Analog Devices Inc. AD597ARZ

Overview

AD597ARZ from Analog Devices is a precision thermocouple signal conditioner IC for Type K thermocouples, integrating cold-junction compensation, amplification, and linearization to deliver a calibrated 10 mV/°C output. It operates over –40°C to +125°C ambient, supports single- or dual-supply operation (5 V to 36 V total), and achieves ±4°C calibration error at 175°C measurement with ±0.05°C/°C ambient stability. It is used in industrial furnace controllers, process monitoring systems, and laboratory temperature instrumentation.

For engineers reviewing the AD597ARZ datasheet, AD597ARZ pinout, AD597ARZ application, or AD597ARZ equivalent, key selection criteria include its Type K-specific transfer function (V_OUT = 245.46 × (Type K voltage)), absence of integrated alarm functionality (AR package), SOIC-8 packaging, and requirement for external bias return path on thermocouple inputs to prevent input stage saturation.

Technical Context

The AD597ARZ implements a dedicated analog signal chain for Type K thermocouples: it measures thermocouple voltage differentially across Pins 1 and 2, compensates for cold-junction temperature using an on-chip sensor, and applies laser-trimmed gain (245.46 V/V) and offset (–37 µV) to produce a high-level 10 mV/°C output referenced solely to measured temperature. Its input stage accepts differential signals from –10 mV to +50 mV and common-mode voltages from (–V_S – 0.15 V) to (+V_S – 4 V).

Unlike the H-package variant, the AD597ARZ omits the open-thermocouple alarm circuitry - Pin 8 (+ALM) and Pin 9 (–ALM) are not functional and must be tied to Pin 4 or Pin 5 per Figure 1. Its 15 kHz bandwidth and ±5 mA output drive support direct interfacing to A/D converters or panel meters without external buffering.

Key Specifications

Pinout & Package

AD597ARZ is housed in an 8-lead plastic SOIC (SO-8) package with standard JEDEC outline, 1.27 mm pitch, and gull-wing leads. The package is RoHS-compliant and rated for operation from –40°C to +125°C ambient.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar thermocouple signal conditioning applications.

Compared with AD597ARZ, AD8495ACPZ-R7 offers simpler layout but less precise ambient compensation and no analog trim, while MAX31855KASA+ shifts signal processing to the digital domain at the cost of added firmware complexity and loss of direct analog output.

Availability

AD597ARZ is available at Aetrix Electronics and suitable for industrial furnace control, process temperature monitoring, and laboratory thermometer applications requiring stable component supply, long-term obsolescence management, and traceable sourcing.

Supply support for AD597ARZ includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Analog Devices, Inc. is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, founded in 1965 and headquartered in Wilmington, MA.

The AD596/AD597 product line was designed specifically for high-accuracy, low-drift thermocouple signal conditioning in harsh industrial environments, emphasizing analog precision over digital integration.

FAQ

Does AD597ARZ support Type J thermocouples?

No, AD597ARZ is optimized exclusively for Type K thermocouples. Its laser-trimmed gain (245.46 V/V) and offset (–37 µV) match the ANSI Type K voltage vs. temperature curve. Using it with Type J thermocouples introduces significant nonlinearity and calibration error exceeding ±10°C. For Type J applications, the AD596ARZ - a separate part with 180.57 V/V gain and +235 µV offset - must be selected instead.

What is the purpose of Pin 3 on AD597ARZ?

Pin 3 on AD597ARZ is the offset adjust terminal. Injecting or sinking 200 nA of current changes the output voltage by approximately 10 mV (equivalent to 1°C). This allows users to null ambient temperature-induced offset errors during system calibration. The adjustment is implemented via an internal current-controlled voltage source and does not require external op amps or DACs - a simple potentiometer network suffices per Figure 1 in the datasheet.

Can AD597ARZ operate from a single 5 V supply?

Yes, AD597ARZ can operate from a single +5 V supply, but its usable temperature range is restricted. With +5 V supply, the output swings only to +3 V (–V_S + 2.5 V is not applicable in single supply; output minimum is 0 V, maximum is +V_S – 2 V = +3 V). Since output is 10 mV/°C, this limits measurable temperature to 0°C to +300°C. For full –20°C to +350°C coverage, ≥+15 V supply is recommended to ensure output headroom.

Why are Pins 8 and 9 (ALM) not functional on AD597ARZ?

Pins 8 (+ALM) and 9 (–ALM) are alarm outputs available only on the AD597AH (TO-100 metal can) package. The AD597ARZ (SOIC-8) omits this circuitry entirely - these pins have no internal connection and must be externally tied to Pin 4 (–V_S) or Pin 5 (+V_S) per datasheet guidance to prevent undefined behavior. This trade-off reduces cost and package size at the expense of open-thermocouple fault detection capability.

How does AD597ARZ handle thermocouple bias current return paths?

AD597ARZ requires a low-impedance bias return path (≤1 kΩ) from Pins 1 and 2 to ground or reference to supply its 0.1 µA input bias current. Without this path, the input stage saturates, causing erroneous output. If the thermocouple is not remotely grounded, the return path must be provided locally - typically by connecting a resistor from Pin 1 or Pin 2 to ground. The choice determines fault polarity: grounding Pin 1 yields high-voltage saturation on open-circuit (safe default), while grounding Pin 2 yields low-voltage saturation.