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AD210 датащи(PDF) 8 Page - Analog Devices |
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AD210 датащи(HTML) 8 Page - Analog Devices |
8 / 9 page AD210 REV. A –7– lent current VOUT/2 kΩ. This resistor directly affects the output gain temperature coefficient, and must be of suitable stability for the application. The external low power op amp, powered by +VOSS and –VOSS, maintains its summing junction at output common. All the current flowing through the 2 k Ω resistor flows through the output Darlington pass devices. A Darlington con- figuration is used to minimize loss of output current to the base. IOUT 15 +VOSS +VISS –VISS +15V 2 –VOSS 14 1 LF441 +VOSS –VOSS 3 VSIG 0-10V 19 18 AD210 2k Ω 2N3906 (2) 16 17 4 FDH333 IOUT RETURN 30 29 Figure 18. Self-Powered Isolated Current Source The low leakage diode is used to protect the base-emitter junc- tion against reverse bias voltages. Using –VOSS as a current return allows more than 10 V of compliance. Offset and gain control may be done at the input of the AD210 or by varying the 2 k Ω resistor and summing a small correction current directly into the summing node. A nominal range of 1 mA– 5 mA is recommended since the current output cannot reach zero due to reverse bias and leakage currents. If the AD210 is powered from the input potential, this circuit provides a fully isolated, wide bandwidth current output. This configuration is limited to 5 mA output current. Isolated V-to-I Converter Illustrated in Figure 19, the AD210 is used to convert a 0 V to +10 V input signal to an isolated 4–20 mA output current. The AD210 isolates the 0 V to +10 V input signal and provides a proportional voltage at the isolator’s output. The output circuit converts the input voltage to a 4–20 mA output current, which in turn is applied to the loop load RLOAD. RLOAD 15 +VOSS +VISS –VISS +15V 2 –VOSS 14 1 +VS –VS 3 VSIG 19 18 AD210 500 Ω 2N2907 16 17 4 CURRENT LOOP 143 Ω 3.0k ADJUST TO 4mA WITH 0V IN +28V CURRENT LOOP 2N2219 576 Ω 1N4149 SPAN ADJ 100 Ω 30 29 AD308 Figure 19. Isolated Voltage-to-Current Loop Converter Isolated Thermocouple Amplifier The AD210 application shown in Figure 20 provides amplifica- tion, isolation and cold-junction compensation for a standard J type thermocouple. The AD590 temperature sensor accurately monitors the input terminal (cold-junction). Ambient tempera- ture changes from 0 °C to +40°C sensed by the AD590, are can- celled out at the cold junction. Total circuit gain equals 183; 100 and 1.83, from A1 and the AD210 respectively. Calibration is performed by replacing the thermocouple junction with plain thermocouple wire and a millivolt source set at 0.0000 V (0 °C) and adjusting RO for EOUT equal to 0.000 V. Set the millivolt source to +0.02185 V (400 °C) and adjust R G for VOUT equal to +4.000 V. This application circuit will produce a nonlinearized output of about +10 mV/ °C for a 0°C to +400°C range. +VOSS +VISS –VISS +15V 2 –VOSS 3 18 AD210 16 17 4 13.7k 30 29 10k RG 5k A1 19 –VISS 10k 220pF 100k THERMAL CONTACT 52.3 Ω COLD JUNCTION –VISS +VISS 1k -20k- "J" 15 14 1000pF 1 VOUT AD590 AD OP-07 R G Figure 20. Isolated Thermocouple Amplifier Precision Floating Programmable Reference The AD210, when combined with a digital-to-analog converter, can be used to create a fully floating voltage output. Figure 21 shows one possible implementation. The digital inputs of the AD7541 are TTL or CMOS compat- ible. Both the AD7541 and AD581 voltage reference are pow- ered by the isolated power supply + VISS. ICOM should be tied to input digital common to provide a digital ground reference for the inputs. The AD7541 is a current output DAC and, as such, requires an external output amplifier. The uncommitted input amplifier internal to the AD210 may be used for this purpose. For best results, its input offset voltage must be trimmed as shown. The output voltage of the AD210 will go from 0 V to –10 V for digital inputs of 0 and full scale, respectively. However, since the output port is truly isolated, VOUT and OCOM may be freely interchanged to get 0 V to +10 V. This circuit provides a precision 0 V–10 V programmable refer- ence with a ±3500 V common-mode range. +VOSS +VISS –VISS +15V –VOSS AD210 200 Ω 1k Ω +VISS VOUT 0 - –10V 100k Ω 50k Ω 17 1 3 2 18 16 12-BIT DIGITAL INPUT 2k Ω GAIN HP5082-2811 OR EQUIVALENT +VISS AD581 OFFSET 17 15 4 1 3 2 18 16 4 15 19 14 30 29 Figure 21. Precision Floating Programmable Reference |
Аналогичный номер детали - AD210_16 |
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Аналогичное описание - AD210_16 |
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