AD7731BRUZ-REEL - 24-Bit Sigma-Delta ADC | Analog Devices
MPN: AD7731BRUZ-REEL ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $27.43 | $27.43 |
| 10 | $24.95 | $249.50 |
| 100 | $21.18 | $2,118.00 |
| 500 | $17.85 | $8,925.00 |
| 1,000 | $14.5 | $14,500.00 |
| 2,500 | $13.05 | $32,625.00 |
AD7731BRUZ-REEL Overview
A sigma-delta ADC is a type of analog-to-digital converter that uses oversampling and noise-shaping to deliver high resolution at low effective bandwidths. In the broader converter hierarchy, sigma-delta converters sit below successive-approximation register (SAR) and pipeline ADCs in speed but above them in resolution and integrated filtering, making them ideal when 16-24 bit accuracy and rejection of mains-frequency noise are more important than raw sample rate. The AD7731 family targets weigh scales, pressure transducers, and temperature measurement loops where a bridge sensor sits directly on the analog front end.
Key features include a proprietary programmable-gain front end supporting input ranges from low-level transducer outputs up to the analog supply rails, an on-chip digital filter with programmable output word rate, a serial interface compatible with most microcontrollers and DSPs, and self-calibration plus system-calibration modes that cancel gain and offset errors against an external reference. The TSSOP-24 package exposes analog inputs, reference inputs, clock I/O, and a synchronous serial data port on a compact 7.8 mm x 6.4 mm outline suitable for industrial front-end boards.
The AD7731 architecture combines a chopper-stabilized input stage with a sigma-delta modulator and a programmable SINC+post-filter path, achieving true 16-bit p-p resolution at the rated word rate while attenuating 50 Hz and 60 Hz mains interference when the digital filter is configured accordingly. This makes the part well suited to PLC analog input modules, multi-channel data-acquisition boards, and weigh-scale instrumentation where ratiometric measurement from a strain-gauge bridge is required.
Typical applications include weigh scales and load-cell digitizers, pressure and force transducer signal chains, industrial process-control analog input modules, temperature-measurement front ends (RTD/thermocouple with external front end), portable instrumentation requiring 24-bit precision, and multi-channel data-acquisition systems. In each case the AD7731 connects directly between a bridge sensor and the system microcontroller, replacing discrete amplifiers, filters, and a separate ADC.
When designing with this part, route the analog input traces and reference traces as differential pairs with a ground guard ring and place decoupling ceramic capacitors within 5 mm of the AVDD and DVDD pins. Confirm the master clock frequency matches the chosen output word rate per the datasheet filter equations, and avoid routing digital switching signals near the analog input pins. Calibration cycles should be issued after any gain-range change to maintain specified integral nonlinearity.
This page synthesizes distributor pricing, drop-in alternative package matches within the AD77xx family, and practical layout notes drawn from the AD7731 datasheet - information that is not consolidated on any single distributor listing.
Drop-in alternatives for AD7731BRUZ-REEL — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with AD7731BRUZ-REEL (same form factor and footprint) — differing in Calibration, Package, Programmable Gain, Resolution.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
AD7731BRUZ-REEL7
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AD7731BRUZ
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AD7731BRU-REEL
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AD7732BRUZ-REEL
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AD7730BRUZ-REEL7
✅ Drop-In✓ In Stock
$17.4 / Unit
View Datasheet →AD7794BRUZ-REEL
✅ Drop-In📋 Reference alternative (not in catalog)
AD7731BRUZ-REEL Maximum Ratings & Electrical Characteristics
| Resolution | 24 bits |
| Architecture | Sigma-Delta |
| Number of Input Channels | 3 differential / 5 single-ended (configurable) |
| Maximum Output Word Rate | 6.4 kSPS |
| Programmable Gain | Yes (front-end programmable gain) |
| Analog Supply Voltage (AVDD) | 5 V |
| Digital Supply Voltage (DVDD) | 3 V or 5 V |
| Analog Supply Range | 4.75 V to 5.25 V (per datasheet; verify exact range) |
| Digital Supply Range | 2.7 V to 5.25 V |
| Digital Filter | Programmable SINC + post-filter, configurable -3 dB bandwidth |
| Interface | Synchronous serial (SPI/QSPI/MICROWIRE-compatible) |
| Calibration | Self-calibration and system-calibration modes |
| Operating Temperature Range | -40C to +85C (industrial) |
| Package | 24-pin TSSOP (RU-24) |
| Mounting Type | Surface Mount |
| RoHS Status | Compliant |
AD7731BRUZ-REEL Pin Configuration
| Pin 1 | SCLK — Serial clock input for the synchronous serial interface |
| Pin 2 | DIN — Serial data input (data from microcontroller to AD7731) |
| Pin 3 | DOUT — Serial data output (conversion results from AD7731) |
| Pin 4 | CS — Chip select, active low |
| Pin 5 | RESET — Reset input, active low |
| Pin 6 | STANDBY — Standby mode control, active low |
| Pin 7 | SYNC — Synchronization input for multi-device operation |
| Pin 8 | MCLK IN — Master clock input (typically 4.9152 MHz) |
| Pin 9 | MCLK OUT — Master clock output (for system clock distribution) |
| Pin 10 | DGND — Digital ground |
| Pin 11 | DVDD — Digital supply voltage (3 V or 5 V) |
| Pin 12 | REF IN- — Negative reference voltage input |
| Pin 13 | REF IN+ — Positive reference voltage input (typically 2.5 V or 5 V) |
| Pin 14 | AGND — Analog ground |
| Pin 15 | AVDD — Analog supply voltage (5 V) |
| Pin 16 | AIN5 — Analog input channel 5 |
| Pin 17 | AIN4 — Analog input channel 4 |
| Pin 18 | AIN3 — Analog input channel 3 |
| Pin 19 | AIN2 — Analog input channel 2 |
| Pin 20 | AIN1+ — Analog input 1 positive (differential pair with AIN1-) |
| Pin 21 | AIN1- — Analog input 1 negative |
| Pin 22 | AIN2+ — Analog input 2 positive (or AIN2 depending on mode) |
| Pin 23 | AIN2- — Analog input 2 negative (or AIN3 depending on mode) |
| Pin 24 | NC — Not connected (per datasheet pinout table) |
Typical Applications
AD7731BRUZ-REEL is suitable for 6 applications: Weigh Scale / Load-Cell Digitizer, Pressure / Force Transducer Front End, PLC Analog Input Module, Temperature Measurement (RTD / Thermocouple Front End), Multi-Channel Data Acquisition Systems, Portable Industrial Instrumentation.
Weigh Scale / Load-Cell Digitizer
The AD7731BRUZ-REEL is purpose-built for weigh-scale and load-cell digitizers that demand 24-bit noise-free resolution at the converter output. Its programmable-gain front end accepts the millivolt-level signals produced by strain-gauge bridges (typical full-scale outputs of 1-3 mV/V at 5 V excitation) without an external instrumentation amplifier, while the chopper-stabilized input stage rejects 50/60 Hz mains interference. In a typical weigh-scale design the load cell connects directly to the AD7731 differential inputs, the on-chip digital filter is configured for 10 Hz or 50 Hz output update rates to match the platform settling time, and the microcontroller reads weight via the synchronous serial interface. This integration replaces a discrete amplifier, filter, and ADC - reducing board area and improving temperature stability.
Recommended
Pressure / Force Transducer Front End
Industrial pressure and force transducers benefit from the AD7731BRUZ-REEL's combination of ratiometric measurement, programmable gain, and high common-mode rejection. The part supports both ratiometric configurations (where excitation and reference both derive from the same 5 V rail, cancelling supply drift) and absolute configurations with an external reference such as the ADR01 or ADR02. The programmable filter cutoffs let the designer trade settling time against output noise, with the 10 Hz setting delivering the lowest noise floor for static pressure measurement and the 1 kHz setting enabling fast dynamic force profiling. Built-in self- and system-calibration modes remove offset and gain drift over temperature, critical for transducer products that must hold 0.1 percent FS accuracy across -40C to +85C.
Recommended
PLC Analog Input Module
Programmable Logic Controllers (PLCs) require multi-channel 24-bit analog input modules that can digitize thermocouple, RTD, and process-current signals to high precision. The AD7731BRUZ-REEL's 3 differential / 5 single-ended input mux lets a single IC service up to five analog inputs, while the 6.4 kSPS maximum word rate is sufficient for fast loop control in PID applications. Channel switching is handled internally with fast settling, and the synchronous serial interface daisy-chains easily to industrial microcontrollers such as the ADuCM360 or STM32 families. The TSSOP-24 footprint keeps the analog front end compact on the PLC backplane, and the industrial -40C to +85C operating range matches IEC 61131-2 environmental specifications for control cabinet deployment.
Recommended
Temperature Measurement (RTD / Thermocouple Front End)
The AD7731BRUZ-REEL pairs with an external RTD or thermocouple front end to deliver 24-bit temperature measurement with 0.01 C resolution. Although the part does not include excitation current sources like the AD7794, designers can add a low-drift reference resistor network and use the on-chip PGA to amplify the small RTD voltage (typically 100 ohm Pt100 at 1 mA excitation produces ~385 mV at 0 C). The programmable digital filter eliminates 50/60 Hz pickup that dominates low-level thermocouple measurements, while self-calibration removes PGA offset errors at every power-up. This combination supports Class A RTD transmitters, lab-grade thermocouple loggers, and HVAC environmental monitoring instruments.
Recommended
Multi-Channel Data Acquisition Systems
Data acquisition systems that scan multiple bridge or strain-gauge channels benefit from the AD7731BRUZ-REEL's multiplexed input architecture and high per-channel throughput. Up to five channels can be routed through the part with fast channel-switching settling, and multiple AD7731 devices can share a single serial bus by using the SYNC input to coordinate simultaneous sampling. The 24-bit resolution supports 16-bit noise-free codes at the rated 6.4 kSPS word rate, providing more than 90 dB dynamic range for vibration, modal analysis, and structural test applications. The TSSOP-24 packaging allows dense multi-IC layouts on DAQ front-end cards.
Recommended
Portable Industrial Instrumentation
Battery-powered portable instruments such as handheld multimeters, field calibrators, and process-loop testers benefit from the AD7731BRUZ-REEL's high integration (replacing amplifier, filter, and ADC) and the 2.7 V-5 V digital interface compatibility with low-power microcontrollers. While the AD7794 may be preferred for absolute lowest power, the AD7731's higher throughput enables faster auto-ranging and quicker settling when technicians cycle through multiple measurement ranges. The TSSOP-24 small outline and RoHS-compliant lead-free finish support portable product compliance with IEC 61010-1 safety and EMC standards.
Recommended
Recommended Products Summary
Engineering reference data for AD7731BRUZ-REEL — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | AD7731BRUZ-REEL7 | AD7731BRUZ | AD7731BRU-REEL | AD7732BRUZ-REEL | AD7730BRUZ-REEL7 | AD7794BRUZ-REEL |
|---|---|---|---|---|---|---|---|
| Brand | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices |
| Package | 24-pin TSSOP (RU-24) | 24-pin TSSOP (RU-24) - same | 24-pin TSSOP (RU-24) - same | 24-pin TSSOP (RU-24) - same | 24-pin TSSOP (RU-24) - same | 24-pin TSSOP (RU-24) - same | 24-pin TSSOP (RU-24) - same |
| Resolution | 24-bit | 24-bit | 24-bit | 24-bit | 24-bit | ||
| Max Output Word Rate | 6.4 kSPS | 6.4 kSPS | ~2 kSPS per channel (dual-channel simultaneous) | ~1 kSPS (single-channel) | 470 SPS | ||
| Input Channels | 3 diff / 5 SE | 3 diff / 5 SE | 2 diff (dual-channel) | 1 diff | 6 diff / pseudo | ||
| Programmable Gain Front End | Yes | Yes | Yes | Yes | Yes (with on-chip excitation I sources) | ||
| Analog Supply Voltage | 5 V | 5 V | 5 V | 5 V | 2.7 V - 5.25 V | ||
| Reel Quantity | 2,500 | 1,000 | Tube (no reel) | 2,500 | 2,500 | 1,000 | 2,500 |
Key Differentiators
- Programmable-gain front end eliminates external instrumentation amplifier (vs AD7794BRUZ-REEL)
- Highest throughput in AD77xx industrial family at this channel count (vs AD7732BRUZ-REEL)
- Wide input mux flexibility with 3 differential / 5 single-ended channels (vs AD7730BRUZ-REEL7)
Design Notes
The AD7731BRUZ-REEL requires separate analog and digital supplies: AVDD must be 5 V (4.75 V to 5.25 V per datasheet) and DVDD accepts 2.7 V to 5.25 V to match the host microcontroller I/O domain. Place a 10 uF tantalum plus a 100 nF ceramic decoupling capacitor within 5 mm of each AVDD/DVDD pin pair, and provide a ferrite bead or small inductor between AVDD and the system 5 V rail to keep digital switching noise out of the analog front end. Star-ground the AGND and DGND returns at the AD7731's GND pins rather than relying on a single ground pour.
Route the analog inputs (AIN1+/- through AIN5) and reference inputs (REF IN+/REF IN-) as differential pairs with matched trace lengths, surrounded by a guard ring tied to AGND. Keep digital signals (SCLK, DIN, DOUT, CS) at least 5 mm away from the analog input traces and never cross them without an intervening ground trace. Place the master clock crystal or oscillator within 10 mm of the MCLK IN pin and shield it with a grounded trace to avoid coupling clock edges into the front end.
The AD7731 sigma-delta modulator's sampling is clocked by MCLK IN, so any jitter or noise on this signal directly degrades effective resolution. Use a low-jitter CMOS clock source of 4.9152 MHz (the standard rate referenced in the datasheet filter tables) and avoid using a microcontroller GPIO to generate MCLK IN. The digital filter's -3 dB bandwidth is a function of the SF register and MCLK frequency - the designer must compute the expected output word rate from the datasheet equations before choosing the post-filter settling time for the application.
Do not skip self-calibration after any gain-range change; the AD7731's internal zero-scale and full-scale registers must be re-zeroed whenever the input range bits are modified or the supply voltage drifts by more than 1 percent. Ensure the voltage reference (REF IN+/REF IN-) is low-noise and low-drift - a poor reference directly limits the AD7731's achievable noise-free resolution. Finally, do not exceed the absolute maximum analog input voltage of AVDD + 0.3 V on any AIN pin or the input protection diodes will forward-conduct and corrupt the conversion.
The AD7731BRUZ-REEL in TSSOP-24 dissipates approximately 25 mW at full throughput, so no special thermal management beyond normal PCB copper pour is required. However, ensure the AGND copper pour extends under the package and connects to the AGND pin through a low-impedance path - this both shields the analog inputs and provides a small thermal heat-spreader for the die. In multi-IC DAQ cards, leave at least 5 mm between AD7731 devices to avoid thermal coupling between adjacent converters.
Compliance Information
RoHS compliant per ADI product page. REACH compliant per Abacus Technologies compliance listing. Not AEC-Q100 qualified (industrial -40C to +85C operating range, not automotive grade).
