AD694AQ

Overview

The AD694AQ is a monolithic current transmitter manufactured by Analog Devices, designed to drive standard 4–20 mA current loops for process control applications. It accepts high-level voltage inputs and provides precalibrated spans of 0 V to 2 V or 0 V to 10 V via pin strapping. The device operates on a single supply ranging from 4.5 V to 36 V with a quiescent current of 1.5 mA. It features an input buffer amplifier, a precision voltage reference, and an open-loop alarm function. The component is housed in a hermetically sealed 16-pin CERDIP package and is specified for industrial temperatures between -40°C and +85°C.

Feature Summary

• Monolithic integration of voltage-to-current conversion with precalibrated input ranges selectable by pin strapping.
• Input buffer amplifier capable of buffering signals or driving current mode DACs.
• Open-loop alarm output warns of loop failures or output stage noncompliance.
• Optional external pass transistor interface to off-load power dissipation and minimize self-heating errors.

Applications

• Driving valves and actuators in industrial process control systems.
• Transmission of process parameters such as pressure, temperature, or flow.
• Factory automation and system monitoring requiring noise-immune signal transmission.

Procurement Notes

Verify the specific suffix 'AQ' corresponds to the hermetically sealed 16-pin CERDIP package variant when sourcing. Confirm that the supplier provides documentation matching the Rev. C datasheet specifications. Ensure the component meets the -40°C to +85°C industrial temperature range requirements for your application environment before finalizing procurement.

Selection Notes

Select the AD694AQ when a hermetically sealed package is required for harsh environments. Choose this model over plastic variants if long-term reliability in corrosive atmospheres is critical. Ensure the supply voltage supports the selected input span; 10 V reference requires at least 12.5 V supply. Verify that the load impedance allows for the necessary voltage compliance within the 4.5 V to 36 V operating range.

Part Context

The AD694 series serves as a complete solution for 4–20 mA transmitter designs, replacing discrete components. The AQ suffix denotes the ceramic dual in-line package (CERDIP) variant, offering hermetic sealing compared to the plastic DIP (N) or SOIC (R) options. This packaging ensures stability in demanding industrial settings where moisture or chemical exposure might affect standard plastic packages.

Replacement Considerations

Publicly confirmed substitute part numbers are not available in the provided documentation. Designers should verify pin compatibility and electrical specifications against existing discrete designs or alternative transmitters if direct replacement is considered.