AD693 Datasheet | Analog Devices

FEATURES Instrumentation Amplifier Front End Loop-Powered Operation Precalibrated 30 m V or 60 m V Input Spans Independently Adjustable Output Span and Zero Precalibrated Output Spans: 4- 20 m A Unipolar 0- 20 m A Unipolar 12 ؎ 8 m A Bipolar Precalibrated 100 ⍀ RTD Interface 6.2 V Reference with Up to 3.5 m A of Current Available Unmitted Auxiliary Amp for Extra Flexibility Optional External Pass Transistor to Reduce Self-Heating Errors Loop-Powered 4- 20 m A Sensor Transmitter AD693 FUNCTIONAL BLOCK DIAGRAM PRODUCT DESCRIPTION PRODUCT HIGHLIGHTS The AD693 is a monolithic signal conditioning circuit which accepts low-level inputs from a variety of transducers to control a standard 4- 20 m A, two-wire current loop. An on-chip voltage reference and auxiliary amplifier are provided for transducer excitation; up to 3.5 m A of excitation current is available when the device is operated in the loop-powered mode. Alternatively, the device may be locally powered for three-wire applications when 0- 20 m A operation is desired. Precalibrated 30 m V and 60 m V input spans may be set by simple pin strapping. Other spans from 1 m V to 100 m V may be realized with the addition of external resistors. The auxiliary amplifier may be used in bination with on-chip voltages to provide six precalibrated ranges for 100 Ω RTDs. Output span and zero are also determined by pin strapping to obtain the standard ranges: 4- 20m A, 12 ± 8 m A and 0- 20 m A. Active laser trimming of the AD693’s thin-film resistors result in high levels of accuracy without the need for additional adjustments and calibration. Total unadjusted error is tested on every device to be less than 0.5% of full scale at +25°C, and less than 0.75% over the industrial temperature range. Residual nonlinearity is under 0.05%. The AD693 also allows for the use of an external pass transistor to further reduce errors caused by self-heating. For transmission of low-level signals from RTDs, bridges and pressure transducers, the AD693 offers a...