AD7705BR-REEL - 16-Bit Sigma-Delta ADC, 2Ch, SOIC-16 | ADI
MPN: AD7705BR-REEL ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $8.72 | $8.72 |
| 10 | $7.86 | $78.60 |
| 100 | $6.95 | $695.00 |
| 500 | $6.21 | $3,105.00 |
| 1,000 | $5.5 | $5,500.00 |
AD7705BR-REEL Overview
Key features include 16-bit resolution with no missing codes, +/-0.003% nonlinearity, less than 600 nV rms noise, a programmable-gain front end with gains from 1 to 128, on-chip digital filtering, and on-chip calibration that removes zero-scale and full-scale errors as well as temperature drift. Two fully differential input channels are multiplexed into the sigma-delta modulator and digital filter, providing effective resolution up to 16 bits at lower output update rates.
The AD7705BR-REEL operates from a single 2.7 V to 3.3 V supply or a 4.75 V to 5.25 V supply, drawing only 1 mW of power at 3 V - making it attractive for loop-powered industrial transmitters. The sigma-delta architecture inherently shapes quantization noise away from the signal band, delivering excellent normal-mode rejection of 50 Hz/60 Hz mains interference when the output data rate is programmed to match the notch frequency.
Typical applications include weigh scales, pressure transducers, RTD/strain-gauge signal conditioning, industrial process control, temperature measurement, and portable battery-powered instrumentation. The 3-wire serial interface simplifies isolation barrier design in 4-20 mA smart transmitters and lets a low-cost microcontroller configure the part and read conversion data.
When designing with this part, decouple AVDD and DVDD separately with 0.1 uF capacitors placed as close to the pins as possible, and choose the output data rate (and master clock) to align the digital filter notch with 50 Hz or 60 Hz interference. The unbuffered analog input mode requires external input buffers when source impedance exceeds the value listed in the datasheet - see the input buffering section for resistor sizing.
Drop-in alternatives for AD7705BR-REEL — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
AD7705BRZ-REEL
✅ Drop-In📋 Reference alternative (not in catalog)
AD7705BR
✅ Drop-In📋 Reference alternative (not in catalog)
AD7706BR-REEL
✅ Drop-In📋 Reference alternative (not in catalog)
AD7705BNZ
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
AD7705BR-REEL Maximum Ratings & Electrical Characteristics
| Number of Bits | 16 |
| Number of Input Channels | 2 differential |
| ADC Architecture | Sigma-Delta |
| Sampling Rate | Programmable, up to 500 SPS |
| Nonlinearity | 0.003% (+/-) |
| No Missing Codes | 16 bits, guaranteed |
| RMS Noise | <600 nV (at gain = 128, 20 Hz update) |
| Programmable Gain | 1 to 128 |
| Supply Voltage (AVDD/DVDD) | 2.7 V to 3.3 V or 4.75 V to 5.25 V |
| Supply Current (typ.) | 320 uA at 3 V, ~1 mW power consumption |
| Data Interface | SPI, QSPI, MICROWIRE, DSP-compatible 3-wire serial |
| Operating Temperature Range | -40C to +85C (industrial) |
| Package | 16-SOIC (0.295 inch / 7.50 mm body width) |
| Mounting Type | Surface Mount |
| Packaging | Tape & Reel (REEL) |
| On-Chip Calibration | Self-calibration and system calibration (zero/FS) |
| Input Type | Buffered or unbuffered differential (selectable) |
| RoHS Status | Non-RoHS (Pb-bearing BR suffix); see AD7705BRZ-REEL for RoHS-compliant variant |
AD7705BR-REEL Pin Configuration
| Pin 1 | AVDD — Analog supply voltage (2.7V-3.3V or 4.75V-5.25V) |
| Pin 2 | AIN1(+) — Analog input channel 1, positive input |
| Pin 3 | AIN1(-) — Analog input channel 1, negative input |
| Pin 4 | AIN2(+) — Analog input channel 2, positive input |
| Pin 5 | AIN2(-) — Analog input channel 2, negative input |
| Pin 6 | REFIN(+) — Positive reference input |
| Pin 7 | REFIN(-) — Negative reference input |
| Pin 8 | CLKIN — Master clock input (4.9152 MHz typical) |
| Pin 9 | DGND — Digital ground |
| Pin 10 | /CS — Chip select (active low) |
| Pin 11 | SCLK — Serial clock input |
| Pin 12 | DOUT — Serial data output |
| Pin 13 | /DRDY — Data ready output (active low) |
| Pin 14 | MODE — Mode select (clock / calibration mode) |
| Pin 15 | /RESET — Reset input (active low) |
| Pin 16 | DVDD — Digital supply voltage |
Typical Applications
AD7705BR-REEL is suitable for 6 applications: Load Cell / Weigh Scale Signal Conditioning, RTD and Thermocouple Temperature Measurement, Industrial 4-20 mA Smart Transmitter, Portable Battery-Powered Data Loggers, Strain-Gauge and Pressure-Sensor Signal Chain, Process Control Analog Input Modules.
Load Cell / Weigh Scale Signal Conditioning
The AD7705BR-REEL is widely used as the front-end ADC for strain-gauge load cells and weigh scales in industrial scales up to 16-bit precision. Its programmable gain of 1 to 128 lets a single 350-ohm bridge cell be read directly without an external instrumentation amp, while the 20 Hz / 25 Hz output data rate options place the digital filter notches on 50 Hz / 60 Hz mains interference for >80 dB common-mode rejection. Combined with its on-chip self-calibration that removes zero-scale and full-scale errors at every power-up, the part lets a low-cost microcontroller build a NTEP-legal bench scale for under $20 in BOM. The 1 mW power budget is ideal for battery-powered portable scales as well as 4-20 mA loop-powered weigh transmitters.
Recommended
RTD and Thermocouple Temperature Measurement
The AD7705BR-REEL's low rms noise (<600 nV at gain 128) and built-in PGA are well matched to PT100 / PT1000 RTD and J/K-type thermocouple signal chains in process-control transmitters. With gain 128 the part resolves microvolt-level thermocouple Seebeck voltages directly, removing the need for a dedicated chopper-stabilized front end. The sigma-delta digital filter simultaneously rejects 50 Hz / 60 Hz mains pickup on long thermocouple extension wires, eliminating 50/60 Hz beating that otherwise corrupts temperature readings. The 4.75 V to 5.25 V supply range accepts regulated 5 V industrial rails, while the 2.7 V to 3.3 V mode fits battery-powered handheld calibrators with two AA cells.
Recommended
Industrial 4-20 mA Smart Transmitter
The AD7705BR-REEL fits the analog front end of HART or wirelessHART smart transmitters measuring pressure, flow, or level from bridge-type pressure sensors. Its 1 mW power budget is compatible with the 3.5 mA available current budget of an intrinsically safe 4-20 mA loop, after the loop regulator and microcontroller. The 16-bit resolution covers the typical 13-bit normalized transmitter span with headroom for calibration and temperature compensation. SPI-compatible 3-wire interface allows easy opto-isolation between the intrinsically safe side and the digital loop modem, which simplifies IEC 61508 SIL-rated barrier designs in process plants.
Recommended
Portable Battery-Powered Data Loggers
The AD7705BR-REEL's 1 mW typical power consumption at 3 V supply and 2.7 V operation makes it a strong fit for portable battery-powered data loggers measuring slow-moving signals from environmental sensors, soil moisture probes, or structural-strain gauges. In sleep / standby mode the part draws only a few microamps, letting a 2000 mAh lithium-thionyl chloride primary cell run a 2-channel logger for several years on a 1 Hz sample rate. The on-chip calibration eliminates the long-term drift that otherwise mandates periodic field recalibration of remote environmental monitoring stations.
Recommended
Strain-Gauge and Pressure-Sensor Signal Chain
Direct connection of piezoresistive pressure sensors and foil strain gauges to the AD7705BR-REEL's differential inputs eliminates the external instrumentation amplifier usually required in sensor signal chains. The PGA gain of 64 or 128 amplifies the millivolt-level bridge output while keeping the ADC's input within the differential common-mode range, and the on-chip self-calibration removes bridge offset and span error at the user's reference pressure. The result is a 16-bit digital pressure reading directly available over SPI to a microcontroller, suitable for HVAC pressure transmitters and medical blood-pressure cuffs.
Recommended
Process Control Analog Input Modules
The AD7705BR-REEL is widely used on isolated analog-input modules of PLC and DCS systems where 16-bit absolute accuracy and 50/60 Hz rejection are required for thermocouple, RTD, and low-level voltage inputs. Its 16-SOIC small footprint lets 4 to 8 channels fit on a single 1-inch-wide isolated module, while the SPI / MICROWIRE interface cascades easily with digital isolators (e.g., ADuM1411) for 4 kV galvanic isolation. On-chip calibration registers support per-channel span/offset correction in software, removing the need for manual trimpots on every channel of multi-channel acquisition boards.
Recommended
Recommended Products Summary
Engineering reference data for AD7705BR-REEL — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | AD7705BRZ-REEL | AD7706BR-REEL | AD7705BNZ | AD7705BR |
|---|---|---|---|---|---|
| Brand | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices |
| Package | 16-SOIC (7.50 mm) | 16-SOIC (7.50 mm) - same | 16-SOIC (7.50 mm) - same | 16-PDIP - through-hole | 16-SOIC (7.50 mm) - same |
| Resolution | 16-bit | 16-bit | 16-bit | 16-bit | 16-bit |
| Input Channels | 2 differential | 2 differential | 3 pseudo-differential | 2 differential | 2 differential |
| Supply Voltage | 2.7-3.3 V or 4.75-5.25 V | 2.7-3.3 V or 4.75-5.25 V | 2.7-3.3 V or 4.75-5.25 V | 2.7-3.3 V or 4.75-5.25 V | 2.7-3.3 V or 4.75-5.25 V |
| Output Data Rate (max) | 500 SPS | 500 SPS | 500 SPS | 500 SPS | 500 SPS |
| Programmable Gain Range | 1 to 128 | 1 to 128 | 1 to 128 | 1 to 128 | 1 to 128 |
| Typical Power (3V) | ~1 mW | ~1 mW | ~1 mW | ~1 mW | ~1 mW |
| RoHS Compliance | No (Pb-bearing BR) | Yes (lead-free BRZ) | No (Pb-bearing BR) | Yes (lead-free BNZ) | No (Pb-bearing BR) |
Key Differentiators
- Direct replacement option available as lead-free RoHS-compliant BRZ variant (vs AD7705BRZ-REEL)
- Plug-in compatible with 3-channel variant with same SOIC-16 footprint (vs AD7706BR-REEL)
- Lowest power consumption in its ADC resolution class (vs MAX1302)
Design Notes
AD7705BR-REEL operates from a single 2.7V to 3.3V or 4.75V to 5.25V supply and draws ~1mW typical. AVDD (pin 1) and DVDD (pin 16) must be decoupled separately with 0.1uF ceramic capacitors placed as close to each pin as possible, plus a 10uF bulk capacitor on AVDD. For 3V operation a low-noise LDO such as ADP3330 is recommended; for 5V operation, decouple from the digital 5V rail through a ferrite bead to avoid digital noise coupling into the analog front end.
Layout the differential analog input traces (AIN1+/-, AIN2+/-) as symmetric 50-ohm microstrip pairs routed directly above a continuous analog ground plane. Keep digital traces (SCLK, DOUT, /CS, /DRDY) physically separated from analog traces by at least 5mm or surrounded by a ground guard ring. The REFIN+/- traces should be short and decoupled with 0.1uF directly at pins 6/7 because reference noise directly couples into the conversion result.
Estimated: The two input modes (buffered vs unbuffered) trade off input impedance vs input voltage range. Unbuffered mode offers higher absolute input range but requires source impedance below 10kohm to maintain gain accuracy at gain 128. Buffered mode accepts up to 1Mohm source impedance but limits the differential input range to +/-0.6V from COMMON. For bridge transducers choose buffered mode with gain 64 or 128; for higher-voltage inputs use unbuffered mode with an external op amp buffer.
The CLKIN pin (8) accepts a 4.9152 MHz crystal or external CMOS clock; any jitter on this clock translates directly into output-data-rate jitter. Place the crystal within 10mm of the CLKIN pin with a guard ground, and keep the AGND/DGND return currents separated until they meet at a single star-ground point near the analog supply bypass capacitor. Estimated: 1 kohm series termination at SCLK improves signal integrity when the SPI lines exceed 50mm.
Compliance Information
BR suffix indicates lead-bearing (Pb) SOIC package per Analog Devices naming convention. For RoHS-compliant designs use BRZ variant (lead-free, otherwise identical die and SOIC-16 footprint). REACH, AEC-Q100, halogen, and conflict-mineral compliance not explicitly stated in the datasheet excerpts verified - contact Analog Devices for full compliance letter. AEC-Q100 not applicable: industrial / process-control part, not automotive-qualified.
