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RATIOMETRIC VOLTAGE TRANSMITTER
FEATURES
* Supply Voltage 5V5% (Ratio Range) * Wide Operating Temperature Range: -40C...+100C * Ratiometrical Current Source for Transducer Excitation * Instrumentation Amplifier Input * Voltage Output Driver Open Collector: VOUT = 0.5-4.5V IOUT = +10mA * Adjustable Gain, Offset, and Output Voltage Range * Small Package Dimensions: SO8 * Low Cost
AM417
GENERAL DESCRIPTION
The AM417 is a low cost ratiometrical voltage transmitter, designed for flexible bridge input signal conditioning. The IC contains a ratiometric current source for transducer excitation, a high accuracy instrumentation amplifier for differential input signals, and a voltage output driver. Gain, offset, and output voltage range are adjustable by external resistors. The voltage output stage is designed as an open collector stage. The output current is +10mA. A simple current limitation is possible by adding an external resistor. With its functional blocks and possibilities to adjust all important parameters for sensor calibration, the small package dimensions (SO8), and the low costs the AM417 is ideally suited for automotive sensor interface applications.
APPLICATIONS
* Industrial Process Control * Automotive Applications * Sensor Transmitter
DELIVERY
* DIL8 packages (samples) * SOP8 packages * Dice on 5" blue foil
BLOCK DIAGRAM
AM417
IB IN+ IN-
IBR
9R
VCC 8
VCC
2 4 IA 5 3
OP
1R
Output Stage
7
VOUT
RB
6 1 GND
VR
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 99 1/6 Rev. 2.1
RATIOMETRIC VOLTAGE TRANSMITTER
ELECTRICAL SPECIFICATIONS
Tamb = 25C, VCC = 5V (unless otherwise noted)
Parameter Voltage Range (Ratio Range) Maximum Supply Voltage Quiescent Current Temperature Specifications Operating Storage Junction Thermal Resistance Tamb Tst TJ ja ja Ratiometric Current Source - Transducer Internal Sense Voltage Output Current Range Output Current Ratiometric Error VRB IIB IIB RAT@IB ratiometric with VCC, RRB = 500, VVCC = 5V VVCC = 5.25V, RAT@IB = 1.05 VRB (VVCC = 5V) - VRB (VVCC = 5.25V) IIB = 1mA IIB = 1.25mA IIB = 1mA, RIB = UIB/IIB, VVIB = 5V, IIB = 1mA VCC = 4.75V - 5.25V, VVIB = 5V, IIB = 1mA 1.5 1.5 76 4.5 90 ratiometric with VCC, VVCC = 5V 0.50 0.98 1 0.5 DIL8 plastic package SO8 plastic package 110 180 -40 -55 Symbol VCC VCCmax ICC RRB = 500, IIB = 1mA Conditions Min. 4.75 Typ. 5
AM417
Max. 5.25 6 6.2
Unit V V mA
100 125 150
C C C C/W C/W
V 1.25 1.02 1 mA mA mV
IRB vs. Temperature Output Voltage Range Output Resistance Power Supply Rejection Ratio Instrumentation Amplifier Input Voltage Range Internal Gain Common Mode Rejection Ratio Power Supply Rejection Ratio Offset Voltage VOS vs. Temperature Input Bias Current Output Voltage Range Output Resistance Nonlinearity Voltage Output Stage Adjustable Gain Input Voltage Range Power Supply Rejection Ratio Offset Voltage VOS vs. Temperature Input Current Output Voltage Range
dIRB/dT VIB RIB IIB
20 VCC-0.5
ppm/C V M dB
VIN+;- GIA CMRR PSRR VOS dVOS/dT IB VVIA ROUT VIN = 200mV, ideal input VIN = 2V VIN- = 2V, VIN = 200mV GIA = VVIA/VIN
1.5 9.8 80 74 10.0 90 80
VCC-2 10.2
V
dB dB 3 10 mV V/C nA V k 0.1 % FS
25 0 20
75 VCC-2
GOUT VVR PSSR VOS dVOS/dT IIN VOUT VIN = 50mV VIN = 50mV with transistor BCW68H IOUT = 10mA (see figure 5)
2 0 -72 -90
11 VCC-2.5 3.0 15 20 75 4.5 V dB mV V/C nA V
0.5
analog microelectronics
April 99 2/6
RATIOMETRIC VOLTAGE TRANSMITTER
Parameter Voltage Output Stage (cont.) Output Current Output Current Pin VOUT Current Limitation Threshold VTHRESH vs. Temperature Output Resistance Linearity IOUT IVOUT VTHRESH dVTHRESH /dT ROUT with transistor BCW68H pin VOUT VTHRESH = VVCC - VVOUTmin, R2 = 27, IOUT 14mA -40...+100C virtual ideal input 100 120 1.00 0.1 200 150 Symbol Conditions Min. Typ.
AM417
Max. Unit
12.5 300 180 1.15 0.85 0.01
mA A mV mV %FS
BOUNDARY CONDITIONS
Parameter Resistor Adjustment Current Source (Transducer) Gain Resistor Sum Capacitor Power Supply Capacitor Frequency Compensation (Output Stage) Capacitor Load (Output Stage) Resistor Sense Current Limitation Symbol R1 R3 + R4 C1 C2 C3 R2 100 4.3 1.0 0 5.8 10.0 50 Conditions Min. 400 Typ. Max. 1000 2.0 Unit k nF nF nF
FUNCTIONAL DIAGRAM
IBR
VS
(ratriometrical)
GAIN = 20...110 AMP
VOUT
Ground
Figure 2
analog microelectronics
April 99 3/6
RATIOMETRIC VOLTAGE TRANSMITTER
FUNCTIONAL DESCRIPTION
AM417
The AM417 is an integrated low cost ratiometric voltage transmitter specially designed for bridge input signals in automotive applications. With its integrated, ratiometrical current source the AM417 is ideally suited for the signal conditioning of piezoresistive pressure transducers and allows an easy temperature compensation and span adjustment of a these kinds of sensors. The AM417 consists of 3 basic functional blocks: 1. A Ratiometrical Current Source for transducer excitation: The current IIB can be adjusted by the variation of the resistor R1 by the following relation: I IB = VVCC 10 R1
2. An Instrumentation Amplifier Input Stage with a fixed gain GIA = 10 for pre-amplifiing the bridge input signal. 3. An Open Collector Output Stage with the following functions: * Voltage Output: As output is used a voltage amplifier which has an external PNP-open collector stage T1 which is able to push a maximum current of IOUT = 5mA. The gain GOUT is adjustable by the external resistors R3 and R4 between GOUT = 2...11: GOUT = R3 R3 + R4
The gain G of the complete system becomes then G = GIA GOUT. * Current Limitation: A simple clamp stage for the output pin VOUT limits the voltage drop against VCC to VOUT max = VVCC - 15 VBE (T1 ) . . The maximum current can be set by adding a resistor in series to the Emitter of the transistor T1 at the output stage (see figure 4). For the maximum output current is valid: I OUT max = VTRESH - VBE (T1 ) 370mV . R2 R2
If no current limitation is required, the Emitter of the transistor T1 has to be directly connected to VCC (R2 = 0). A proper thermic coupling of the Transistor T1 (VBE-Drift: -2mV/C typ.) and the AM417 reduces the resulting temperature drift of IOUT and increases the performance of the current limitation. Adjustment of Output Voltage Range The span of the output voltage could be adjusted by the gain GOUT of the output stage. The offset of the output voltage can be adjusted in the same way as the adjustment of the sensor offset using the resistors RO1 and RO2 (figure 4).
analog microelectronics
April 99 4/6
RATIOMETRIC VOLTAGE TRANSMITTER
PINOUT
PIN NAME GND IB RB IN+ IN- VR VOUT VCC IC Ground Output Current Source
AM417
DESIGNATION
GND IB RB IN+
1 2 3 4
8 7 6 5
VCC VOUT VR IN-
1 2 3 4
Adjustment Current Source Input Positive Input Negative Adjustment Gain Output Stage Out Output Stage Supply Voltage
Figure 3
5 6 7 8
DELIVERY
The AM417 is available in: * 8 pin DIL packages (samples) * SO 8 packages * Dice on 5" blue foil
PACKAGE DIMENSIONS SOP8
4,98 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
8
1
4
Figure 4
analog microelectronics
April 99 5/6
RATIOMETRIC VOLTAGE TRANSMITTER
APPLICATION FOR OUTPUT VOLTAGE 0.5...4.5V
AM417
RTCO1 RTCO2 2
9R IBR
AM417
VCC 8 C1 R2 T1 C2 R3
VS
OP
1R
RS RS RS RS
4 VIN 5 RO1 3 IA
Output Stage
7
VOUT C3
RO2 RTCS
6 1 R4
R1 Ground
Figure 5 The current application shows the basic functions of the AM417. With the given values of the external components (see List of External Components) the following application features are adjusted: * VIN = 100mV * G = GIA GOUT = 40 * VOUT = 0.5 - 4.5V * IOUT = +10mA - 0.25mA * IBR = 1mA (ratiometrical supply current for the pressure transducer)
LIST OF EXTERNAL COMPONENTS
Symbol T1 R1 R2 R3 R4 RS RTCS RO1, RO2 RTCO1, RTCO2 C1 C2 C3 10% 10% Description BCW68H, BC557C (or similar) IBR = 1 mA IOUT = 10mA min (100C) Value low drop, high at10mA 500 15 500 1.5 3.0 (typ.) 10 - 120 0 - 500 0.1 - 10.0 330 4.7 1.0 Unit PNP k k k M nF nF nF
}
Span (Gain adjustment) VOUT = R3 / (R3 + R4) G
typical transducer resistor TC span compensation Offset adjustment TC offset adjustment
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 99 6/6

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