Loop-Powered 420 mA a Sensor Transmitter AD693 FUNCTIONAL BLOCK DIAGRAM FEATURES Instrumentation Amplifier Front End Loop-Powered Operation Precalibrated 30 mV or 60 mV Input Spans Independently Adjustable Output Span and Zero Precalibrated Output Spans: 420 mA Unipolar 020 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 420 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 420 mA, 020 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 3. Simple resistor programming adds a continuum of ranges device may be locally powered for three-wire applications when to the basic 30 mV and 60 mV input spans. 020 mA operation is desired. 4. The common-mode range of the signal amplifier input Precalibrated 30 mV and 60 mV input spans may be set by extends from ground to near the devices operating voltage. simple pin strapping. Other spans from 1 mV to 100 mV may 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 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: 420mA, 12 8 mA and 020 mA. 6. The circuit configuration permits simple linearization of Active laser trimming of the AD693s 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 +25C, 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 8. Laser-wafer trimming results in low unadjusted errors and of an external pass transistor to further reduce errors caused by affords precalibrated input and output spans. self-heating. 9. Zero and span are independently adjustable and noninteractive For transmission of low-level signals from RTDs, bridges and to accommodate transducers or user defined ranges. pressure transducers, the AD693 offers a cost-effective signal 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 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 40C to +85C 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 One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Tel: 617/329-4700 Fax: 617/326-8703( +258C and V = +24 V. Input Span = 30 mV or 60 mV. Output Span = 420 mA, S AD693SPECIFICATIONS R = 250 V, V = 3.1 V, with external pass transistor unless otherwise noted.) L CM Model AD693AD/AQ/AE Conditions Min Typ Max Units LOOP-POWERED OPERATION 1, 2 TOTAL UNADJUSTED ERROR 0.25 60.5 % Full Scale T to T 0.4 60.75 % Full Scale MIN MAX 3 100 RTD CALIBRATION ERROR (See Figure 17) 0.5 2.0 C 2 LOOP POWERED OPERATION 4 Zero Current Error Zero = 4 mA 25 680 A Zero = 12 mA 40 6120 A 5 Zero = 0 mA +7 +35 +100 A vs. Temp. Zero = 4 mA 0.5 1.5 A/C 6 Power Supply Rejection (RTI) 12 V V 36V 3.0 65.6 V/V OP 0 V V 6.2 V CM 6 Common-Mode Input Range (See Figure 3) 0 +V 4 V V OP Common-Mode Rejection (RTI) 0 V V 6.2 V 10 630 V/V CM 7 Input Bias Current +5 +20 nA T to T +7 +25 nA MIN MAX 7 Input Offset Current V = 0 0.5 63.0 nA SIG Transconductance Nominal 30 mV Input Span 0.5333 A/V 60 mV Input Span 0.2666 A/V Unadjusted Error 0.05 60.2 % vs. Common-Mode 0 V V 6.2 V CM 30 mV Input Span 0.03 0.04 %/V 60 mV Input Span 0.05 0.06 %/V Error vs. Temp. 20 50 ppm/C 8 Nonlinearity 30 mV Input Span 0.01 60.05 % of Span 60 mV Input Span 0.02 60.07 % of Span OPERATIONAL VOLTAGE RANGE 6 Operational Voltage, V +12 +36 V OP Quiescent Current Into Pin 9 +500 +700 A OUTPUT CURRENT LIMIT +21 +25 +32 mA COMPONENTS OF ERROR 9 SIGNAL AMPLIFIER Input Voltage Offset 40 6200 V vs. Temp 1.0 2.5 V/C 6 Power Supply Rejection 12 V V 36 V 3.0 65.6 V/V OP 0 V V 6.2 V CM 9, 10 V/I CONVERTER Zero Current Error Output Span = 420 mA 30 80 A 6 Power Supply Rejection 12 V V 36 V 1.0 3.0 A/V OP Transconductance Nominal 0.2666 A/V Unadjusted Error 0.05 0.2 % 9, 12 6.200 V REFERENCE Output Voltage Tolerance 3 612 mV vs. Temp. 20 50 ppm/C 6 Line Regulation 12 V V 36 V 200 6300 V/V OP 11 Load Regulation 0 mA I 3 mA 0.3 60.75 mV/mA REF 13 Output Current Loop Powered, (Figure 10) +3.0 +3.5 mA 3-Wire Mode, (Figure 15) +5.0 mA REV. 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