Analog Devices Inc. AD7711AR

Overview

AD7711AR from Analog Devices is a 24-bit charge-balancing sigma-delta ADC with integrated programmable gain amplifier (PGA), dual RTD excitation current sources (200 µA each), and on-chip 2.5 V reference. It supports differential and single-ended analog inputs, offers ±0.0015% integral nonlinearity, and operates from single or dual supplies (AVDD = 5–10 V, VSS = 0 or –5 V) for RTD-based temperature measurement systems.

For engineers reviewing the AD7711AR datasheet, AD7711AR pinout, AD7711AR application, or AD7711AR equivalent, this device is selected for high-accuracy, low-drift industrial sensor signal conditioning-particularly in 3-/4-wire RTD transmitters where on-chip excitation, self-calibration, and filter notch programming (10–1000 Hz) directly impact system-level accuracy and calibration workflow.

Technical Context

The AD7711AR employs a proprietary charge-balancing modulator followed by a programmable digital low-pass filter whose first notch frequency (10 Hz to 1 kHz) is set via the 24-bit control register. Its two-channel front end includes a differential input (AIN1±) with PGA gains of 1–128 and a single-ended input (AIN2), both referenced to a configurable differential reference (REF IN±).

It integrates two matched 200 µA RTD excitation sources (RTD1/RTD2), a burnout detection current (4.5 µA), and bidirectional serial interface (SCLK/MODE/TFS/RFS/SDATA/DRDY) supporting both self-clocking and external clocking modes. Calibration is performed via on-chip registers enabling self-, system-, and background calibration without external hardware.

Key Specifications

Pinout & Package

AD7711AR is housed in a 24-lead SOIC package (R-24), 0.3-inch wide, RoHS-compliant, with standard JEDEC MS-013 footprint.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-precision sigma-delta ADC applications.

Compared with AD7714BRUZ and ADS1248IPWR, the AD7711AR uniquely combines matched 200 µA RTD excitation, on-chip 2.5 V reference, and burnout detection in a single SOIC package-making it optimal for fixed-function, high-stability RTD transmitters where calibration integrity and analog integration outweigh channel count or power savings.

Availability

AD7711AR is available at Aetrix Electronics and suitable for RTD transmitters, smart process instruments, and portable industrial analyzers requiring stable component supply across extended temperature ranges (–40°C to +85°C) and long-lifecycle production.

Supply support for AD7711AR 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 is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, founded in 1965 and headquartered in Wilmington, MA.

The AD7711AR belongs to Analog Devices' precision sigma-delta ADC product line, designed specifically for high-accuracy, low-drift industrial sensor signal conditioning-especially in RTD, thermocouple, and bridge-based measurement systems demanding ratiometric operation and on-chip calibration.

FAQ

What is the operating temperature range for the AD7711AR?

The AD7711AR is rated for –40°C to +85°C (Commercial A-version). This range is validated per the AD7711AR ordering guide and applies to all electrical specifications including INL (±0.003% FSR max), gain drift (2 ppm/°C), and RTD current matching (±1% at 25°C). Operation outside this range requires validation against the S-version (AD7711SQ, –55°C to +125°C) or derating analysis.

Does the AD7711AR support both unipolar and bipolar input configurations?

Yes, the AD7711AR supports both configurations via the B/U bit in its 24-bit control register. When B/U = 1, it operates in unipolar mode with 0 to +VREF input range; when B/U = 0, it operates in bipolar mode with ±VREF range. The output coding is natural binary for unipolar and offset binary for bipolar-both fully supported in the AD7711AR's digital filter and data register architecture.

How does the AD7711AR handle RTD lead resistance compensation?

The AD7711AR enables 3-wire RTD compensation by driving RTD1 and RTD2 currents through separate pins and routing them to different RTD legs. By measuring the voltage drop across the sense leads while exciting only one leg at a time-and using the known ratio of RTD1/RTD2 currents-the AD7711AR allows software to compute and subtract lead resistance error. This method is explicitly supported in the AD7711AR's functional description and pin function table.

Can the AD7711AR operate from a single 5 V supply?

Yes, the AD7711AR can operate from a single 5 V supply by tying VSS to AGND. In this configuration, analog inputs must remain ≥ –30 mV relative to VSS, and the input common-mode range becomes 0 V to AVDD. The device maintains full 24-bit no-missing-codes performance and ±0.0015% INL at 25°C, as confirmed in the AD7711AR datasheet's "Single-Supply Operation" section and power requirements table.

What is the purpose of the VBIAS pin on the AD7711AR?

The VBIAS pin on the AD7711AR sets the internal analog common-mode voltage level. It must be biased between VSS + 0.85×VREF and AVDD – 0.85×VREF (e.g., 2.5 V when AVDD = 5 V, VSS = 0 V). Proper VBIAS setting improves PSRR (up to 95 dB) and ensures optimal modulator linearity-critical for maintaining the AD7711AR's ±0.0015% INL specification across temperature and supply variations.