CURRENT CONVERTER IC AM402 FEATURES GENERAL DESCRIPTION • Wide Supply Voltage Range: 6...35V • Wide Operating Temperature Range: –40°C...+85°C • Adjustable Reference Voltage Source: 4.5 to 10V • Wide Common Mode Range Instrumentation Amplifier • Adjustable Gain and Offset • Two–Wire Output: 4...20mA • Three–Wire Output: 0/4...20mA • Adjustable Output Current Range • Protection Against Reverse Polarity • Current Shutdown with Overvoltage • Shutdown with Excessive Temperature AM402 is a monolithically integrated current converter which has been specially developed for the processing of differential bridge signals. AM402 is suitable for two- and threewire applications and has four function blocks. A high-precision instrumentation amplifier (IA) serves as an input stage. A reference voltage source, which can be adjusted to values of between 4.5 and 10V, excites external components and a voltage-controlled current output stage converts the voltage signal. It is thus possible to generate output currents which correspond to the normal industrial standards (0/4–20mA, 12 ± 8mA). DELIVERY APPLICATIONS • Industrial Process Control • Sensor Signal Converter (e.g. pressure) • Programmable Current Source • DIL16 packages (samples) • SO16(n) packages • Dice on 5“ blue foil BLOCK DIAGRAM GAIN− GAIN GAIN+ 10 11 12 VSET 13 VREF 16 AM402 Reference Voltage 9 1 V Instrumentation Amplifier IN+ 2 3 8 I IN− 14 GND RS+ VCC RS− 5 OUT 7 SET 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 1/8 Rev. 2.1 CURRENT CONVERTER IC AM402 ELECTRICAL SPECIFICATIONS Tamb = 25°C, VCC = 24V, VREF = 5V, IREF = 1mA (unless otherwise noted) Parameter Symbol Voltage Range VCC Quiescent Current ICC Conditions Min. Typ. 6 Tamb = – 40...+85°C, IREF = 0mA Max. Unit 35 V 1.5 mA °C Temperature Specifications Operating Tamb –40 85 Storage Tst –55 125 °C Junction TJ 150 °C Thermal Resistance Θja DIL16 plastic package 70 °C/W Θja SO16 narrow plastic package 140 °C/W VREF VSET not connected 4.75 5.00 5.25 V VREF VSET = GND, VCC ≥ 11V 9.5 10.0 10.5 V Voltage Reference Voltage Trim Range VR10 4.5 VR10 V Current IREF* 0 10 mA VREF vs. Temperature dVREF/dT ±140 ppm/°C Line Regulation Load Regulation ±90 dVREF/dV VCC = 6V...35V 30 80 ppm/V dVREF/dV VCC = 6V...35V, IREF ≈ 5mA 60 150 ppm/V dVREF/dI dVREF/dI Load Capacitance Tamb = – 40...+85°C IREF ≈ 5mA CL 1.9 0.05 0.10 %/mA 0.06 0.15 %/mA 2.2 5.0 µF 1.15 V SET Stage Internal Gain GSET Input Voltage VSET 0.5 Offset Voltage VOS ±0.5 ±2.5 mV VOS vs. Temperature dVOS/dT ±1.6 ±5 µV/°C Input Bias Current IB 8 20 nA IB vs. Temperature dIB/dT 7 18 pA/°C 0 580/GIA mV 0 Instrumentation Amplifier Adjustable Gain GIA Differential Input Voltage Range VIN Common Mode Input Range 1 SET = GND 5 CMIR VCC < 9V 1.5 VCC – 3 V CMIR VCC ≥ 9V 1.5 6.0 V Common Mode Rejection Ratio CMRR 80 90 Power Supply Rejection Ratio PSRR 80 90 dB Offset Voltage VOS ±1 VOS vs. Temperature dVOS/dT ±5 Input Bias Current IB 8 20 nA 6 15 pA/°C dB ±3 mV µV/°C IB vs. Temperature dIB/dT Input Offset Current IOS 0.2 nA IOS vs. Temperature dIOS/dT 0.8 pA/°C Output Voltage Range FS VOUTFS Load Capacitance CL VOUTFS = VGAIN+ – VGAIN– analog microelectronics 400 500 580 mV 250 pF April 99 2/8 CURRENT CONVERTER IC Parameter Symbol Conditions AM402 Min. Typ. Max. Unit V/I Converter Internal Gain GVI 1.00 Trim Range adjustable by R0 0.75 1.00 1.25 400 Voltage Range at R0 FS VR0FS 500 580 mV Offset Voltage VOS β F ≥ 100 ±2 ±6 mV VOS vs. Temperature dVOS/dT β F ≥ 100 ±7 ±20 µV/°C Output Offset Current IOUTOS 3–wire operation –35 –50 µA IOUTOS vs. Temperature dIOUTOS/dT 3–wire operation 55 80 nA/°C Output Offset Current IOUTOS 2–wire operation 14 22 µA IOUTOS vs. Temperature dIOUTOS/dT 2–wire operation 22 35 nA/°C Output Control Current IOUTC 2–wire operation, VR0/100mV 5 IOUTC vs. Temperature dIOUTC/dT 2–wire operation Output Voltage Range VOUT VOUT = RL IOUT, VCC < 16V 0 0 VOUT VOUT = RL IOUT, VCC ≥ 16V Output Current Range FS IOUTFS IOUT = VR0/R0, 3–wire operation Output Resistance ROUT Load Capacitance CL µA –9 nA/°C VCC – 6 10 20 0.5 V mA 1.0 0 V MΩ 500 nF 700 mV Protection Functions Voltage Limitation at R0 Temperature Limitation VLIMR0 VR0 = VIN GIA, SET = GND VLIMR0 VIN = 0, VR0 = VSET/2 TLIMIT 580 640 580 635 690 mV 110 130 150 °C 35 V Protection against reverse polarity Ground vs. VS vs. IOUT Current in case of reverse polarity Ground = 35V, VS = IOUT = 0 3.8 ideal input 0.05 0.15 %FS Typ. Max. Unit mA System Parameters Nonlinearity * In 2–wire operation a maximum current of IOUTmin – ICC is valid Currents flowing into the IC are negative BOUNDARY CONDITIONS Parameter Sense Resistor Stabilisation Resistor Load Resistance Symbol Conditions R0 IOUTFS = 20mA R0 c = 20mA/IOUTFS R5 IOUTFS = 20mA R5 c = 20mA/IOUTFS RL limitation only for 3–wire operation Min. 20 25 29 Ω c ⋅ 20 c ⋅ 25 c ⋅ 29 Ω 35 40 45 Ω c ⋅ 35 c ⋅ 40 c ⋅ 45 Ω 0 500 Ω 25 50 kΩ 200 kΩ 5.0 µF 250 nF Sum Gain Resistors R1 + R2 Sum Offset Resistors R3 + R4 20 C1 1.9 2.2 VREF Capacitance Output Capacitance C2 90 100 D1 Breakdown Voltage VBR only for 2–wire operation 35 50 T1 Forward Current Gain βF 50 150 analog microelectronics V April 99 3/8 CURRENT CONVERTER IC AM402 FUNCTIONAL DIAGRAMS Reference Voltage 3−Wire System VS RA V VIN RIN IA IOUT I RB RL Ground Figure 2 Reference Voltage 2−Wire System VS RA V VIN RIN IA IOUT RB I RL Ground Figure 3 FUNCTIONAL DESCRIPTION AM402 is a monolithically integrated current converter which has been specially developed for the processing of differential bridge signals. By varying a few external components, the output current can be set to various values within a wide range. Only an external output transistor T1 and a diode D1 are needed (See Figure 7 and Figure 8) in addition to the resistors R0 – R5 and the capacitor C1 (C2). The external transistor decreases the power dissipation of the IC and the diode protects the transistor against reverse polarity. The maximum power dissipation of the components must be taken into consideration when selecting the transistor and diode. Typical values for the external components are given in the following Description of Applications. AM402 can principally be used in the implementation of two- and three-wire systems for industrial applications. A schematic diagram illustrates a three-wire system in Figure 2. Here, the differential input voltage (VIN) is shown as a variable resistor. The external reference point Ground is identical to the ground of the IC (GND) and the supply voltage of the IC matches that of the system: VCC = VS. In two-wire configurations, however (Figure 3), the ground of the IC (GND) is connected between resistors R5 and RL. In this instance, the supply voltage of the IC (VCC) is dependent on the supply voltage of the system (VS ) and the value of the load resistor (RL). It can be calculated using the equation: analog microelectronics April 99 4/8 CURRENT CONVERTER IC AM402 VCC = VS − I OUT ⋅ RL AM402 is basically made up of three function blocks (see Figure 1): 1. The amplification of the high-precision instrumentation amplifier as the input stage is adjustable and thus makes applications for a number of input signals and sensors possible. Gain GIA is set via the two external resistors R1 and R2. When selecting the resistors, the sum of R1 + R2 given in the Boundary Conditions must be heeded. When configuring the instrumentation amplifier, the user should ensure that the input signal has the correct polarity. 2. At the voltage-controlled current output an offset current can be set at the output with the help of the internal voltage reference across external resistors R3 and R4 (see the Description of Applications, beginning on page 7). Output current IOUT is provided by external transistor T1 which is driven by the output (IOUT) of the IC. One particular feature of AM402 is that the output current is switched–off if overvoltage occurs on the input side of the device. Another safety feature included in AM402 is the integrated power-down function with excessive temperature. With this, the output current is switched off if the IC gets too warm. 3. The adjustable reference voltage source supplies sensors or other external components with voltage of 5 or 10V (VSET = N.C. or VSET = GND). Additionally, any voltage value between 4.5 and 10V can be set via an external voltage divider. Please note, that Capacitor C1 (ceramic) must also be connected even when the voltage reference is not used. Initial Operation of AM402 To compensate the offset of the output current for the first time, the input must be short-circuited (VIN = 0). In doing so, it should be ensured that the input pins of the instrumentation amplifier have the voltage potentials given in the Electrical Specifications (input voltage range). The short circuit at the input produces an output current IOUT = ISET with I SET (VIN = 0 ) = VREF R4 ⋅ 2R0 R3 + R4 The adjustment of the output current range depends on the choice of external resistors R1 and R2. The maximum output current is defined by the general transfer function of the IC. The following equation is given for the output current IOUT: G I OUT = V IN IA + I SET R0 The gain factor of the instrumentation amplifier G IA = 1 + R1 R2 is determined by the input voltage VIN and the maximum output current IOUTmax. The minimum supply voltage is dependent on the value of the reference voltage. The following applies: VCC ≥ VREF + 1V . VCCmin = 6V RL [Ω] The choice of supply voltage VS also depends on the load resistor RL used by the application. The following inequation determines the minimum supply voltage: VS ≥ I OUTmax RL + VCCmin . The resulting operating range is given in Figure 4. Example calculations and typical values for the external components can be found in the example application shown in the Applications from page 7 onwards. RL ≤ VS − VCCmin IOUTmax RLmax = 500Ω IOUTmax = 20mA 500 300 Operating Area 0 0 6 12 16 24 35 VS [V] Figure 4 analog microelectronics April 99 5/8 CURRENT CONVERTER IC AM402 PINOUT RS+ 1 16 VREF VCC 2 15 N.C. RS− 3 14 GND N.C. 4 13 VSET OUT 5 12 GAIN+ N.C. 6 11 GAIN SET 7 10 GAIN− IN− 8 9 IN+ Figure 5 PIN NAME 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 RS+ VCC RS– N.C. OUT N.C. SET IN– IN+ GAIN– GAIN GAIN+ VSET GND N.C. VREF DESIGNATION Sense Resistor + Supply Voltage Sense Resistor – Not Connected Output Not Connected Set Output Current Input Negative Input Positive Gain Adjustment Gain Adjustment Gain Adjustment Reference Voltage Select IC Ground Not Connected Reference Voltage Output DELIVERY The AM402 is available in version: • 16 pin DIL packages (samples) • SO 16 (n) packages (maximum power dissipation PD = 300mW) • Dice on 5“ blue foil PACKAGE DIMENSIONS SO16 (n) 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 6 analog microelectronics April 99 6/8 CURRENT CONVERTER IC AM402 TYPICAL THREE–WIRE APPLICATION (0/4–20mA) C1 R2 R1 11 10 VREF 12 13 VS 16 AM 402 R0 5/10 V reference 9 VIN 1 V T1 2 IA 3 8 I 14 5 D1 R5 IOUT 7 R3 RL R4 Ground Figure 7 Used in a three–wire circuit, pin 2 (VCC) is connected to pin 1 (RS+) and ground pin 14 (GND) is connected to Ground (Figure 7). The Gain GIA is adjusted by external resistors R1 and R2 and can be calculated by GIA = 1 + R1 R2 ⇒ R1 R2 = GIA − 1 Hence, the transfer–function of the output current IOUT becomes I OUT = VIN GIA R0 + I SET with the current ISET adjusted by external resistors R3 and R4. R3 V R4 VREF I SET = REF ⋅ ⇒ = −1 2 R0 R3 + R4 R4 2 R0 I SET The supply voltage must be chosen with respect to the load resistor RL described by the following equation VS ≥ IOUTmax RL +6V Example 1: Output current range 4...20mA The values of the external devices ( VIN = 0K50 mV , VREF = 5V , GIA = 8 ) are as follows R0 = 25Ω R1 = 33kΩ R2 = 4.7kΩ R3 = 100kΩ R4 = 0...5kΩ R5 = 40Ω RL = 0...500Ω C1 = 2.2µF Example 2: Output current range 0...20mA The values of the external devices ( VIN = 0K250 mV , VREF = 5V , GIA = 2 ) are as follows R0 = 25Ω R1 = 22kΩ R2 = 22kΩ R5 = 40Ω R3, R4 not used (SET = GND) RL = 0...500Ω C1 = 2.2µF analog microelectronics April 99 7/8 CURRENT CONVERTER IC AM402 TYPICAL TWO–WIRE APPLICATION (4–20mA) C1 R2 R1 11 10 VREF 12 13 VS 16 AM 402 R0 5/10 V reference 9 VIN 1 V C2 T1 2 IA 3 8 I 14 5 D1 R5 IOUT 7 R3 RL R4 Ground Figure 8 Used in a two–wire circuit, pin 2 (VCC) is connected to pin 3 (RS–) and ground pin 14 (GND, ⊥) is connected to RL (Figure 8). The Gain GIA is adjusted by external resistors R1 and R2 and can be calculated by GIA = 1 + R1 R2 ⇒ R1 R2 = GIA − 1 Hence, the transfer–function of the output current IOUT becomes I OUT = VIN GIA R0 + I SET with the current ISET adjusted by external resistors R3 and R4. R3 V R4 VREF I SET = REF ⋅ ⇒ = −1 2 R0 R3 + R4 R4 2 R0 I SET The supply voltage must be chosen with respect to the load resistor RL described by the following equation VS ≥ IOUTmax RL +6V Example 3: Output current range 4...20mA The values of the external devices ( VIN = 0K200 mV , VREF = 5V , GIA = 2 ) are as follows R0 = 25Ω R5 = 40Ω R1 = 22kΩ RL = 0...500Ω R2 = 22kΩ C1 = 2.2µF R3 = 100kΩ C2 = 100nF R4 = 0...5kΩ 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 8/8