RATIOMETRIC VOLTAGE TRANSMITTER AM417 FEATURES GENERAL DESCRIPTION • Supply Voltage 5V± ±5% (Ratio Range) • Wide Operating Temperature Range: –40°C...+100°C • 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 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− 9R VCC IBR 2 OP VCC 8 1R 4 IA Output Stage 5 RB 7 3 6 VOUT VR 1 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 99 1/6 Rev. 2.1 RATIOMETRIC VOLTAGE TRANSMITTER AM417 ELECTRICAL SPECIFICATIONS Tamb = 25°C, VCC = 5V (unless otherwise noted) Parameter Symbol Voltage Range (Ratio Range) VCC Maximum Supply Voltage VCCmax Quiescent Current ICC Conditions Min. Typ. Max. Unit 4.75 5 5.25 V RRB = 500Ω, IIB = 1mA 6 V 6.2 mA °C Temperature Specifications Operating Tamb –40 100 Storage Tst –55 125 °C Junction TJ 150 °C Thermal Resistance Θja DIL8 plastic package 110 °C/W Θja SO8 plastic package 180 °C/W ratiometric with VCC, VVCC = 5V 0.5 V Ratiometric Current Source – Transducer Internal Sense Voltage VRB Output Current Range IIB Output Current IIB ratiometric with VCC, RRB = 500Ω, VVCC = 5V Ratiometric Error RAT@IB IRB vs. Temperature 0.50 1.25 mA 1.02 mA VVCC = 5.25V, RAT@IB = 1.05 VRB (VVCC = 5V) – VRB (VVCC = 5.25V) ±1 mV dIRB/dT IIB = 1mA ±20 ppm/°C Output Voltage Range VIB IIB = 1.25mA 1.5 Output Resistance RIB IIB = 1mA, RIB = ∆UIB/∆IIB, VVIB = 5V, IIB = 1mA 1.5 4.5 MΩ Power Supply Rejection Ratio ∆IIB ∆VCC = 4.75V – 5.25V, VVIB = 5V, IIB = 1mA 76 90 dB 0.98 1 VCC–0.5 V Instrumentation Amplifier Input Voltage Range VIN+;– Internal Gain GIA 1.5 Common Mode Rejection Ratio Power Supply Rejection Ratio Offset Voltage VOS ±3 mV VOS vs. Temperature dVOS/dT ±10 µV/°C Input Bias Current IB Output Voltage Range VVIA Output Resistance ROUT VIN– = 2V, ∆VIN = 200mV GIA = ∆VVIA/∆VIN VCC–2 V 9.8 10.0 CMRR 80 90 dB PSRR 74 80 dB VIN = 2V 25 0 75 nA VCC–2 V 0.1 % FS 20 ∆VIN = 200mV, ideal input Nonlinearity 10.2 kΩ Voltage Output Stage Adjustable Gain GOUT 2 Input Voltage Range VVR Power Supply Rejection Ratio PSSR Offset Voltage VOS VOS vs. Temperature dVOS/dT ∆VIN = 50mV Input Current IIN ∆VIN = 50mV Output Voltage Range VOUT with transistor BCW68H IOUT = 10mA (see figure 5) 11 0 –72 analog microelectronics VCC–2.5 –90 20 0.5 V dB ±3.0 mV ±15 µV/°C 75 nA 4.5 V April 99 2/6 RATIOMETRIC VOLTAGE TRANSMITTER Parameter Symbol Conditions Min. Typ. AM417 Max. Unit Voltage Output Stage (cont.) Output Current IOUT with transistor BCW68H 12.5 mA Output Current Pin VOUT IVOUT pin VOUT 100 200 300 µA Current Limitation Threshold VTHRESH VTHRESH = VVCC – VVOUTmin, R2 = 27Ω, IOUT ≈ 14mA 120 150 180 mV VTHRESH vs. Temperature dVTHRESH /dT –40...+100°C 1.00 1.15 mV Output Resistance ROUT virtual Linearity 0.1 ideal input 0.85 Ω 0.01 %FS Max. Unit 1000 Ω 2.0 kΩ BOUNDARY CONDITIONS Parameter Symbol Resistor Adjustment Current Source (Transducer) Conditions R1 Min. 400 R3 + R4 Gain Resistor Sum Typ. Capacitor Power Supply C1 100 Capacitor Frequency Compensation (Output Stage) C2 4.3 5.8 nF Capacitor Load (Output Stage) C3 1.0 10.0 nF Resistor Sense Current Limitation R2 0 50 Ω nF FUNCTIONAL DIAGRAM VS IBR (ratriometrical) GAIN = 20...110 AMP VOUT Ground Figure 2 analog microelectronics April 99 3/6 RATIOMETRIC VOLTAGE TRANSMITTER AM417 FUNCTIONAL DESCRIPTION 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 = 0Ω). 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 AM417 PINOUT PIN GND 1 8 VCC IB 2 7 VOUT RB 3 6 VR IN+ 4 5 IN− Figure 3 NAME DESIGNATION 1 GND IC Ground 2 IB Output Current Source 3 RB Adjustment Current Source 4 IN+ Input Positive 5 IN– Input Negative 6 VR Adjustment Gain Output Stage 7 VOUT Out Output Stage 8 VCC Supply Voltage 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 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 8 1 4 Figure 4 analog microelectronics April 99 5/6 RATIOMETRIC VOLTAGE TRANSMITTER AM417 APPLICATION FOR OUTPUT VOLTAGE 0.5...4.5V AM417 RTCO1 2 RTCO2 RS RS RS RS 9R IBR OP VS 8 1R Output Stage 4 VIN VCC IA C1 T1 7 VOUT C2 5 RO2 R2 R3 RO1 C3 RTCS 3 6 1 R1 R4 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 Description T1 BCW68H, BC557C (or similar) R1 IBR = 1 mA R2 IOUT = 10mA min (100°C) R3 R4 RS RTCS RO1, RO2 RTCO1, RTCO2 Value Unit low drop, high β at10mA PNP 500 Ω 15 Ω Span (Gain adjustment) 500 Ω VOUT = R3 / (R3 + R4) G 1.5 kΩ typical transducer resistor 3.0 (typ.) kΩ TC span compensation 10 – 120 kΩ Offset adjustment 0 – 500 Ω 0.1 – 10.0 MΩ 330 nF } TC offset adjustment C1 C2 ± 10% 4.7 nF C3 ± 10% 1.0 nF 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