Industrial V/I Converter and Protector IC AM462 PRINCIPLE FUNCTION Conversion of input voltage referenced to ground to output current Integrated protection for IC and external components Integrated, adjustable current/voltage sources for external components VCC = 6...35V Single-ended input voltage AM462 0...VCC-5V VREF = 5/10V IOUT = e.g. 0/4...20mA ICC = up to 10mA TYPICAL APPLICATIONS • • • • • • Adjustable voltage-to-current (V/I) converter Adjustable voltage and current source (supply unit) Voltage regulator with additional functions Industrial protector and output IC for microprocessors (the Frame ASIC concept [1]) Peripheral processor IC For examples of typical applications see Example Applications analog microelectronics Analog Microelectronics GmbH An der Fahrt 13, D – 55124 Mainz Internet: http://www.analogmicro.de Phone: Fax: Email: +49 (0)6131/91 073 - 0 +49 (0)6131/91 073 – 30 [email protected] December2006 1/20 Rev. 2.4 Industrial V/I Converter and Protector IC AM462 CONTENTS CONTENTS 2 FEATURES 3 GENERAL DESCRIPTION 3 BLOCK DIAGRAM 3 ELECTRICAL SPECIFICATIONS 4 BOUNDARY CONDITIONS 6 DETAILED DESCRIPTION OF FUNCTIONS 6 INITIAL OPERATION OF AM462 6 General information on 2- and 3-wire applications and the use of current 6 Setting the output current range 6 Selecting the supply voltage 6 Using OP2 as a current source 6 Using OP2 as a voltage reference 6 POINTS TO NOTE: INITIAL OPERATION OF AM462 6 APPLICATIONS 6 Typical 3-wire application with an input signal referenced to ground 6 Typical 2-wire application with an input signal referenced to ground 6 Application for an input signal with an offset 6 BLOCK DIAGRAM AND PINOUT 6 EXAMPLE APPLICATIONS 6 DELIVERY 6 PACKAGE DIMENSIONS 6 FURTHER READING 6 analog microelectronics Analog Microelectronics GmbH An der Fahrt 13, D – 55124 Mainz Internet: http://www.analogmicro.de Phone: Fax: Email: +49 (0)6131/91 073 - 0 +49 (0)6131/91 073 – 30 [email protected] December2006 2/20 Rev. 2.4 Industrial V/I Converter and Protector IC AM462 FEATURES GENERAL DESCRIPTION • Supply voltage: 6...35V • Wide working temperature range: –40°C...+85°C • Adjustable integrated reference voltage source: 4.5 to 10V • Additional voltage/current source • Adjustable amplification • Adjustable offset • Industrial current output (e.g. 0/4...20mA) • Protection against reverse polarity • Short-circuit protection • Output current limitation • Low-cost device: replaces a number of discrete elements • 2- and 3-wire operation • Individually configurable function modules • RoHS compilant AM462 is a universal V/I converter and amplifier IC with a number of additional functions. The IC basically consists of an amplifier, whose gain can be set externally, and an output stage which can convert voltage signals referenced to ground to industrial current signals. An additional reference voltage source for the supply of external components is also included in the device. A further operational amplifier can be connected up as a current source, voltage reference or comparator. One of the main features of the IC is its integrated protective circuitry. The device is protected against reverse polarity and has a built-in output current limit. Converter IC AM462 enables industrial current loop signals (e.g. of 0/4–20mA) to be produced relatively easily. Using the Frame ASIC concept [1] the IC can be connected up to a processor for signal correction. BLOCK DIAGRAM VSET VREF SET 16 15 13 CVREF AM462 CVSET 1 I 2 OP2 11 10 Voltage Reference 9 VBG V INP 8 3 RS+ VCC RSIOUT OP1 4 INN 5 OUTAD 6 GND INDAI 14 Figure 1: Block diagram of AM462 (individually configurable function modules) analog microelectronics Analog Microelectronics GmbH An der Fahrt 13, D – 55124 Mainz Internet: http://www.analogmicro.de Phone: Fax: Email: +49 (0)6131/91 073 - 0 +49 (0)6131/91 073 – 30 [email protected] December2006 3/20 Rev. 2.4 Industrial V/I Converter and Protector IC AM462 ELECTRICAL SPECIFICATIONS Tamb = 25°C, VCC = 24V, VREF = 5V, IREF = 1mA (unless otherwise stated); currents flowing into the IC are negative. Parameter Symbol Supply Voltage Range VCC Quiescent Current ICC Conditions Min. Typ. 6 Tamb = - 40...+85°C, IREF = 0mA Max. Unit 35 V 1.5 mA 85 °C Temperature Specifications Operating Tamb -40 Storage Tst -55 Junction TJ 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 VREF10 VSET = GND, VCC ≥ 11V 9.5 10.0 10.5 V 125 °C 150 °C Voltage Reference Voltage Trim Range VREFADJ Current IREF* VREF vs. Temperature dVREF/dT Tamb = - 40...+85°C Line Regulation dVREF/dV VCC = 6V...35V dVREF/dV VCC = 6V...35V, IREF ≈ 5mA Load Regulation VREF10 V 0 10.0 mA ±90 ±140 ppm/°C 30 80 ppm/V 60 150 ppm/V dVREF/dI 0.05 0.10 %/mA 0.06 0.15 %/mA 1.9 2.2 5.0 µF 1.20 1.27 1.35 V ±60 ±140 ppm/°C 0 10 mA IREF ≈ 5mA dVREF/dI Load Capacitance 4.5 CL Current/Voltage Source OP2 Internal Reference VBG VBG vs. Temperature dVBG/dT Tamb = – 40...+85°C Current Source: ICV = VBG/RSET, from Figure 5 Adjustable Current Range ICV* Output Voltage VCV VCC < 19V VBG VCC – 4 V VCV VCC ≥ 19V VBG 15 V Voltage Source: VCV = VBG (1 + R7 / R6), from Figure Adjustable Voltage Range Output Current Load Capacitance 6 VCV VCC < 19V 0.4 VCC – 4 V VCV VCC ≥ 19V 0.4 15 V ICV* Source ICV Sink CL Source mode 0 1 10 mA –100 µA 10 nF Operational Amplifier Gain Stage (OP1) Adjustable Gain GGAIN Input Range IR VCC < 10V 0 VCC – 5 V IR VCC ≥ 10V 0 5 V ±2 mV Power Supply Rejection Ratio PSRR Offset Voltage VOS 1 80 analog microelectronics Analog Microelectronics GmbH An der Fahrt 13, D – 55124 Mainz Internet: http://www.analogmicro.de 90 ±0.5 Phone: Fax: Email: +49 (0)6131/91 073 - 0 +49 (0)6131/91 073 – 30 [email protected] dB December2006 4/20 Rev. 2.4 Industrial V/I Converter and Protector IC AM462 Parameter Symbol Conditions Min. Typ. Max. Unit µV/°C Operational Amplifier Gain Stage (OP1) (cont.) VOS vs. Temperature dVOS/dT ±3 ±7 Input Bias Current IB 10 25 nA IB vs. Temperature dIB/dT 7 20 pA/°C Output Voltage Limitation VLIM Output Voltage Range VOUTAD VCC < 10V 0 VCC – 5 V VOUTAD VCC ≥ 10V 0 VREF V 250 pF Load Capacitance VREF CL V V/I Converter Internal Gain GVI Trim Range Adjustable by R0 0,12 0.125 0,13 0.75 1.00 1.25 Voltage Range at R0 FS VR0FS 750 mV Offset Voltage VOS F ≥ 100 350 ±2 ±4 mV VOS vs. Temperature dVOS/dT F ≥ 100 ±7 ±14 µV/°C Input Resistance RIN 120 160 RIN vs. Temperature dRIN/dT 0.2 0.3 Output Offset Current IOUTOS 3-wire operation –25 –35 µA IOUTOS vs. Temperature dIOUTOS/dT 3-wire operation 16 26 nA/°C Output Offset Current IOUTOS 2-wire operation 9.5 14 µA IOUTOS vs. Temperature dIOUTOS/dT 2-wire operation 6 8 nA/°C Output Control Current IOUTC 2-wire operation, VR0/100mV 6 8 µA IOUTC vs. Temperature dIOUTC/dT 2-wire operation –15 nA/°C Output Voltage Range VOUT VOUT = RL IOUT, VCC < 18V 0 VCC – 6 V VOUT VOUT = RL IOUT, VCC ≥ 18V 0 12 V Output Current Range FS IOUTFS IOUT = VR0/R0, 3-wire operation Output Resistance ROUT Load Capacitance CL –10 0.5 kΩ kΩ/°C 20 mA 1.0 MΩ 0 500 nF SET Stage Internal Gain GSET Input Voltage VSET 0.5 1.15 V Offset Voltage VOS ±0.5 ±1.5 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 635 0 Protection Functions Voltage Limitation at R0 VLIMR0 Protection against reverse polarity Current in the event of reverse polarity VINDAI = 0, VR0 = GSET VSET 690 mV Ground vs. VS vs. VOUT 580 35 V Ground vs. VS vs. IOUT 35 V Ground = 35V, VS = IOUT = 0 4.5 Ideal input 0.05 mA System Parameters Nonlinearity 0.15 %FS * In 2-wire operation a maximum current of IOUTmin – ICC is valid analog microelectronics Analog Microelectronics GmbH An der Fahrt 13, D – 55124 Mainz Internet: http://www.analogmicro.de Phone: Fax: Email: +49 (0)6131/91 073 - 0 +49 (0)6131/91 073 – 30 [email protected] December2006 5/20 Rev. 2.4 Industrial V/I Converter and Protector IC AM462 BOUNDARY CONDITIONS Parameter Symbol Conditions Sense Resistor R0 IOUTFS = 20mA R c = 20mA/IOUTFS Stabilization Resistor R IOUTFS = 20mA R c = 20mA/IOUTFS RL Limitation only for 3-wire operation Load Resistance Sum Gain Resistors R1 + R2 Sum Offset Resistors R3 + R4 Min. Typ. Max. 17 27 38 c ⋅ 17 c ⋅ 27 c ⋅ 38 35 40 45 c ⋅ 35 c ⋅ 40 c ⋅ 45 Unit 0 600 20 200 k 200 k VREF Capacitance C1 Ceramic 1.9 2.2 5.0 µF Output Capacitance C2 Only for 2-wire operation 90 100 250 nF D1 Breakdown Voltage VBR T1 Forward Current Gain F 20 BCX54/55/56, for example 35 50 50 150 V DETAILED DESCRIPTION OF FUNCTIONS AM462 is a modular, universal V/I converter and protector IC which has been specially developed for the conditioning of voltage signals referenced to ground. It is designed for both 2- and 3-wire operation in industrial applications (cf. application in Figure 8). AM462’s various functions are depicted in the block diagram (Figure 2) which also illustrates how few external components are required for the operation of this particular device. AM462 consists of several modular function blocks (operational amplifiers, voltage-to-current converters and references) which, depending on external configurations, can either be switched to one another or operated separately (see the basic circuitry in Figure 2): 1. Operational amplifier stage OP1 enables a positive voltage signal to be amplified. OP1 gain GGAIN can be set via external resistors R1 and R2. Protective circuitry against overvoltage is integrated into the chip, limiting the voltage to the set value of the reference voltage. Output voltage VOUTAD at pin OUTAD is calculated as: VOUTAD = VINP ⋅ GGAIN with GGAIN = 1 + R1 R2 (1) where VINP is the voltage at OP1’s input pin INP. 2. The internal voltage-to-current converter (V/I converter) provides a voltage-controlled current signal at IC output IOUT (pin 8) which activates an external transistor T1; this in turn supplies the actual output current IOUT. To reduce power dissipation the transistor is an external component and protected against reverse polarity by an additional diode D1. Via pin SET an offset current ISET can be set at output IOUT (with the help of the internal voltage reference and an external voltage divider as shown in Figure 2, for example). External resistor R0 permits the output current to be finely adjusted with parallel operation of current and the voltage output. For the output current provided by T1 the following ratio applies: analog microelectronics Analog Microelectronics GmbH An der Fahrt 13, D – 55124 Mainz Internet: http://www.analogmicro.de Phone: Fax: Email: +49 (0)6131/91 073 - 0 +49 (0)6131/91 073 – 30 [email protected] December2006 6/20 Rev. 2.4 Industrial V/I Converter and Protector IC AM462 I OUT = VINDAI V + I SET with I SET = SET 8 R0 2R 0 (2) with VINDAI the voltage at pin INDAI and VSET the voltage at pin SET (V/I converter inputs)1. VREF VCVREF 1 AM462 VCVSET C1 R3 15 13 R4 16 VS VSET I 2 OP2 11 R0 10 Voltage Reference 9 VBG V VINP 8 T1 D1 3 OP1 5 4 R2 6 R1 VOUTAD 14 R5 IOUT VINDAI Ground Figure 2: Block diagram of AM462 with external components (3-wire circuit for current output) 3. The AM462 reference voltage source enables voltage to be supplied to external components (such as sensors, microprocessors, etc.). The reference voltage value VREF can be set via pin 13 VSET. If pin VSET is not connected, VREF = 5V; if VSET is switched to ground, VREF = 10V. Values between the above can be set if two external resistors are used (inserted between pin VREF and pin VSET and between pin VSET and GND; see Figure 2). External (ceramic) capacitor C1 at pin VREF stabilizes the reference voltage. It must be connected even if the voltage reference is not in use. 4. The additional operational amplifier stage OP2 can be used as a current or voltage source to supply external components. OP2's positive input is connected internally to voltage VBG so that the output current or output voltage can be set across a wide range using one or two external resistors. 1 The construction of the V/I converter is such that output current IOUT is largely independent of the current amplification βF of external transistor T1. Production-specific variations in the current amplification of the transistors used are compensated for internally by the V/I converter. analog microelectronics Analog Microelectronics GmbH An der Fahrt 13, D – 55124 Mainz Internet: http://www.analogmicro.de Phone: Fax: Email: +49 (0)6131/91 073 - 0 +49 (0)6131/91 073 – 30 [email protected] December2006 7/20 Rev. 2.4 Industrial V/I Converter and Protector IC AM462 INITIAL OPERATION OF AM462 General information on 2- and 3-wire applications and the use of current In 3-wire operation (cf. Figure 3 right and Figure 7) the ground of the IC (pin GND) is connected up to the external mass of the system Ground. The system's supply voltage VS is connected to pin VCC and pin VCC to pin RS+. In 2-wire operation (cf. Figure 3 left and Figure 7) system supply voltage VS is connected to pin RS+ and pin VCC to RS-. The ground of the IC (pin GND) is connected to the node between resistor R5 and load resistor RL (current output IOUT). IC ground (GND) is not the same as system ground (Ground)!! The output signal is picked up via load resistor RL which connects current output IOUT to the system ground. In 2-wire operation the IC ground is "virtual" (floating), as with a constant load resistance the supply voltage of the device VCC changes according to the current. As a rule, the following equation applies to 2-wire operation: VCC = VS − I OUT (VIN ) RL (2) The reason for this is that in 2-wire operation the IC is connected in series to the actual load resistor RL. This is illustrated in Figure 3. In 3-wire operation VCC = VS, as the IC ground is connected to the ground of the system. 2-wire system signal source and conditioning IC GND ≠ Ground VCC ≠ VS 3-wire system signal source and conditioning IC VCC IOUT GND RL VS GND = Ground VCC = VS Ground IOUT RL VCC = VS Ground = GND Figure 3: The difference between 2- and 3-wire operation Setting the output current range When using amplification stage OP1 together with the V/I converter for voltage-to-current conversion the offset of the output current should first be compensated for by suitable selection of resistors R3 and R4. To this end the OP1 input must be connected to ground (VINP = 0). With the short circuit at the input and by connecting up V/I converter pin VSET as shown in Figure 2 the values of the output current according to Equation 2 are as follows: analog microelectronics Analog Microelectronics GmbH An der Fahrt 13, D – 55124 Mainz Internet: http://www.analogmicro.de Phone: Fax: Email: +49 (0)6131/91 073 - 0 +49 (0)6131/91 073 – 30 [email protected] December2006 8/20 Rev. 2.4 Industrial V/I Converter and Protector IC AM462 I OUT (V INDAI = 0 ) = I SET = V REF R4 ⋅ 2 R 0 R3 + R 4 (3) and thus for the ratio of the resistors R3/R4: R3 VREF = −1 R4 2R0 I SET (4) The output current range is set in conjunction with the selected external resistors R1 and R2 (or fine adjustment with R0 ). Using Equations 1 and 2 the following is calculated for output current IOUT : I OUT = VINP GGAIN R + I SET with GGAIN = 1 + 1 8 R0 R2 (5) Selecting the supply voltage System supply voltage VS needed to operate AM462 is dependent on the selected mode of operation. When using current output pin IOUT (in conjunction with the external transistor) the value of VS is dependent on that of the relevant load resistor RL (max. 600Ω) used by the application. The minimum system supply voltage VS is then: VS ≥ I OUT max RL + VCC min (6) Here, IOUTmax stands for the maximum output current and VCCmin for the minimum IC supply voltage which is dependent on the selected reference voltage: VCC min ≥ VREF + 1V RL [Ω] RL (7) VCCmin = 6V VS − VCCmin IOUTmax RLmax = 600Ω IOUTmax = 20mA 600 300 Working range 0 0 6 12 24 18 35 VS [V] Figure 4: Working range in conjunction with the load resistor analog microelectronics Analog Microelectronics GmbH An der Fahrt 13, D – 55124 Mainz Internet: http://www.analogmicro.de Phone: Fax: Email: +49 (0)6131/91 073 - 0 +49 (0)6131/91 073 – 30 [email protected] December2006 9/20 Rev. 2.4 Industrial V/I Converter and Protector IC AM462 The working range resulting from Equation 6 is described in Figure 4. Example calculations and typical values for the external components can be found in the example applications from page 13 onwards. Using OP2 as a current source The additional operational amplifier OP2 can easily be connected up as a constant current source. Using the circuit in Figure 5 the following applies: OP2 connected as current source IS AM462 1 2 OP2 RSET VBG Figure 5: Using OP2 as a constant current source Example : OP2 as courrent source IS = V BG 1 .27 V = R SET R SET (8) The bridge symbol represents the component to be supplied with current (e.g. a piezoresistive sensing element or temperature sensor). A supply current of IS = 1mA is to be set. Using Equation 8 the following value is calculated for external resistor RSET, which in turn stipulates the size of the current: R SET = V BG 1 .27 V = = 1 .27 k Ω IS 1mA analog microelectronics Analog Microelectronics GmbH An der Fahrt 13, D – 55124 Mainz Internet: http://www.analogmicro.de Phone: Fax: Email: +49 (0)6131/91 073 - 0 +49 (0)6131/91 073 – 30 [email protected] December2006 10/20 Rev. 2.4 Industrial V/I Converter and Protector IC AM462 Using OP2 as a voltage reference In addition to the integrated voltage reference OP2 can also be used to supply voltage to external components, such as A/D converters and microprocessors, for example. Lower voltages can be generated (e.g. 3.3V) which with the increasing miniaturization of devices and need for ever lower levels of power dissipation in digital components is today of growing importance. OP2 connected as voltage reference VCVREF µP AM462 R6 1 2 OP2 R7 VBG Figure 6: Using OP2 as a voltage reference The additional operational amplifier OP2 can easily be connected up as a voltage reference. Using the circuit in Figure 6 the following applies: R V CVREF = V BG 1 + 6 = 1 . 27 V R7 R 1 + 6 R7 (9) Example : OP2 as voltage reference A voltage of VCVREF = 3.3V is to be set. Using Equation 9 the following ratio is calculated for external resistors R6 and R7: R 6 V CVREF = − 1 ≈ 2 , 6 − 1 = 1,6 R7 V BG The following example values are produced for the resistors: R7 = 10kΩ R6 = 16kΩ analog microelectronics Analog Microelectronics GmbH An der Fahrt 13, D – 55124 Mainz Internet: http://www.analogmicro.de Phone: Fax: Email: +49 (0)6131/91 073 - 0 +49 (0)6131/91 073 – 30 [email protected] December2006 11/20 Rev. 2.4 Industrial V/I Converter and Protector IC AM462 POINTS TO NOTE: INITIAL OPERATION OF AM462 1. When operating AM462 it is imperative that external capacitor C1 is always connected (cf. Figure 2). Care must be taken that the value of the capacitance does not lie beyond its given range, even across the range of temperature (see Boundary Conditions on page 7). In 2-wire operation ceramic capacitor C2 must also be used (cf. Figure 8). 2. In a 2-wire setup the power consumption of the overall system (AM462 plus all external components, including the configuration resistors) must not exceed the sum of IOUTmin (usually 4mA). 3. All AM462 function blocks not required by the application must be connected to a defined (and allowed) potential. 4. A load resistance of 600Ω maximum is permitted for the current output. 5. The values of external resistors R0, R1, R2, R3, R4 and R5 must be selected within the permissible range given in the boundary conditions on page 7. APPLICATIONS Typical 3-wire application with an input signal referenced to ground Figure 7 shows a 3-wire application in which AM462 amplifies and converts a positive voltage signal referenced to ground. The unused blocks (e.g. OP2) have been set to defined operating points in the application. Alternatively, these function groups can also be used here (e.g. to supply external components). For output current IOUT the following applies according to Equations 1 and 2: I OUT = VINP ⋅ R GI + I SET with GI = GGAIN = 1 + 1 8 R0 R2 Example: 0…20mA Voltage-To-Current Transmitter To obtain a signal of VINP = 0...1V at the OP1 input the external components are to be dimensioned in such a way that the output current has a range of 0...20mA (i.e. ISET = 0 ⇒ SET = GND). With R0 = 27Ω: I OUT = VINP ⋅ G GI + I SET = VINP ⋅ GAIN 8R0 8 R0 The following then applies to the gain: analog microelectronics Analog Microelectronics GmbH An der Fahrt 13, D – 55124 Mainz Internet: http://www.analogmicro.de Phone: Fax: Email: +49 (0)6131/91 073 - 0 +49 (0)6131/91 073 – 30 [email protected] December2006 12/20 Rev. 2.4 Industrial V/I Converter and Protector IC AM462 3-wire connection C1 1 AM462 16 15 13 VS ISET = 0 I 2 OP2 11 R0 10 Voltage Reference 9 VBG V VINP 8 T1 D1 3 OP1 6 5 4 Single-ended input voltage 14 R5 R1 R2 IOUT RL Ground Connections setting unused function blocks to a defined operating point Figure 7: Typical application for input signals referenced to ground GGAIN = 8R0 I OUT 20mA = 8 ⋅ 27Ω ⋅ ≈ 4.32 ⇒ VINP 1V R1 = 4.32 − 1 = 3.32 R2 Observing the boundary conditions (page 7), the following values are obtained for the external components: R1 ≈ 33.2kΩ R2 = 10kΩ R0 = 27Ω R5 = 39Ω RL = 0...600Ω C1 = 2.2µF Typical 2-wire application with an input signal referenced to ground In 2-wire operation (cf. Figure 8) system supply voltage VS is connected up to pin RS+ and pin VCC to pin RS-. The ground of the IC (pin GND) is connected to the node between resistor R5 and load resistor RL.. IC ground (GND) is not the same as system ground (Ground). The output signal is picked up via load resistor RL which connects current output IOUT to the system ground. It must be ensured that in 2-wire operation an additional current load (use of current/voltage source) is limited to 4mA due to the domestic current supply and limitation. For output current IOUT the following applies according to Equations 1 and 2: I OUT = VINP ⋅ R GI V R4 + I SET with GI = GGAIN = 1 + 1 and I SET = REF ⋅ 8R0 R2 2R0 R3 + R4 analog microelectronics Analog Microelectronics GmbH An der Fahrt 13, D – 55124 Mainz Internet: http://www.analogmicro.de Phone: Fax: Email: +49 (0)6131/91 073 - 0 +49 (0)6131/91 073 – 30 [email protected] December2006 13/20 Rev. 2.4 Industrial V/I Converter and Protector IC AM462 C1 1 AM462 R3 VS 16 15 13 R4 2 OP2 C2 R0 11 I 10 Voltage Reference 9 VBG V VINP 8 T1 D1 3 OP1 2-wire connection 6 5 4 Single-ended input voltage R2 R1 IC ground: GND 14 } System ground: Ground different potentials! R5 IOUT RL GND Ground Connections setting unused function blocks to a defined operating point Figure 8: Typical 2-wire operation for input signals referenced to ground Example : 4…20mA Voltage-To-Current Transmitter To obtain a signal of VINP = 0...1V at the OP1 input the external components are to be dimensioned in such a way that the output current has a range of 4...20mA. The following applies: I OUT = VINP ⋅ G GI + I SET = VINP ⋅ GAIN + 4mA 8 R0 8R0 With R0 = 27Ω and ISET = 4mA Equation 4 produces the following for resistors R3 and R4: R3 VREF 5V = −1 = − 1 ≈ 22.15 2 ⋅27Ω ⋅ 4mA R4 2R0 I SET and thus the following value for the gain: GGAIN = 8R0 I OUT max − I SET 16mA = 8 ⋅ 27Ω ⋅ = 3.456 1V VINP ⇒ R1 = 3.456 − 1 = 2.456 R2 Observing the given boundary conditions, the following values are obtained for the external components: R1 ≈ 24.56kΩ R0 = 27Ω R2 = 10kΩ R5 = 39Ω R3 ≈ 44.3kΩ RL = 0...600Ω R4 = 2kΩ C1 = 2.2µF analog microelectronics Analog Microelectronics GmbH An der Fahrt 13, D – 55124 Mainz Internet: http://www.analogmicro.de Phone: Fax: Email: +49 (0)6131/91 073 - 0 +49 (0)6131/91 073 – 30 [email protected] C2 = 100nF December2006 14/20 Rev. 2.4 Industrial V/I Converter and Protector IC AM462 Application for an input signal with an offset It is not uncommon for input signals to have an offset (e.g. of 0.5...4.5V or 1...6V). For signals such as these an offset current is generated at the IC output also when ISET = 0. The circuit can then be dimensioned as described in the following. According to Equation 2 the following applies for a required current swing at the output of ∆IOUT = IOUTmax – IOUTmin: ∆I OUT = ∆VPIN 6 8R0 ⇒ ∆VPIN 6 = 8R0 ∆I OUT (10) For an input current swing of ∆VIN = VINmax – VINmin the necessary gain is calculated as: G= ∆VPIN 6 ∆VIN (11) If G < 1, the input signal can be routed directly to pin 6 (INDAI) via a voltage divider without OP1 having to be used (see Figure 9). With this circuitry the following results: G= ∆VPIN 6 R9 = ∆VIN R8 + R9 ⇒ ∆VIN R8 = −1 R9 ∆VPIN 6 (12) From input offset VINmin the following output current is then obtained when ISET = 0: I OUT (VIN min ) = VIN min ⋅ R9 1 ⋅ R8 + R9 8R0 (13) Using the SET pin and Equation 2 the required minimum output current IOUTmin can then be set: I OUT = VIN ⋅ R9 1 V R4 ⋅ + I SET with I SET = REF ⋅ 2R0 R3 + R4 R8 + R9 8 R0 (14) Example : 4..20mA Voltage-To-Current Transmitter with Input Signal Offset To obtain a signal of VIN = 0.5...4.5V the external components are to be dimensioned in such a way that the output current has a range of 4...20mA. The circuitry is shown in Figure 9. OP1 is not used here. It is, however, available to the user as an additional OP and can be used as an impedance converter at the voltage-to-current converter input INDAI, for example. With reference to Equation 10 and with R0 = 27Ω, a voltage swing is obtained at pin 6 of: ∆VPIN 6 = 8R0 ∆I OUT = 8 ⋅ 27Ω ⋅16mA = 3.456V Using Equation 12 the following applies: R8 ∆VIN − ∆VPIN 6 4V − 3.456V = = ≈ 0.157 ∆VPIN 6 3.456V R9 ⇒ R9 = 6.35 ⋅R8 analog microelectronics Analog Microelectronics GmbH An der Fahrt 13, D – 55124 Mainz Internet: http://www.analogmicro.de Phone: Fax: Email: +49 (0)6131/91 073 - 0 +49 (0)6131/91 073 – 30 [email protected] December2006 15/20 Rev. 2.4 Industrial V/I Converter and Protector IC AM462 C1 1 AM462 R3 VS 16 15 13 3-wire connection R4 I 2 OP2 11 R0 10 Voltage reference 9 VBG V 8 T1 D1 3 OP1 6 5 4 14 R5 R8 V IN Single-ended input voltage R9 IOUT RL Connections setting unused function blocks in a defined operating point Ground Figure 9: Converting an input signal with an According to Equation 13 the minimum output current generated by the input offset is calculated as: I OUT min = VIN min ⋅ R9 1 6,37 1 ⋅ = 0.5V ⋅ ⋅ ≈ 2mA R8 + R9 8R0 6.37 + 1 8 ⋅ 27Ω To obtain an output current of IOUT = 4...20mA, according to the above a current of ISET = 2mA must then be added. With reference to Equation 4 the ratio of R3 to R4 is calculated thus: ! I SET = 2mA = VREF R4 ⋅ 2R0 R3 + R4 ⇒ R3 VREF 5V = −1 = − 1 ≈ 45.3 2 ⋅ 27Ω ⋅ 2mA R4 2R0 I SET Observing the given boundary conditions, the following values are obtained for the external components: R0 ≈= 27Ω R5 = 39Ω R8 ≈ 10kΩ RL = 0...600Ω R9 = 63.7kΩ C1 = 2.2µF R3 = 90.6kΩ analog microelectronics Analog Microelectronics GmbH An der Fahrt 13, D – 55124 Mainz Internet: http://www.analogmicro.de Phone: Fax: Email: +49 (0)6131/91 073 - 0 +49 (0)6131/91 073 – 30 [email protected] R4 = 2kΩ December2006 16/20 Rev. 2.4 Industrial V/I Converter and Protector IC AM462 BLOCK DIAGRAM AND PINOUT VSET VREF SET 16 15 13 CVREF 1 AM462 CVSET I 2 OP2 11 10 Voltage Reference 9 VBG V INP 8 3 RS+ VCC RSIOUT OP1 5 4 INN 6 OUTAD GND INDAI 14 Figure 10: Block diagram of AM462 PIN NAME 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 CVREF CVSET INP INN OUTAD INDAI N.C. IOUT RS– VCC RS+ N.C. VSET GND VREF SET EXPLANATION Current/Voltage reference Current/Voltage reference set Positive input Negative input System amplification output Current output stage input Not connected Current output Sensing resistor Supply voltage Sensing resistor + Not connected Reference voltage source set IC ground Reference voltage source output Output offset current set CVREF CVSET INP INN OUTAD INDAI N.C. IOUT 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 SET VREF GND VSET N.C. RS+ VCC RS- Figure 11: AM462 Pin out Table 1: AM462 Pin out analog microelectronics Analog Microelectronics GmbH An der Fahrt 13, D – 55124 Mainz Internet: http://www.analogmicro.de Phone: Fax: Email: +49 (0)6131/91 073 - 0 +49 (0)6131/91 073 – 30 [email protected] December2006 17/20 Rev. 2.4 Industrial V/I Converter and Protector IC AM462 EXAMPLE APPLICATIONS • Application as a voltage-to-current converter IC 6...35V VIN = 0...1, 0...5V ... and other Protection against short circuiting and reverse polarity 0/4...20mA AM462 Figure 12: Application as a current converter IC • Converting a 0.5...4.5V sensor (voltage) signal 6...35V VREF = 5/10V Sensor VOUT = 0.5...4.5V AM462 Protection against short circuiting and reverse polarity 4...20mA Figure 13: Converting a 0.5...4.5V sensor signal • Configuration as a peripheral processor IC [2] VCVR EF = 3.3V µP 6...35V VREF = 5V DAC AM462 Protection against short circuiting and reverse polarity 0/4...20mA Figure 14: Configuration as a peripheral processor IC and supply unit analog microelectronics Analog Microelectronics GmbH An der Fahrt 13, D – 55124 Mainz Internet: http://www.analogmicro.de Phone: Fax: Email: +49 (0)6131/91 073 - 0 +49 (0)6131/91 073 – 30 [email protected] December2006 18/20 Rev. 2.4 Industrial V/I Converter and Protector IC AM462 • Application as an analog output IC and supply unit for sensors VR EF = 5/10V 6...35V VCV REF = 3.3V Sensor µP DAC AM462 Protection against short circuiting and reverse polarity 0/4...20mA Figure 15: Output IC and supply unit in sensor applications • Application as a front-end and back-end IC for microprocessors VCVREF=3.3V 6...35V VREF=5/10V Sensor AM462 Protection against short circuiting and reverse polarity 0/4...20mA ADC DAC µP Figure 16: Application as an analog front end and back end for microprocessors (Frame ASIC concept) analog microelectronics Analog Microelectronics GmbH An der Fahrt 13, D – 55124 Mainz Internet: http://www.analogmicro.de Phone: Fax: Email: +49 (0)6131/91 073 - 0 +49 (0)6131/91 073 – 30 [email protected] December2006 19/20 Rev. 2.4 Industrial V/I Converter and Protector IC AM462 DELIVERY The AM462 V/I converter and protector IC is available as the following packages: • SSOP16 • SO16(n) • Dice on 5" blue foil (on request) PACKAGE DIMENSIONS Please see our website (data sheets: package.pdf). FURTHER READING www.analogmicro.de [1] The Frame ASIC concept: See: [2] The AM462 can be used as an integrated solution to interface a microprocessor to the industrial 4...20mA network. See: Technical Articles: PR1011 and Interfacing the µProcessor with the 4...20mA current loop signal (PLC). See: Application notes AN1014. NOTES Analog Microelectronics reserves the right to make amendments to any dimensions, technical data or other information contained herein without further notice. analog microelectronics Analog Microelectronics GmbH An der Fahrt 13, D – 55124 Mainz Internet: http://www.analogmicro.de Phone: Fax: Email: +49 (0)6131/91 073 - 0 +49 (0)6131/91 073 – 30 [email protected] December2006 20/20 Rev. 2.4