Analog Devices Inc. AD7731BRZ

Overview

AD7731BRZ from Analog Devices is a 24-bit sigma-delta analog-to-digital converter optimized for high-precision industrial process control front ends. It integrates a programmable gain amplifier (PGA), buffered differential inputs, a 22-tap FIR + SINC³ digital filter, FASTStep™ mode for rapid channel settling, and supports 7 unipolar/bipolar input ranges down to ±20 mV. It operates from a single +5 V AVDD supply with <2 ppm/°C gain drift and achieves 16-bit peak-to-peak resolution at 800 Hz output rate.

For engineers reviewing the AD7731BRZ datasheet, AD7731BRZ pinout, AD7731BRZ application, or AD7731BRZ equivalent, this device serves as a complete transducer interface IC requiring no external signal conditioning for low-level sensor signals in PLCs, DCS, and industrial instrumentation-where offset drift (<5 nV/°C), 50/60 Hz rejection (>120 dB), and self-calibration are critical selection criteria.

Technical Context

The AD7731BRZ implements a two-stage digital filter architecture: a configurable SINC³ modulator output stage followed by either a fixed 22-tap FIR filter (default) or FASTStep™ adaptive filter for step-input transient response. Its on-chip PGA provides seven selectable gain settings enabling direct connection of millivolt-level transducers without external amplification.

It features three fully differential analog input channels (configurable as five pseudo-differential pairs), a differential reference input supporting +2.5 V or +5 V references, and dual-purpose pins AIN3/D1 and AIN4/D0 that function as either analog inputs or programmable digital outputs under register control-enabling embedded system I/O expansion without additional GPIO.

Key Specifications

Pinout & Package

AD7731BRZ is housed in a 24-lead SOIC_W (RW-24) package, RoHS-compliant, with 1.27 mm pitch and standard JEDEC MS-013 footprint. Thermal impedance θ_JA = 75°C/W enables operation up to +85°C ambient without forced airflow.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-resolution sigma-delta ADC applications.

Compared with AD7731BRZ, AD7190BRUZ offers superior noise performance but lacks FASTStep™ and I/O flexibility, while ADS1258IPWR delivers higher speed and channel density at the cost of calibration overhead and missing integrated diagnostics like burnout detection.

Availability

AD7731BRZ is available at Aetrix Electronics and suitable for industrial instrumentation, PLC analog input modules, and high-accuracy weigh scales requiring stable component supply with guaranteed long-term availability and RoHS compliance.

Supply support for AD7731BRZ 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 is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, founded in 1965 and headquartered in Wilmington, MA.

The AD7731BRZ belongs to Analog Devices' precision sigma-delta ADC product line, designed specifically for industrial process control applications demanding low drift, high noise immunity, and integrated transducer interface functionality.

FAQ

What is the maximum output data rate supported by the AD7731BRZ?

The AD7731BRZ supports programmable output rates up to 6.4 kHz in SKIP mode, where only the SINC³ filter is active. In normal mode with both SINC³ and 22-tap FIR filtering enabled, the maximum rate is 800 Hz-delivering 16-bit peak-to-peak resolution. The device's FASTStep™ mode maintains 13-bit resolution during 1 ms channel switching, making it ideal for multiplexed sensor arrays. AD7731BRZ configuration registers allow real-time rate adjustment without hardware changes.

Does the AD7731BRZ require an external reference voltage?

No, the AD7731BRZ accepts an external differential reference but does not require one-it operates ratiometrically using its own internal reference derived from AVDD when configured appropriately. The REF IN(+) and REF IN(–) inputs support nominal +2.5 V or +5 V references selected via the HIREF bit; however, the part can also use AVDD as reference if the HIREF bit is cleared and external reference pins are tied accordingly. AD7731BRZ's reference detect circuitry flags open/short conditions to prevent erroneous conversions.

How does the FASTStep™ mode improve multi-channel performance in the AD7731BRZ?

FASTStep™ mode dynamically replaces the default 22-tap FIR filter with a faster-converging adaptive filter upon detecting a step change at the input-reducing settling time from typical FIR settling (tens of milliseconds) to 1 ms while preserving ≥13-bit peak-to-peak resolution. This enables rapid scanning across up to six analog inputs (AIN1–AIN6) in process control systems without sacrificing accuracy. AD7731BRZ automatically engages FASTStep™ when input transitions exceed programmable thresholds, then reverts to FIR filtering for steady-state precision.

Can the AD7731BRZ perform self-calibration without external equipment?

Yes, the AD7731BRZ includes on-chip self-calibration for both offset and full-scale errors using internal precision voltage sources. Internal zero-scale calibration reduces offset to ~3 µV typical; internal full-scale calibration reduces gain error to <100 ppm on most ranges. System calibration-using user-applied known voltages-is also supported and drives errors to the noise floor. All calibrations are initiated via serial interface commands; no external DACs, references, or test fixtures are needed. AD7731BRZ stores calibration coefficients in on-chip registers for persistent correction.

What packaging and compliance status applies to the AD7731BRZ?

The AD7731BRZ is supplied in a 24-lead SOIC_W (RW-24) package with RoHS-compliant lead finish and halogen-free molding compound. It meets JEDEC standards for moisture sensitivity level (MSL) 3 and is qualified for industrial temperature range (–40°C to +85°C). The "Z" suffix explicitly denotes RoHS compliance per Analog Devices' ordering guide; the "-REEL7" variant indicates 7-inch tape-and-reel packaging for automated assembly. AD7731BRZ shares footprint compatibility with AD7731BR and AD7731BRU variants, enabling design reuse across package options.