AD8495CRMZ

Overview

The AD8495CRMZ is a precision K-type thermocouple amplifier with integrated cold junction compensation, manufactured by Analog Devices Inc. It operates within a supply voltage range of 2.7 V to 36 V and consumes a typical quiescent current of 180 μA. The device provides a linear output transfer function of 5 mV/°C with an initial accuracy of ±1°C at 25°C. It features a 25 kHz bandwidth and settles to 0.1% in 40 μs for a 4 V step. The component is housed in an 8-lead MSOP package and supports an operational temperature range from -40°C to +125°C.

Feature Summary

• Laser-wafer trimmed specifically for K-type (chromel-alumel) thermocouples to ensure accurate signal conditioning.
• Integrated internal temperature sensor performs cold junction compensation to eliminate reference junction errors.
• High impedance differential inputs reject common-mode noise on long thermocouple leads.
• Robust input protection withstands overvoltage conditions up to VS ± 25 V.

Applications

• K-type thermocouple temperature measurement systems
• Setpoint controllers utilizing fixed or remote control
• Standalone Celsius thermometer implementations
• Universal cold junction compensator circuits

Procurement Notes

Verify the specific ordering suffix against official documentation to confirm package type and tape-and-reel specifications. Ensure the selected variant matches the required ambient temperature optimization range for the intended application environment.

Selection Notes

Select this component when precise K-type thermocouple amplification is required without external calibration. Consider the optimized ambient temperature range of 0°C to 50°C for standard laboratory environments. Verify that the single-supply operation meets the system's power constraints and that the 5 mV/°C output aligns with downstream ADC input ranges.

Part Context

This part belongs to the AD849x family of precision thermocouple amplifiers. While sharing similar architecture with J-type variants like the AD8494, it is distinctively calibrated for K-type characteristics. The CRMZ suffix indicates a specific commercial-grade packaging configuration within the broader product line.

Replacement Considerations

Direct functional substitutes include the AD8495ARMZ for alternative packaging or the AD8497 if higher ambient temperature operation (25°C to 100°C) is required. Verify pin compatibility and thermal performance before substitution.

FAQ

How does the AD8495 handle open thermocouple detection?

The device detects open thermocouples because its PNP input stage bias current flows out of the inputs. Connecting the negative input to ground through a 1 MΩ resistor causes the output to rail high if the thermocouple is disconnected.

Can the AD8495 measure temperatures below 0°C on a single supply?

Yes, by applying a positive offset voltage to the REF pin, the device can be configured to measure negative temperatures while operating from a single-ended supply.

What is the recommended method for grounding the thermocouple?

It is recommended to connect the thermocouple to ground through a 100 kΩ to 1 MΩ resistor placed at the negative input on the PCB to prevent ground loops while allowing proper common-mode rejection.