AD693AQ

Overview

The AD693AQ is a monolithic signal conditioning circuit designed for two-wire, loop-powered sensor transmitters. It accepts low-level inputs from transducers and controls a standard 4–20 mA current loop. The device features an instrumentation amplifier front end with precalibrated 30 mV or 60 mV input spans. It provides a 6.2 V reference with up to 3.5 mA excitation current. Total unadjusted error is less than 0.5% at +25 °C and 0.75% over the industrial temperature range. It operates on a supply voltage of 12 V to 36 V with a quiescent current of 500 µA. The component is housed in a 20-pin Cerdip package.

Feature Summary

• Monolithic integration of instrumentation amplifier, V/I converter, and voltage reference for complete signal conditioning.
• Loop-powered operation capability with internal transducer excitation providing up to 3.5 mA.
• Laser-trimmed thin-film resistors ensure high accuracy without requiring external calibration adjustments.
• Includes an auxiliary amplifier for additional flexibility in transducer excitation and signal linearization.

Applications

• Two-wire loop-powered sensor transmitters
• RTD (Resistance Temperature Detector) signal conditioning
• Bridge and pressure transducer interface circuits

Procurement Notes

Verify the specific suffix AQ corresponds to the 20-pin Cerdip package configuration required for your assembly process. Confirm that the industrial temperature range of -40°C to +85°C meets your operational environment specifications. Ensure compatibility with existing PCB footprints for ceramic side-brazed DIP packages during procurement planning.

Selection Notes

Select this component when a complete, low-cost solution for converting low-level sensor signals to a 4-20 mA loop is required. It is suitable for replacing discrete designs in process control and factory automation. Consider the external pass transistor option if minimizing self-heating errors is critical for your application's thermal performance requirements.

Part Context

The AD693 series includes variants such as the AD693AD (Ceramic Side-Brazed DIP) and AD693AE (Leadless Ceramic Chip Carrier). The AD693AQ specifically denotes the Cerdip package version. All variants share identical electrical characteristics and functional block diagrams, differing only in physical packaging and mounting style.

Replacement Considerations

No direct public substitute part numbers are confirmed in the provided documentation. Discrete designs previously used may be replaced by this integrated circuit to reduce component count and calibration complexity.

FAQ

How is the input span adjusted?

Input span is adjusted by changing the gain of the Signal Amplifier using pin strapping for 30 mV or 60 mV spans, or by adding external resistors to modify attenuation for other ranges.

What is the purpose of the auxiliary amplifier?

The auxiliary amplifier can be used for transducer excitation, buffering, amplifying signals, or configuring dynamic bridge arrangements such as RTD signal conditioners.

Can the device operate in local-powered mode?

Yes, the AD693 supports local-powered, three-wire applications, which allows for 0–20 mA output operation and improved voltage compliance at the I_IN terminal.