AD594CQ

Overview

The AD594CQ is a monolithic thermocouple amplifier with built-in cold junction compensation, designed for Type J thermocouples. It provides a low-impedance voltage output of 10 mV/°C and features laser wafer trimming to ±1°C calibration accuracy at +25°C. The device operates on a wide power supply range from +5 V to +30 V (or dual supplies spanning 30 V) with typical quiescent current under 160 µA. It includes a thermocouple failure alarm with TTL drive capability and supports setpoint control or standalone Celsius thermometer operation.

Feature Summary

• Integrated instrumentation amplifier and ice point reference providing direct temperature-proportional output
• Laser-wafer trimmed for Type J thermocouple characteristics with high calibration accuracy
• Built-in thermocouple open-circuit detection with flexible alarm output format
• Flexible pin-strapping allows configuration as linear amplifier, setpoint controller, or Celsius transducer

Applications

• Industrial temperature measurement systems requiring Type J thermocouple interfacing
• Setpoint temperature controllers using fixed or remote setpoint voltages
• Standalone Celsius temperature transducers in low-power environments
• Applications requiring thermocouple lead failure detection and alarm signaling

Procurement Notes

Verify the specific C-grade performance specifications against system requirements, particularly the ±1°C calibration accuracy at +25°C. Confirm that the operating ambient temperature range aligns with the specified limits. Ensure the package type matches the intended PCB layout, as this model utilizes a hermetically sealed ceramic DIP or cerdip housing. Cross-reference the datasheet revision to confirm compatibility with existing design documentation.

Selection Notes

Select the AD594CQ when precise conditioning of Type J thermocouples is required without external compensation components. This part is suitable for designs needing integrated cold junction correction and a linearized 10 mV/°C output. Consider the C-grade accuracy if tighter thermal tolerance is necessary compared to the A-grade variant. Evaluate the single-supply or dual-supply configuration needs based on whether negative temperature measurement is required.

Part Context

The AD594CQ belongs to the AD594/AD595 family of monolithic thermocouple amplifiers. While the AD595 is calibrated for Type K inputs, the AD594 is specifically optimized for Type J (iron-constantan) thermocouples. Both share identical functional architectures, including internal ice point compensation and alarm outputs. The 'C' suffix denotes the commercial grade with higher calibration precision compared to the 'A' grade.

Replacement Considerations

The AD594CD serves as the standard alternative within the same product line, offering identical electrical characteristics but potentially in a different package option such as the TO-116 D-14 side-brazed DIP. Verify package dimensions and pinout compatibility before substitution.