PRODUCT DESCRIPTION:

The AD693 is a monolithic signal conditioning circuit whichaccepts low-level inputs from a variety of transducers to control astandard 4–20 mA, two-wire current loop. An on-chip voltagereference and auxiliary amplifier are provided for transducerexcitation; up to 3.5 mA of excitation current is available when thedevice is operated in the loop-powered mode. Alternatively, thedevice may be locally powered for three-wire applications when0–20 mA operation is desired.Precalibrated 30 mV and 60 mV input spans may be set bysimple pin strapping. Other spans from 1 mV to 100 mV maybe realized with the addition of external resistors. The auxiliaryamplifier may be used in combination with on-chip voltages toprovide six precalibrated ranges for 100 Ω RTDs. Output spanand zero are also determined by pin strapping to obtain thestandard ranges: 4–20mA, 12 ± 8 mA and 0–20 mA.Active laser trimming of the AD693’s thin-film resistors resultin high levels of accuracy without the need for additionaladjustments and calibration. Total unadjusted error is tested onevery device to be less than 0.5% of full scale at +25°C, and lessthan 0.75% over the industrial temperature range. Residualnonlinearity is under 0.05%. The AD693 also allows for the useof an external pass transistor to further reduce errors caused byself-heating.For transmission of low-level signals from RTDs, bridges andpressure transducers, the AD693 offers a cost-effective signalconditioning solution. It is recommended as a replacement fordiscrete designs in a variety of applications in process control,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.

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: 

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