V 76.8 kΩ 78.7 kΩ 7 13 kΩ 7 35 mV 1) 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%. analog microelectronics April 2000 3/6 High Precision Instrumentation Amplifier AM447 FUNCTIONAL DIAGRAM ROC1 14 2 1 AM447 VCC ROC2 Output Stage 4 RG2 IA COUT 3 11 1k R1 VOUT 10 R2 5 8 6 19k 9 12 VCC RG1 7 RSET Ground Figure 2: Application for non-compensated and non-calibrated transducers ROC1 14 2 1 AM447 VCC ROC2 Output Stage 4 IA VOUT 10 RG2 COUT 3 11 1k 5 8 6 12 19k 9 VCC RG1 7 RO1 RSET RO2 Ground Figure 3: Application for compensated and calibrated transducers analog microelectronics April 2000 4/6 High Precision Instrumentation Amplifier AM447 FUNCTIONAL DESCRIPTION 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 424444 3 Span adjustment VVREF { Offset adjustment for kalibrated transducers 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 AM447 PINOUT OC1 1 16 I.C. OC2 2 15 I.C. IN− 3 14 VCC IN+ 4 13 N.C. RSET 5 12 IAOUT VREF 6 11 GAIN GND 7 10 OUT VREFIN 8 9 VSET Figure 4 PIN NAME 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 OC1 OC2 IN– IN+ RSET VREF GND VREFIN VSET OUT GAIN IAOUT N.C. VCC I.C. I.C. 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 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 4,0 + 0,2 - 0,1 1,45 ± 0,1 ≤ 2,00 0,2 ± 0,05 0,2 ± 0,1 ≤ 0,635 1,27 0,42 ± 0,07 ≥ 0,3 0°-10° 6,2 ± 0,2 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