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Analog Devices Inc. AD7708BRZ
- Part No.:
- AD7708BRZ
- Manufacturer:
- Analog Devices Inc.
- Category:
- Analog to Digital Converters (ADC)
- Package:
- 28-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
AD7708BRZ.pdf
- Description:
- IC ADC 16BIT SIGMA-DELTA 28SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:785
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Product details
Overview
AD7708BRZ from Analog Devices is a 16-bit, 8-/10-channel Σ-Δ analog-to-digital converter optimized for low-frequency industrial measurement. It integrates a programmable gain amplifier (gain 1–128), on-chip 32.768 kHz crystal oscillator with PLL, rail-to-rail input buffers, and a 2-bit digital I/O port. It operates from single 3 V or 5 V supplies and supports simultaneous 50 Hz/60 Hz rejection - ideal for pressure transducer signal acquisition in smart transmitters.
For engineers reviewing the AD7708BRZ datasheet, AD7708BRZ pinout, AD7708BRZ application, or AD7708BRZ equivalent, key selection considerations include its 16-bit no-missing-codes resolution, CHOP mode vs. non-CHOP trade-off (13–16 bits p-p at 5.4–1.365 kHz), VREF Select™ for ratiometric/absolute measurement, and pin compatibility with the 24-bit AD7718 for scalable system design.
Technical Context
The AD7708BRZ implements a sigma-delta modulation architecture with a 3rd-order modulator and programmable digital filter. Its analog front-end includes a fully differential PGA and configurable input multiplexer supporting up to 10 pseudo-differential or 5 fully differential channels, with two pins (REFIN2+/AIN9 and REFIN2−/AIN10) dual-function as reference inputs or analog inputs.
It features dual power domains (AVDD/DVDD), Schmitt-triggered SCLK for noise immunity, and three operating modes: normal conversion, power-down (30 µA with oscillator running), and standby (2 µA with oscillator off). Calibration is supported via self-calibration and system calibration registers, with offset error reduced to ±0.65 LSB after self-calibration.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Resolution | 16-bit no-missing-codes; 13–16 bits peak-to-peak depending on gain and output data rate (e.g., 16 bits p-p at ±2.56 V range, 20 Hz update) |
| Input Channels | 8 pseudo-differential or 10 pseudo-differential inputs (AIN1–AIN10 + AINCOM); configurable as 4/5 fully differential pairs |
| PGA Gain Range | 1 to 128 in binary steps; enables direct digitization of signals from 20 mV to 2.56 V full-scale without external amplification |
| Simultaneous Rejection | 100 dB min @ 50 Hz and 60 Hz (CHOP disabled, SF Word = 68/82); eliminates need for external notch filtering in AC-line-noise environments |
| Power Consumption | 1.28 mA typ @ 3 V (normal mode); 30 µA max @ 3 V with 32.768 kHz oscillator active (power-down mode) |
| Reference Flexibility | VREF Select™ allows use of internal 2.5 V reference or external reference (1 V to AVDD); supports both ratiometric sensor interfaces and absolute voltage measurements |
| Output Data Rate | Software-programmable from 5.4 Hz (CHOP enabled) to 1.365 kHz (CHOP disabled); enables optimization for noise performance or throughput |
Pinout & Package
The AD7708BRZ is housed in a 28-lead SOIC package (R-28), with exposed pad not electrically connected. Pin functions are defined per Analog Devices' AD7708/AD7718 Rev. 0 datasheet, Section "PIN FUNCTION DESCRIPTIONS".
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| AIN1–AIN10 | Analog Input | Programmable-gain inputs; AIN1–AIN8 support pseudo- or fully-differential configurations; AIN9/AIN10 are dual-function (REFIN2+/− or AIN9/10) |
| AINCOM | Common Analog Input | Reference node for pseudo-differential operation; voltage range: AGND −30 mV to AVDD +30 mV (NEGBUF = 0) |
| REFIN1(±), REFIN2(±) | Reference Inputs | Dual reference inputs support independent ratiometric measurement paths; nominal 2.5 V differential, 1 V to AVDD range |
| AVDD, DVDD | Supply Rails | Independent analog (AVDD) and digital (DVDD) supplies (2.7–3.6 V or 4.75–5.25 V); improves PSR and noise isolation |
| SCLK, DIN, DOUT, CS, RDY | Serial Interface | 3-wire SPI/QSPI/MICROWIRE-compatible interface; Schmitt-triggered SCLK ensures robust timing in noisy environments |
| P1, P2 | Digital I/O Port | 2-bit general-purpose bidirectional port; logic levels referenced to AVDD/AGND per datasheet Note 5 |
| RESET | Asynchronous Reset | Active-low reset; minimum pulse width 50 ns; initiates power-on reset sequence and register initialization |
Key Features
| Feature | Design Value |
|---|---|
| Factory-calibrated architecture | Eliminates need for user calibration in most applications; INL ±15 ppm FSR, offset error ±0.65 LSB after self-calibration |
| CHOP mode (CHOP = 0) | Enables ultra-low drift performance: offset drift ±10 nV/°C, 100 dB CMR @ DC and 50/60 Hz, ideal for high-precision DC measurements |
| VREF Select™ technology | Allows dynamic switching between ratiometric (e.g., bridge sensors) and absolute (e.g., thermocouple) measurement modes using same hardware |
| Rail-to-rail input buffer | Supports analog inputs from AGND +100 mV to AVDD −100 mV (NEGBUF = 1), enabling direct connection to low-output sensors |
| Single-cycle conversion setting | Reduces configuration overhead: each write to Mode Register sets update rate, filter, and operation mode in one transaction |
Applications
| Pressure Transducer Interface | Smart Industrial Transmitter |
|---|---|
Use Scenario: Digitizing millivolt-level outputs from strain-gauge-based pressure sensors in hazardous-area field devices. IC Role / Device Role / Timing Role: ADC front-end with integrated PGA and 50/60 Hz rejection; performs synchronized sampling and digital filtering before HART or RS-485 transmission. Use Value: Eliminates external instrumentation amplifier and line-frequency notch filters; reduces BOM count and PCB area while maintaining 16-bit accuracy under AC mains interference. | Use Scenario: Multi-sensor data acquisition in programmable logic controller (PLC) analog input modules with local signal conditioning. IC Role / Device Role / Timing Role: 8-channel Σ-Δ ADC with configurable input routing and on-chip reference; manages time-multiplexed sampling across temperature, flow, and level sensors. Use Value: Enables channel throughput up to 1.365 kHz (non-CHOP) or 105 Hz (CHOP) with consistent 16-bit resolution - sufficient for <100 Hz control loop sampling. |
| Portable Instrumentation | Combined Ratiometric/Absolute System |
Use Scenario: Battery-powered handheld multimeter acquiring DC voltage, current, and resistance with auto-ranging. IC Role / Device Role / Timing Role: Low-power ADC with 3 V operation, 30 µA power-down mode, and internal oscillator - removes need for external clock source or power management IC. Use Value: Extends battery life beyond 100 hours; supports precision measurement down to 20 mV full-scale without external gain stages. | Use Scenario: Single-board system measuring both 4–20 mA loop current (ratiometric) and auxiliary thermistor voltage (absolute) simultaneously. IC Role / Device Role / Timing Role: Dual-reference-capable ADC using REFIN1 for loop-powered sensor and REFIN2 for thermistor; VREF Select™ enables software-switched reference paths. Use Value: Reduces component count by consolidating two independent measurement chains into one IC; avoids reference crosstalk and layout complexity. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar ADC applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AD7718BRZ | 24-bit resolution, identical pinout and register map; higher noise performance (13–18 bits p-p), lower offset drift (±10 nV/°C CHOP) | Required for sub-ppm precision metrology; not suitable where 16-bit resolution suffices and cost/power are constrained | Select AD7718BRZ only when 24-bit resolution and enhanced 50/60 Hz rejection (110 dB typ) are mandatory for the target accuracy class. |
| ADS124S08IPWR | 24-bit, 4-channel, integrated PGA and reference; SPI interface; lower power (0.38 mA typ @ 3 V), but no dual-reference or VREF Select™ | Lacks dual-reference flexibility and 8+ channel count; better suited for compact, low-channel-count sensor nodes | Choose ADS124S08IPWR for space-constrained designs needing integrated reference and lower quiescent current, but accept loss of ratiometric/absolute dual-mode capability. |
Compared with AD7718BRZ, the AD7708BRZ trades resolution and drift performance for lower cost and power; compared with ADS124S08IPWR, it offers superior channel density and reference flexibility at the expense of higher active current and absence of integrated reference.
Availability
AD7708BRZ is available at Aetrix Electronics and suitable for industrial process control, portable instrumentation, and smart transmitter designs requiring stable component supply, long-term lifecycle support, and guaranteed traceability.
Supply support for AD7708BRZ includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
Analog Devices, Inc. is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, headquartered in Norwood, MA.
The AD7708BRZ belongs to Analog Devices' precision Σ-Δ ADC product line, designed specifically for low-frequency, high-accuracy measurement in harsh industrial environments - emphasizing noise immunity, calibration stability, and flexible sensor interfacing.
FAQ
What is the maximum sample rate of the AD7708BRZ in non-CHOP mode?
The AD7708BRZ achieves a maximum output update rate of 1.365 kHz in non-CHOP (CHOP = 1) mode. This rate is achieved with minimal digital filter settling and is suitable for applications requiring higher channel throughput, such as multi-sensor polling in PLC analog input modules. At this rate, peak-to-peak resolution is 16 bits for a ±2.56 V input range with appropriate gain setting. The AD7708BRZ maintains no missing codes across its full 16-bit range regardless of update rate.
Does the AD7708BRZ support both ratiometric and absolute measurements?
Yes, the AD7708BRZ supports both ratiometric and absolute measurements via its VREF Select™ feature. It provides two independent reference inputs (REFIN1 and REFIN2), each configurable for separate sensor channels. When used with a bridge sensor, REFIN1 can be tied to the excitation voltage for ratiometric operation; REFIN2 can connect to a precision 2.5 V reference for absolute thermistor or voltage measurements. This dual-reference capability is implemented in hardware and requires no external components - a core differentiator of the AD7708BRZ.
What is the power consumption of the AD7708BRZ in power-down mode?
In power-down mode with the 32.768 kHz oscillator still running, the AD7708BRZ consumes a maximum of 30 µA at DVDD = 5 V and 10 µA at DVDD = 3 V. If the oscillator is powered down, consumption drops further to 8 µA (5 V) or 2 µA (3 V). These values reflect total device current (DIDD + AIDD). The fast wake-up time of 1 ms from power-down enables efficient duty-cycled operation in battery-powered instrumentation without sacrificing measurement readiness.
How many analog input channels does the AD7708BRZ support, and how are they configured?
The AD7708BRZ supports up to 10 analog input terminals: AIN1 through AIN10 plus AINCOM. These can be configured as 8 pseudo-differential channels (e.g., AIN1–AINCOM, AIN2–AINCOM, ..., AIN8–AINCOM) or 5 fully differential channels (e.g., AIN1–AIN2, AIN3–AIN4, ..., AIN9–AIN10). Pins AIN9 and AIN10 are dual-function: they serve as REFIN2(+) and REFIN2(−) by default but can be reconfigured as analog inputs via the ADC Control Register. This flexibility allows adaptation to diverse sensor topologies without board redesign.
Is the AD7708BRZ pin-compatible with any other Analog Devices ADCs?
Yes, the AD7708BRZ is pin-for-pin compatible with the AD7718BRZ - a 24-bit version in the same family. Both share identical pinout, register map, serial interface protocol, and package options (28-lead SOIC and TSSOP). This compatibility enables seamless hardware upgrade paths: a system designed for the AD7708BRZ can migrate to the AD7718BRZ for higher resolution without PCB layout changes, provided firmware accommodates extended data words and updated noise performance characteristics.
AD7708BRZ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 28-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tube
- Product Status:
- Active
- Number of Bits:
- 16
- Sampling Rate (Per Second):
- 1.37k
- Number of Inputs:
- 4, 8
- Input Type:
- Differential, Pseudo-Differential, Single Ended
- Data Interface:
- SPI, DSP
- Configuration:
- MUX-PGA-ADC
- Ratio - S/H:ADC:
- -
- Number of A/D Converters:
- 1
- Architecture:
- Sigma-Delta
- Reference Type:
- External
- Voltage - Supply, Analog:
- 2.7V ~ 3.3V, 5V
- Voltage - Supply, Digital:
- 2.7V ~ 3.3V, 5V
- Features:
- PGA
- Operating Temperature:
- -40°C ~ 85°C
- Supplier Device Package:
- 28-SOIC
- Mounting Type:
- Surface Mount
- Grade:
- -
- Qualification:
- -
AD7708BRZ FAQ
1.How can I place an order for AD7708BRZ through Aetrix?
Please submit a Request for Quotation (RFQ) for AD7708BRZ on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for AD7708BRZ reliable?
The price and inventory of AD7708BRZ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AD7708BRZ is usually 5 days.
3.What payment methods are accepted for AD7708BRZ?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AD7708BRZ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AD7708BRZ?
AD7708BRZ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AD7708BRZ order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for AD7708BRZ?
For technical support, including AD7708BRZ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AD7708BRZ requirements.
6.How does Aetrix verify that AD7708BRZ is sourced from the original manufacturer or authorized distributors?
All AD7708BRZ products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that AD7708BRZ meets industry standards.
7.What is the process for return or replacement of AD7708BRZ?
All AD7708BRZ units undergo pre-shipment inspection (PSI). If there is an issue with AD7708BRZ, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The AD7708BRZ part is unused and in its original packaging.
Return procedure for AD7708BRZ:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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