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AD693:  Loop-Powered 4-20 mA Sensor Transmitter

Product Details


The AD693 is a monolithic signal conditioning circuit which accepts low-level inputs from a variety of transducers to control a standard 4-20 mA, two-wire current loop. An on-chip voltage reference and auxiliary amplifier are provided for transducer excitation; up to 3.5 mA 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 mA operation is desired.

Precalibrated 30 mV and 60 mV input spans may be set by simple pin strapping. Other spans from 1 mV to 100 mV may be realized with the addition of external resistors. The auxiliary amplifier may be used in combination with on-chip voltages to provide six precalibrated ranges for 100 (ohm) RTDs. Output span and zero are also determined by pin strapping to obtain the standard ranges: 4-20mA, 12 ± 8 mA and 0-20 mA.

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 cost-effective signal conditioning solution. It is recommended as a replacement for discrete 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 and BENEFITS

  • Instrumentation Amplifier Front End
  • Loop-Powered Operation
  • Independently Adjustable Output Span and Zero
  • Precalibrated Output Spans:
    4-12 mA Unipolar
    0-20 mA Unipolar
    12 ± 8mA Bipolar
  • Precalibrated 20 mV or 60mV Input Spans
  • Precalibrated 100 O 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

Functional Block Diagram for AD693

AD693 Diagram
Functional Block Diagram for AD693

Documentation

Title Content Type File Type
AD693: Loop-Powered 4-20 mA Sensor Transmitter Data Sheet (Rev. A, 10/87) (Rev A, 10/1987) (pdf, 496 kB) Data Sheets PDF
AN-275: Versatile Transmitter Chip Links Strain Gauges and RTDs to Current Loop  (pdf, 948 kB) Application Notes PDF
A Designer's Guide to Instrumentation Amplifiers (3rd Edition) Design Handbooks HTML
Auto-Zero Amplifiers  (doc, 75 kB)
A wide variety of electronic applications, especially those involving very small input signals, require signal paths with very low offset voltage and offset voltage drift over time and temperature.
Technical Articles DOC
High-performance Adder Uses Instrumentation Amplifiers
Make an adder circuit using instrumentation amplifiers to increase input impedance.
(EDN, 9/3/2009)
Technical Articles HTML
Applying Instrumentation Amplifiers Effectively: The Importance of an Input Ground Return  (pdf, 508 kB) Technical Documentation PDF
Leading Inside Advertorials: Applying Instrumentation Amplifiers Effectively–The Importance of an Input Ground Return  (pdf, 121 kB) Overview PDF
RAQs index Rarely Asked Questions HTML
Glossary of EE Terms Glossary HTML

Evaluation Kits & Symbols & Footprints

Symbols and Footprints— Analog Devices offers Symbols & Footprints which are compatible with a large set of today’s CAD systems for broader and easier support.

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Price, packaging, availability

AD693 Model Options
Model Package Pins Temp.
Range
Packing,
Qty
Price*(100-499) Price*1000 pcs RoHS View PCN/ PDN Check Inventory/
Purchase/Sample
AD693AD Status: Production 20 ld Side-Brazed CerDIP 20 Ind Tube, 19 $18.86 $17.02 N  Material Info PCN Purchase
AD693AE Status: Production 20 ld LCC 20 Ind Tube, 54 $23.35 $21.07 N  Material Info PCN Purchase
AD693AQ Status: Production 20 ld CerDIP 20 Ind Tube, 18 $9.58 $8.31 N  Material Info PCN Purchase
Price Table Help

The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.


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