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High Precision Instrumentation Amplifier
FEATURES
* * * * * * * * * Very Low Offset Voltage: < 25V Low Input Bias Current: 5nA High Input Sensitivity High CMRR: > 90dB min Wide Operating Temperature Range: -40C...+140C 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 25V (1V/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 = 25C (unless otherwise noted)
Parameter Supply Voltage Range Maximum Supply Voltage Quiescent Current Temperature Specifications Life Time Operating LT Tamb T85% = 100C for 85% of LT T15% = 120C for 15% of LT Tmax = 140C 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 ja ja 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 V V V/C V/C 5 20 25 60 nA pA/C nA pA/C nV/Hz VPP pA/Hz pAPP VCC - 1.25 V A A 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 A A
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 V/C nA pA/C mV V nF V/s 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 k k k k k k
19 1 75.0 7 VCC = 5V 7 76.8 78.7 13 35
k k mV
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

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