AD7731BRU-REEL7 - 24-Bit Sigma-Delta ADC, 24-TSSOP | Analog Devices
MPN: AD7731BRU-REEL7 ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $16.83 | $16.83 |
| 10 | $15.95 | $159.50 |
| 100 | $14.5 | $1,450.00 |
| 500 | $13.1 | $6,550.00 |
| 1,000 | $11.75 | $11,750.00 |
AD7731BRU-REEL7 Overview
A sigma-delta ADC is a converter architecture that oversamples the input signal at a high modulation rate, shapes quantization noise out of the signal band via a modulator, and decimates a clean low-pass-filtered result at a lower output rate. The AD7731BRU-REEL7 belongs to the converter -> ADC -> sigma-delta ADC -> precision measurement ADC product hierarchy, and is a complete analog front end designed for direct connection to load cells, strain gauges, RTDs, thermocouples, and other low-level transducers in process-control and instrumentation systems.
Key features include a proprietary programmable gain front end accepting input ranges from -1.28 V to +1.28 V with gains from 1 to 128, ±0.0015% integral nonlinearity, ±5 nV/°C offset drift, and ±2 ppm/°C gain drift. The device includes self-calibration and system calibration modes, a configurable three-wire serial interface compatible with microcontrollers and DSPs, and a buffered differential analog input. The 24-pin TSSOP (RU) package and industrial -40°C to +85°C operating range suit it for compact, factory-floor PCB layouts.
The AD7731BRU-REEL7 uses a proprietary switched-capacitor sigma-delta modulator followed by a programmable digital decimation filter, allowing the user to trade resolution against output rate via the filter register. With chop mode enabled, the offset and drift specifications improve further for DC measurement applications. The integrated programmable gain amplifier (PGA) eliminates the need for external signal-conditioning stages when interfacing directly to bridges and low-level sensors.
Typical applications include weigh scales and load-cell signal chains, industrial process-control PLC analog input modules, pressure and strain-gauge transducer readouts, RTD and thermocouple temperature measurement, and laboratory data-acquisition systems. Its low drift and true 24-bit noise-free resolution at reduced output rates make it especially suited to long-term, high-accuracy DC measurements.
When designing with the AD7731BRU-REEL7, pay close attention to grounding and decoupling the four AVDD/AGND pairs and decoupling the reference input with a low-impedance 10 µF/0.1 µF pair. Common pitfalls include using a noisy reference source, omitting input common-mode RC filters, and choosing a CHOP=off configuration when long-term zero-scale drift is critical. Pricing as of 2026-10-12 starts at approximately $16.83 per unit at Heisener with 6,928 pieces in stock.
Drop-in alternatives for AD7731BRU-REEL7 — 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 AD7731BRU-REEL7 (same form factor and footprint) — differing in Package, Programmable Gain, Resolution, Operating Temperature, Calibration.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
AD7731BRUZ-REEL7
✅ Drop-In📋 Reference alternative (not in catalog)
AD7731BRU-REEL
✅ Drop-In📋 Reference alternative (not in catalog)
AD7731BRU
✅ Drop-In📋 Reference alternative (not in catalog)
AD7730BRUZ-REEL7
✅ Drop-In✓ In Stock
$17.4 / Unit
View Datasheet →AD7714YRUZ
✅ Drop-In📋 Reference alternative (not in catalog)
AD7731BRU-REEL7 Maximum Ratings & Electrical Characteristics
| Manufacturer | Analog Devices, Inc. |
| Part Number | AD7731BRU-REEL7 |
| Converter Type | Sigma-Delta ADC |
| Resolution | 24-bit |
| Number of Channels | 3 differential / 5 pseudo-differential |
| Input Voltage Range | -1.28 V to +1.28 V |
| Output Rate (max) | 6.4 kSPS |
| Output Rate Range | 50 Hz to 6.4 kHz (programmable) |
| Peak-to-Peak Resolution | 16 bits p-p |
| Integral Nonlinearity | ±0.0015% |
| Programmable Gain | 1 to 128 (front-end PGA) |
| Offset Drift | < 5 nV/°C |
| Gain Drift | < 2 ppm/°C |
| Operating Temperature | -40 °C to +85 °C |
| Package | 24-TSSOP (RU-24, 4.40 mm width) |
| Mounting Type | Surface Mount |
| Interface | Serial, 3-wire configurable |
| Calibration | Self-calibration + System calibration |
| RoHS Status | Compliant |
AD7731BRU-REEL7 Pin Configuration
| Pin 1 | AIN1 — Analog Input 1 (positive differential input, channel 1) |
| Pin 2 | AIN2 — Analog Input 2 (negative differential input, channel 1) |
| Pin 3 | AIN3 — Analog Input 3 (positive differential input, channel 2) |
| Pin 4 | AIN4 — Analog Input 4 (negative differential input, channel 2) |
| Pin 5 | AIN5 — Analog Input 5 (positive pseudo-differential input, channel 3) |
| Pin 6 | AIN6 — Analog Input 6 (common for pseudo-differential or negative diff input) |
| Pin 7 | REF IN+ — Positive reference input |
| Pin 8 | REF IN- — Negative reference input |
| Pin 9 | AGND — Analog ground |
| Pin 10 | AVDD — Analog +5 V supply |
| Pin 11 | AGND — Analog ground |
| Pin 12 | AVDD — Analog +5 V supply |
| Pin 13 | STANDBY — Standby input (active low) |
| Pin 14 | DGND — Digital ground |
| Pin 15 | DVDD — Digital +5 V supply |
| Pin 16 | MODE/CLK — Mode select / external clock input |
| Pin 17 | DRDY — Data ready output (active low) |
| Pin 18 | CS — Chip select (active low) |
| Pin 19 | SCLK — Serial clock input |
| Pin 20 | DOUT — Serial data output |
| Pin 21 | DIN — Serial data input |
| Pin 22 | SYNC/POR — Synchronization / power-on reset input |
| Pin 23 | AGND — Analog ground |
| Pin 24 | AVDD — Analog +5 V supply |
Typical Applications
AD7731BRU-REEL7 is suitable for 6 applications: Weigh Scales & Load-Cell Readout, Industrial Process Control PLC Analog Inputs, Pressure & Strain-Gauge Transducer Readouts, RTD & Thermocouple Temperature Measurement, Laboratory Data-Acquisition Systems, Medical Diagnostic & Patient Monitoring.
Weigh Scales & Load-Cell Readout
The AD7731BRU-REEL7 is the canonical Analog Devices front end for weigh-scale and load-cell signal chains because its 24-bit sigma-delta architecture, programmable gain front end (PGA gain 1 to 128), and ±5 nV/°C offset drift deliver reliable weight measurements over industrial temperature ranges. With chop mode enabled, the offset drift drops further, supporting long-term zero-scale stability required by OIML and NTEP certified scales. Placed between a 350 Ω bridge load cell and an MCU, the AD7731BRU-REEL7 directly digitizes differential bridge signals of ±10 mV/V full scale without external instrumentation amplifiers, replacing dozens of discrete components.
Recommended
Industrial Process Control PLC Analog Inputs
Factory automation PLC analog input modules use the AD7731BRU-REEL7 to digitize 4-20 mA loop signals, RTD voltages, and bridge outputs in a single compact 24-TSSOP footprint. The programmable digital filter can be set to reject 50 Hz/60 Hz mains interference at exactly the notch frequency the user requires, making the part ideal for IEC 61000-4-30 compliant measurement. With ±0.0015% INL and a true bipolar ±1.28 V input range, the ADC delivers 16-bit p-p resolution at 6.4 kSPS output rate without external signal conditioning.
Recommended
Pressure & Strain-Gauge Transducer Readouts
Pressure transmitters and strain-gauge instrumentation benefit from the AD7731BRU-REEL7 because its high PGA gain (up to 128) accommodates low-output sensors without external amplifiers. The 16-bit p-p resolution at 6.4 kSPS supports pressure transducers with full-scale outputs as small as 1 mV/V while still achieving usable resolution. The on-chip self-calibration and system-calibration routines compensate for sensor offset and gain drift over temperature, simplifying closed-loop factory calibration procedures.
Recommended
RTD & Thermocouple Temperature Measurement
The AD7731BRU-REEL7's low noise (4.5 µV rms at lower output rates) and 5 nV/°C offset drift make it a strong candidate for RTD and thermocouple temperature measurement front ends. With chop mode enabled, the effective drift drops further, supporting Class AA RTD readouts across -40 °C to +85 °C. The 50 Hz minimum output rate mode allows line-frequency notch filtering at exactly 50 Hz or 60 Hz mains, eliminating harmonics from external instrumentation. The serial interface connects directly to most microcontrollers via SPI or QSPI.
Recommended
Laboratory Data-Acquisition Systems
Multi-channel laboratory data-acquisition systems use the AD7731BRU-REEL7 to provide 24-bit precision at up to 6.4 kSPS per channel with channel-to-channel gain matching managed by the on-chip PGA. Its three differential or five pseudo-differential input configurations allow flexible channel allocation for thermocouple, RTD, and bridge transducer inputs simultaneously. The system's self-calibration routine compensates for board-level thermal and aging effects at power-up, achieving 20-bit+ effective resolution at slow output rates for precision benchtop instruments.
Recommended
Medical Diagnostic & Patient Monitoring
Patient monitoring equipment uses the AD7731BRU-REEL7 to digitize low-level biopotential signals (ECG, EEG, EMG) and transducer bridge outputs (blood pressure cuffs, respiration belts) where its high PGA gain eliminates external instrumentation amplifiers. The low offset drift of ±5 nV/°C and gain drift of ±2 ppm/°C maintain measurement accuracy across the -40 °C to +85 °C industrial operating range. The 24-bit resolution provides wide dynamic range for both microvolt-level and millivolt-level signals without range switching, simplifying patient-monitor analog front-end design.
Recommended
Recommended Products Summary
Engineering reference data for AD7731BRU-REEL7 — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | AD7731BRUZ-REEL7 | AD7731BRU-REEL | AD7731BRU | AD7730BRUZ-REEL7 | AD7714YRUZ |
|---|---|---|---|---|---|---|
| Brand | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices |
| Package | 24-TSSOP (RU-24) | 24-TSSOP (RU-24) - same | 24-TSSOP (RU-24) - same | 24-TSSOP (RU-24) - same | 24-TSSOP (RU-24) - same | 24-TSSOP (RU-24) - same |
| Resolution | 24-bit | 24-bit | 24-bit | 24-bit | 24-bit | 24-bit |
| Max Output Rate | 6.4 kSPS | 6.4 kSPS | 6.4 kSPS | 6.4 kSPS | ~1.2 kSPS (slower) | ~10 Hz (much slower) |
| Input Channels | 3 diff / 5 pseudo-diff | 3 diff / 5 pseudo-diff | 3 diff / 5 pseudo-diff | 3 diff / 5 pseudo-diff | 2 diff / 4 pseudo-diff | 3 diff / 5 pseudo-diff |
| Programmable Gain | 1 to 128 | 1 to 128 | 1 to 128 | 1 to 128 | 1 to 128 | 1 to 128 |
| Lead-Free / RoHS | No (lead finish) | Yes (lead-free, RoHS) | No (lead finish) | No (lead finish) | Yes (lead-free, RoHS) | Yes (lead-free, RoHS) |
Key Differentiators
- Highest output rate in 24-bit sigma-delta ADCs with 1 to 128 PGA (vs AD7714YRUZ)
- Lead-free RoHS-compatible drop-in variant available (vs AD7731BRU-REEL (lead version))
- 3 differential / 5 pseudo-differential input channels (vs AD7730BRUZ-REEL7)
Design Notes
Estimated: Decouple each AVDD-AGND pair on the AD7731BRU-REEL7 with a 10 µF tantalum in parallel with a 0.1 µF ceramic placed within 5 mm of the supply pin. According to the manufacturer datasheet, the device draws analog and digital supply currents from four AVDD/AGND pairs; failure to provide local decoupling will couple digital switching noise into the modulator's analog section and degrade SNR. A single shared supply ferrite bead between AVDD and DVDD can further isolate analog and digital domains.
Reference decoupling is critical for the AD7731BRU-REEL7's noise performance. Per the datasheet, place a 10 µF ceramic plus 0.1 µF X7R ceramic directly across the REF IN+ and REF IN- pins, with the ground return star-connected to the ADC analog ground. A noisy reference will couple directly into conversion results; use a low-noise ADR02/ADR03 or equivalent 2.5 V/5 V reference. For weigh-scale applications, a chop-stabilized reference like the ADR440 improves long-term gain stability.
Common pitfalls when designing with the AD7731BRU-REEL7: (1) Forgetting to perform self-calibration after PGA gain changes - calibration constants from one gain do not apply at another gain; (2) Exceeding the input common-mode voltage range when using pseudo-differential mode - AIN6 (common) must be biased to mid-supply; (3) Using digital ground return paths through analog sections, especially under the package; (4) Leaving DRDY un-monitored which can cause missed conversion-data reads. The datasheet's calibration procedure must be followed precisely.
Recommended PCB layout for the AD7731BRU-REEL7 follows the manufacturer evaluation board: place the device on a single ground plane with all analog signals routed on the top layer only, and use a separate digital ground pour under the digital interface signals (SCLK, DOUT, DIN, CS, DRDY) connected to DGND only. Keep analog input traces short and guarded by AGND. The exposed thermal pad on the 24-TSSOP package should be soldered to the AGND plane for thermal dissipation, although this part dissipates only ~25 mW typical so thermal concerns are minor.
Compliance Information
AD7731BRU-REEL7 uses lead (Pb) finish per the -BRU ordering suffix, so it is NOT RoHS-compliant; choose AD7731BRUZ-REEL7 (lead-free, RoHS) for new designs. The die is industrial temperature grade (-40 °C to +85 °C) but is not AEC-Q100 qualified for automotive use.
