Datasheet AD693 (Analog Devices)

a
Loop-Powered 4–20 mA Sensor Transmitter AD693 FEATURES FUNCTIONAL BLOCK DIAGRAM Instrumentation Amplifier Front End Loop-Powered Operation Precalibrated 30 mV or 60 mV Input Spans Independently Adjustable Output Span and Zero Precalibrated Output Spans: 4–20 mA Unipolar 0–20 mA Unipolar 12
6
8 mA Bipolar Precalibrated 100
V
RTD Interface 6.2 V Reference with Up to 3.5 mA of Current Available Uncommitted Auxiliary Amp for Extra Flexibility Optional External Pass Transistor to Reduce Self-Heating Errors PRODUCT DESCRIPTION PRODUCT HIGHLIGHTS
The AD693 is a monolithic signal conditioning circuit which 1. The AD693 is a complete monolithic low-level voltage-to- accepts low-level inputs from a variety of transducers to control a current loop signal conditioner. standard 4–20 mA, two-wire current loop. An on-chip voltage 2. Precalibrated output zero and span options include reference and auxiliary amplifier are provided for transducer 4–20 mA, 0–20 mA, and 12 ± 8 mA in two- and three-wire excitation; up to 3.5 mA of excitation current is available when the configurations. device is operated in the loop-powered mode. Alternatively, the device may be locally powered for three-wire applications when 3. Simple resistor programming adds a continuum of ranges 0–20 mA operation is desired. to the basic 30 mV and 60 mV input spans. Precalibrated 30 mV and 60 mV input spans may be set by 4. The common-mode range of the signal amplifier input simple pin strapping. Other spans from 1 mV to 100 mV may extends from ground to near the device’s operating voltage. be realized with the addition of external resistors. The auxiliary 5. Provision for transducer excitation includes a 6.2 V amplifier may be used in combination with on-chip voltages to reference output and an auxiliary amplifier which may be provide six precalibrated ranges for 100 Ω RTDs. Output span configured for voltage or current output and signal and zero are also determined by pin strapping to obtain the amplification. standard ranges: 4–20mA, 12 ± 8 mA and 0–20 mA. 6. The circuit configuration permits simple linearization of Active laser trimming of the AD693’s thin-film resistors result bridge, RTD, and other transducer signals. in high levels of accuracy without the need for additional 7. A monitored output is provided to drive an external pass adjustments and calibration. Total unadjusted error is tested on transistor. This feature off-loads power dissipation to every device to be less than 0.5% of full scale at +25°C, and less extend the temperature range of operation, enhance than 0.75% over the industrial temperature range. Residual reliability, and minimize self-heating errors. nonlinearity is under 0.05%. The AD693 also allows for the use of an external pass transistor to further reduce errors caused by 8. Laser-wafer trimming results in low unadjusted errors and self-heating. affords precalibrated input and output spans. For transmission of low-level signals from RTDs, bridges and 9. Zero and span are independently adjustable and noninteractive pressure transducers, the AD693 offers a cost-effective signal to accommodate transducers or user defined ranges. conditioning solution. It is recommended as a replacement for 10. Six precalibrated temperature ranges are available with a discrete designs in a variety of applications in process control, 100 Ω RTD via pin strapping. factory automation and system monitoring. The AD693 is packaged in a 20-pin ceramic side-brazed DIP, 20-pin Cerdip, and 20-pin LCCC and is specified over the –40°C to +85°C industrial temperature range. REV. A Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
otherwise under any patent or patent rights of Analog Devices.
Tel: 617/329-4700 Fax: 617/326-8703