Analog Devices Inc. AD7711ARZ

Overview

AD7711ARZ from Analog Devices is a 24-bit sigma-delta analog-to-digital converter with integrated programmable-gain amplifier (PGA), dual RTD excitation current sources (200 µA each), internal 2.5 V reference, and bidirectional serial interface. It supports differential and single-ended inputs, operates from 5 V to 10 V AVDD with optional dual-supply (VSS = –5 V), and delivers ±0.0015% integral nonlinearity at ≤60 Hz filter notch for high-accuracy RTD-based temperature measurement in industrial transmitters.

For engineers reviewing the AD7711ARZ datasheet, AD7711ARZ pinout, AD7711ARZ application, or AD7711ARZ equivalent, key selection considerations include its 24-bit no-missing-codes performance, on-chip self/system/background calibration, programmable filter cutoffs (10–500 Hz), 1–128 PGA gain range, and support for 3-/4-wire RTD configurations without external excitation circuitry.

Technical Context

The AD7711ARZ employs a charge-balancing sigma-delta modulator with on-chip digital filtering, where the first notch frequency is software-programmable via the 24-bit control register. Its analog front end includes a two-channel input multiplexer, one differential (AIN1±) and one single-ended (AIN2), both routed through a PGA with selectable gains of 1–128.

It integrates two matched 200 µA RTD excitation current sources (RTD1/RTD2), a 2.5 V buffered reference output (REF OUT), and bias voltage input (VBIAS) for optimal common-mode setting. The device supports both self-clocking (SCLK output) and external clocking modes via MODE and SCLK pins, enabling flexible microcontroller interfacing.

Key Specifications

Pinout & Package

AD7711ARZ is housed in a 24-lead SOIC package (R-24), 0.3-inch wide, RoHS-compliant, with exposed pad not electrically connected. Pin functions are validated per Analog Devices AD7711 datasheet Rev. G.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7711ARZ, AD7714BRUZ trades integrated RTD excitation for additional input channels, while ADS1248IPWR provides broader current selection and superior INL but requires external reference routing and layout - making AD7711ARZ optimal for compact, self-contained RTD transmitters where reference integration and proven field reliability are prioritized.

Availability

AD7711ARZ is available at Aetrix Electronics and suitable for RTD transmitters, smart process analyzers, and portable industrial instruments requiring stable component supply, long-lifecycle support, and verified calibration performance across –40°C to +85°C.

Supply support for AD7711ARZ 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, founded in 1965 and headquartered in Wilmington, MA.

The AD7711ARZ belongs to Analog Devices' precision sigma-delta ADC product line, designed specifically for low-frequency industrial sensor signal conditioning - emphasizing integrated RTD excitation, on-chip calibration, and ratiometric measurement architecture for metrology-grade accuracy.

FAQ

What is the maximum sampling rate of the AD7711ARZ at 24-bit resolution?

The AD7711ARZ achieves 24-bit no-missing-codes performance up to 100 SPS when configured with a 10 Hz digital filter notch. At higher notches (e.g., 500 Hz), resolution drops to 15 bits. Its input sampling rate is fixed at f_{CLK_IN}/256; with a 10 MHz master clock, this yields 39.06 kSPS raw sampling, but effective output data rate is determined solely by filter configuration. The AD7711ARZ does not support oversampling beyond its built-in filter settings.

Can the AD7711ARZ operate with a single 5 V supply?

Yes, the AD7711ARZ supports single-supply operation: tie VSS to AGND and use AVDD = 5 V. In this configuration, the analog input range is unipolar (0 to +V_REF/gain) for AIN1(+) and AIN2, with minimum input voltage ≥ –30 mV relative to VSS. For bipolar operation or extended negative range, connect VSS to –5 V - enabling inputs down to –V_REF/gain. The AD7711ARZ's dual-supply capability is confirmed in the Absolute Maximum Ratings and General Description sections of its datasheet.

How does the AD7711ARZ handle RTD lead resistance in 3-wire configurations?

The AD7711ARZ supports 3-wire RTD compensation using its dual 200 µA current sources (RTD1 and RTD2) and differential input AIN1(±). RTD1 excites the RTD; RTD2 sources current into the AIN1(–) node, canceling voltage drop across the lead wire between RTD and AIN1(–). This technique requires no external switching or calibration - the AD7711ARZ implements it entirely in hardware, with matching between RTD1/RTD2 currents specified at ±1% initial tolerance and 3 ppm/°C drift tracking.

Is the internal 2.5 V reference of the AD7711ARZ suitable as an excitation source for RTDs?

Yes, the AD7711ARZ's REF OUT pin provides a buffered 2.5 V ±1% reference capable of sourcing up to 1 mA, making it suitable to bias 100 Ω or 1000 Ω RTDs directly. When used with the internal 200 µA excitation currents, this creates a fully ratiometric system: ADC output depends only on RTD resistance / reference resistance ratio, inherently rejecting drift in both the reference voltage and excitation current. This configuration is explicitly supported in the AD7711ARZ's application examples and General Description.

What calibration modes does the AD7711ARZ support, and how are they initiated?

The AD7711ARZ supports three calibration modes: self-calibration (zero and full-scale), system calibration (using user-provided reference voltages), and background calibration (continuous zero correction during normal operation). All are controlled via bit fields in the 24-bit control register - MD2:MD0 bits select mode, and PD bit initiates calibration. Self-calibration takes ~200 ms and requires no external connections; system calibration requires applying precise voltages to AIN1(±) and is triggered by writing to the control register. The AD7711ARZ confirms completion via DRDY pin pulse and status bits.