AD7708BR-REEL - 16-Bit 8/10-Ch Sigma-Delta ADC | Analog Devices
MPN: AD7708BR-REEL ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $9.86 | $9.86 |
| 10 | $8.92 | $89.20 |
| 100 | $7.45 | $745.00 |
| 500 | $6.62 | $3,310.00 |
| 1,000 | $6.19 | $6,190.00 |
AD7708BR-REEL Overview
A sigma-delta ADC is a type of oversampling converter that trades speed for resolution and in-band noise: it samples the analog input at a much higher rate than Nyquist, shapes quantization noise out of the baseband using an internal modulator, then low-pass filters and decimates the resulting bitstream to deliver high effective number of bits (ENOB). Within the broader product hierarchy the AD7708 belongs to the precision ADC family, sitting between general-purpose successive-approximation (SAR) ADCs (lower resolution / higher speed) and 24-bit sigma-delta converters such as the pin-compatible AD7718 (higher resolution, otherwise identical). It also relates to a wider category of low-power precision data-acquisition ICs used in industrial, instrumentation and sensor-interface designs.
Key features include factory-calibrated offset and gain (no user trims required), 8 single-ended or 4 fully-differential input channels (software-configurable as 8/10 pseudo-differential inputs), programmable gain from 1 to 128, an SPI/QSPI/MICROWIRE/DSP-compatible serial interface, and on-chip calibration registers. The output update rate is user-programmable, and a low-side chop buffer plus chop-stabilized input front-end minimize input offset drift across temperature.
The sigma-delta modulator architecture provides inherent 16-bit noise-free resolution at low update rates while delivering excellent normal-mode rejection at the chosen notch frequency, which is critical when digitizing signals in electrically noisy environments. The integrated PGA allows small sensor signals (e.g., strain-gauge bridges or thermocouples) to be amplified up to 128x before digitization, eliminating external instrumentation amplifiers in many designs.
Typical applications include industrial process-control analog input modules, multi-channel temperature measurement (with thermocouple or RTD front ends), weigh scales, portable instrumentation, smart sensor transmitters, and programmable logic controller (PLC) analog front ends. The wide input-voltage range and high common-mode rejection also suit battery-management monitoring and 4-20 mA loop digitization.
When designing with the AD7708BR-REEL, ensure that the analog supply (AVDD) is well decoupled with a 10 uF tantalum in parallel with a 0.1 uF ceramic close to the pins, and that the digital supply (DVDD) is similarly bypassed. The reference input REF IN(+) / REF IN(–) should be driven from a low-impedance, low-noise source such as the ADR01 or AD780; reference noise directly translates to output noise. A continuous input current exceeding the absolute maximum will latch the input ESD structure, so a 100 ohm series resistor or external clamping is recommended in harsh environments.
This page synthesizes distributor pricing, real drop-in pin-compatible alternatives, and practical design notes not found in the manufacturer datasheet alone.
Drop-in alternatives for AD7708BR-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 AD7708BR-REEL (same form factor and footprint) — differing in Number of Input Channels, Operating Temperature Range, Package, Packaging.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
AD7708BR-REEL7
✅ Drop-In📋 Reference alternative (not in catalog)
AD7708BRZ-REEL
✅ Drop-In📋 Reference alternative (not in catalog)
AD7718BR-REEL
✅ Drop-In📋 Reference alternative (not in catalog)
AD7718BRZ-REEL
✅ Drop-In📋 Reference alternative (not in catalog)
AD7708BRUZ-REEL7
✅ Drop-In📋 Reference alternative (not in catalog)
AD7708BRU-REEL
✅ Drop-In✓ In Stock
$6.19 / Unit
View Datasheet →AD7708BR-REEL Maximum Ratings & Electrical Characteristics
| Resolution | 16 bits |
| Number of Input Channels | 8 single-ended / 4 differential (software-configurable as 8/10 pseudo-differential) |
| ADC Architecture | Sigma-Delta |
| Package | 28-SOIC (0.295 inch / 7.50 mm wide body) |
| Supply Voltage | 2.7 V to 5.25 V |
| Programmable Gain | 1 to 128 |
| Data Interface | DSP, MICROWIRE, QSPI, Serial, SPI |
| Input Type | Pseudo-Differential / Differential (factory-calibrated) |
| Calibration | Factory-calibrated (self-calibration supported) |
| Operating Temperature Range | -40 C to +85 C (industrial) |
| Mounting Type | Surface Mount |
| Packaging | Tape & Reel (13 inch, REEL) |
| Pin/Package Count | 28 pins |
AD7708BR-REEL Pin Configuration
| Pin 1 | SCLK — Serial clock input for SPI/QSPI/MICROWIRE/DSP-compatible interface |
| Pin 2 | DOUT — Serial data output from the AD7708 to the host |
| Pin 3 | DIN — Serial data input from the host to the AD7708 |
| Pin 4 | CS — Chip-select input (active low) for the serial interface |
| Pin 5 | SYNC/RESET — Synchronization or hardware reset input |
| Pin 6 | MCLK IN — Master clock input (external crystal or clock source) |
| Pin 7 | MCLK OUT — Master clock output (for external crystal or buffered clock) |
| Pin 8 | DGND — Digital ground return for DVDD |
| Pin 9 | DVDD — Digital supply input (2.7 V to 5.25 V) |
| Pin 10 | REF IN(-) — Negative reference input |
| Pin 11 | REF IN(+) — Positive reference input |
| Pin 12 | AIN1 — Analog input channel 1 |
| Pin 13 | AIN2 — Analog input channel 2 |
| Pin 14 | AIN3 — Analog input channel 3 |
| Pin 15 | AIN4 — Analog input channel 4 |
| Pin 16 | AIN5 — Analog input channel 5 |
| Pin 17 | AIN6 — Analog input channel 6 |
| Pin 18 | AIN7 — Analog input channel 7 |
| Pin 19 | AIN8 — Analog input channel 8 |
| Pin 20 | NC — Not connected (per datasheet) |
| Pin 21 | NC — Not connected (per datasheet) |
| Pin 22 | AGND — Analog ground return for AVDD |
| Pin 23 | AVDD — Analog supply input (2.7 V to 5.25 V) |
| Pin 24 | STBY — Standby mode control (active low, optional use) |
| Pin 25 | NC — Not connected (per datasheet) |
| Pin 26 | NC — Not connected (per datasheet) |
| Pin 27 | NC — Not connected (per datasheet) |
| Pin 28 | NC — Not connected (per datasheet) |
Typical Applications
AD7708BR-REEL is suitable for 6 applications: Industrial Process-Control Analog Input Module, Multi-Channel Temperature Measurement (RTD / Thermocouple), Weigh Scale / Load-Cell Digitization, Smart Sensor Transmitter (4-20 mA Loop-Powered), Programmable Logic Controller (PLC) Analog Front End, Battery Cell Monitoring and Management (BMS).
Industrial Process-Control Analog Input Module
The AD7708BR-REEL is well suited for multi-channel industrial process-control analog input modules because it integrates an 8/10-channel input multiplexer and programmable gain of 1 to 128, allowing up to ten 4-20 mA loop signals (after shunt conversion) to be digitized with a single chip. According to the manufacturer datasheet, factory-calibrated offset and gain, plus an SPI-compatible digital interface, eliminate external trims and simplify the host microcontroller interface. The 2.7 V to 5.25 V supply range and industrial -40 C to +85 C temperature rating support standard 24 V industrial backplanes regulated down to 5 V or 3.3 V on the module.
Recommended
Multi-Channel Temperature Measurement (RTD / Thermocouple)
The AD7708BR-REEL fits multi-channel temperature measurement front ends because the integrated programmable gain amplifier (gain 1 to 128) amplifies small thermocouple or RTD signals to full-scale before digitization, removing external instrumentation amplifiers. The 16-bit noise-free resolution at low output rates (5 Hz to 60 Hz notch) provides the dynamic range needed for type K, J or T thermocouples (tens of microvolts per degree C). With 8 single-ended or 4 differential inputs, one AD7708 can digitize multiple thermocouple junctions or RTD bridges in a panel meter, oven controller, or thermal data logger.
Recommended
Weigh Scale / Load-Cell Digitization
The AD7708BR-REEL supports weigh-scale and load-cell designs because the integrated programmable gain (1 to 128) lets the small full-scale output of a 2 mV/V load cell be amplified to within the ADC's full-scale input range without external INAs. Factory calibration eliminates the long manual trim step normally required for weigh scales. The SPI-compatible digital interface and software-programmable output update rate allow easy adjustment of the digital filter notch to reject mains-induced 50 Hz / 60 Hz interference in scale installations.
Recommended
Smart Sensor Transmitter (4-20 mA Loop-Powered)
The AD7708BR-REEL is appropriate for smart sensor transmitters because it operates from a 2.7 V to 5.25 V supply and consumes only microamperes of quiescent current, leaving the majority of the 4 mA loop-current budget for sensor excitation and the loop-side microcontroller. The 16-bit resolution over an 8-channel input mux allows multiple sensor inputs (temperature, pressure, flow) to be combined in a single transmitter. Its industrial -40 C to +85 C rating supports outdoor and process-plant installations.
Recommended
Programmable Logic Controller (PLC) Analog Front End
The AD7708BR-REEL is a strong fit for PLC analog input cards because a single chip can serve 8/10 channels, dramatically reducing part count on high-density I/O modules. The factory-calibrated PGA and low input-referred noise simplify analog front-end design and free up board area for digital isolation barriers. The SPI/QSPI/MICROWIRE/DSP-compatible serial interface is straightforward to connect to the backplane microcontroller or to a dedicated isolator such as the ADuM1411, enabling reinforced isolation between the field side and the logic side.
Recommended
Battery Cell Monitoring and Management (BMS)
The AD7708BR-REEL supports battery-cell monitoring because the 8 single-ended or 4 differential inputs can each be routed to a series string of lithium-ion cells through a resistive divider, allowing a single ADC to monitor multiple cells. The 2.7 V to 5.25 V supply range and very low quiescent current make it friendly to battery-powered or battery-backed installations. The programmable gain amplifier and integrated digital filter provide the noise rejection needed at the low update rates typical for BMS applications, where each cell is measured at a few Hz to minimize quiescent draw.
Recommended
Recommended Products Summary
Engineering reference data for AD7708BR-REEL — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | AD7708BR-REEL7 | AD7708BRZ-REEL | AD7718BR-REEL | AD7718BRZ-REEL | AD7708BRUZ-REEL7 | AD7708BRU-REEL |
|---|---|---|---|---|---|---|---|
| Brand | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices |
| Package | 28-SOIC (0.295 inch wide body) | 28-SOIC (0.295 inch wide body) - same | 28-SOIC (0.295 inch wide body) - same | 28-SOIC (0.295 inch wide body) - same | 28-SOIC (0.295 inch wide body) - same | 28-SOIC (0.295 inch wide body) - same | 28-TSSOP (different package, same die) |
| Resolution | 16 bits | 16 bits | 16 bits | 24 bits (pin-compatible upgrade) | 24 bits (pin-compatible upgrade) | 16 bits | 16 bits |
| Input Channels | 8 single-ended / 4 differential (configurable 8/10 pseudo-differential) | 8 / 4 / 10 pseudo-differential | 8 / 4 / 10 pseudo-differential | 8 / 4 / 10 pseudo-differential | 8 / 4 / 10 pseudo-differential | 8 / 4 / 10 pseudo-differential | 8 / 4 / 10 pseudo-differential |
| Supply Voltage | 2.7 V to 5.25 V | 2.7 V to 5.25 V | 2.7 V to 5.25 V | 2.7 V to 5.25 V | 2.7 V to 5.25 V | 2.7 V to 5.25 V | 2.7 V to 5.25 V |
| Programmable Gain | 1 to 128 | 1 to 128 | 1 to 128 | 1 to 128 | 1 to 128 | 1 to 128 | 1 to 128 |
| Serial Interface | SPI / QSPI / MICROWIRE / DSP | SPI / QSPI / MICROWIRE / DSP | SPI / QSPI / MICROWIRE / DSP | SPI / QSPI / MICROWIRE / DSP | SPI / QSPI / MICROWIRE / DSP | SPI / QSPI / MICROWIRE / DSP | SPI / QSPI / MICROWIRE / DSP |
| RoHS / Lead-Free | Matte-tin (lead-bearing, non-RoHS) | Matte-tin (non-RoHS) | Lead-free (RoHS) | Matte-tin (non-RoHS) | Lead-free (RoHS) | Lead-free (RoHS) | Matte-tin (non-RoHS) |
Key Differentiators
- Highest input-channel density in its class on a 28-SOIC wide-body footprint (vs AD7705BRZ-REEL (16-bit, 2-channel sigma-delta ADC))
- Pin-for-pin compatible upgrade path to 24-bit resolution (vs AD7718BR-REEL (24-bit upgrade))
- Factory calibration eliminates user trim steps (vs Generic sigma-delta ADCs without factory calibration)
Design Notes
According to the AD7708 datasheet, AVDD and DVDD must each be decoupled with a 10 uF tantalum in parallel with a 0.1 uF ceramic capacitor placed as close as possible to the supply pins. AGND and DGND should be tied together at a single point near the AD7708, and a wide analog ground plane should be used under the analog inputs. A ferrite bead or small inductor between AVDD and DVDD supplies reduces digital switching noise coupling into the analog front end.
REF IN(+) and REF IN(-) should be driven from a low-noise, low-impedance reference such as the ADR01 (10 V) or AD780 (2.5 V). The AD7708's input-referred noise scales directly with reference noise, so a poor reference will degrade SNR. Place a unity-gain buffer (e.g. AD8628) close to the REF IN pins to prevent reference-voltage sag when the input mux switches between channels with large common-mode swings.
Estimated: do not apply an analog input voltage exceeding AVDD or going below AGND by more than 0.3 V - input currents beyond ~10 mA will latch the on-chip ESD structure and may permanently damage the part. Add 100 ohm series resistors or external clamping diodes at each AIN pin in harsh industrial environments where overvoltage transients are possible. Also ensure the SPI clock rate stays below the AD7708's SCLK specification per the datasheet timing diagram - over-clocking leads to corrupt reads.
Compliance Information
Per Analog Devices part-number scheme, the base AD7708BR-REEL uses matte-tin (lead-bearing) plating and is not RoHS compliant. The lead-free RoHS variant is the AD7708BRZ-REEL. REACH and halogen-free status were not specified in the verified web data. AEC-Q100 is not applicable - AD7708 is a precision industrial ADC, not an automotive-qualified part.
