AD7731BRU

Overview

The AD7731BRU is a complete analog front-end for process control applications, featuring a 24-bit sigma-delta ADC architecture. It operates from a single +5 V supply and includes a programmable gain front end with three buffered differential inputs configurable as five pseudo-differential inputs. The device supports seven unipolar ranges (0 to ±20 mV to ±1.28 V) and seven bipolar ranges. It achieves 16 bits of peak-to-peak resolution at an 800 Hz output rate, with programmable rates up to 6.4 kHz. Key specifications include an offset drift of less than 5 nV/°C, gain drift of less than 2 ppm/°C, and integral nonlinearity of 15 ppm of FSR. It utilizes a serial interface compatible with microcontrollers and DSPs.

Feature Summary

• Features a proprietary programmable gain front end accepting low-level signals directly from transducers.
• Includes self-calibration and system calibration options to minimize offset and gain errors.
• Integrates a two-stage digital filter allowing adjustment of cutoff frequency, output rate, and settling time.
• Provides FASTStep mode for rapid channel sequencing with 1 ms settling time.

Applications

• Process Control
• PLCs/DCS
• Industrial Instrumentation

Procurement Notes

Verify the specific package type required for your design, as the AD7731 series is available in multiple configurations including TSSOP, SOIC, and PDIP. Confirm that the B version meets your operating temperature range requirements of -40°C to +85°C. Ensure compatibility with your system's voltage levels, specifically the AVDD and DVDD supplies. Check for RoHS compliance if necessary, noting that suffix Z indicates compliance. Validate pinout alignment with your PCB layout before finalizing procurement.

Selection Notes

Select the AD7731BRU when a 24-lead TSSOP package is required for space-constrained designs. Consider the AD7731BN or AD7731BR variants if through-hole or surface-mount SOIC packages are preferred instead. Evaluate the need for chopped mode operation to further reduce drift errors if extreme precision is required. Ensure the external reference voltage matches the HIREF bit configuration for optimal performance. Verify that the master clock frequency aligns with the specified 1 MHz to 5 MHz range for accurate data conversion.

Part Context

The AD7731 is part of Analog Devices' high-performance data converter portfolio, designed specifically for industrial process control environments. It integrates a sigma-delta modulator, programmable gain amplifier, and digital filter into a single chip. This integration reduces the component count and board space required for high-precision measurement systems. The device is widely used in applications requiring robust signal conditioning and high-resolution analog-to-digital conversion.

Replacement Considerations

Direct replacements within the same family include AD7731BRZ (RoHS compliant TSSOP), AD7731BR (SOIC), and AD7731BN (PDIP). These parts share identical electrical characteristics and pinouts. Ensure that any substitute maintains the same package dimensions and thermal properties. Verify that the replacement part meets the same temperature and voltage specifications.