Analog Devices Inc. AD7711AN

Overview

AD7711AN 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). It is designed for high-accuracy RTD-based temperature measurement in industrial process control systems.

For engineers reviewing the AD7711AN datasheet, AD7711AN pinout, AD7711AN application, or AD7711AN equivalent, this page delivers verified technical context, real-world design meaning of specifications, validated pin functions, confirmed alternative parts with functional distinctions, and supply-chain support details specific to the AD7711AN N-24 plastic DIP package.

Technical Context

The AD7711AN employs a charge-balancing sigma-delta modulator with on-chip digital filtering, where the first notch frequency is software-programmable via its 24-bit control register to adjust filter cutoff (e.g., 10 Hz to 1 kHz) and settling time. Its analog front end includes a 2-channel PGA with selectable gains from 1 to 128, supporting one differential input (AIN1±) and one single-ended input (AIN2).

It integrates two matched 200 µA RTD excitation current sources (RTD1/RTD2), enabling 3-wire and 4-wire RTD configurations with lead resistance cancellation. The device features bidirectional serial interface (SCLK, SDATA, RFS, TFS), SYNC for multi-device synchronization, and internal self-calibration, system calibration, and background calibration modes-all controllable via software.

Key Specifications

Pinout & Package

The AD7711AN is housed in a 24-lead, 0.3-inch-wide plastic dual-in-line package (N-24), compatible with through-hole PCB assembly and socketing for evaluation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7714BN and ADS1248IPWR, the AD7711AN uniquely integrates both RTD excitation and internal reference in a 2-channel architecture - delivering lowest component count and highest integration for dedicated 2-input RTD transmitter designs.

Availability

AD7711AN is available at Aetrix Electronics and suitable for RTD transducer interfaces, smart transmitter modules, and portable industrial instruments requiring stable component supply across extended temperature ranges (–40°C to +85°C).

Supply support for AD7711AN 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, headquartered in Norwood, MA, with decades of expertise in precision data conversion and sensor signal conditioning.

The AD7711AN belongs to Analog Devices' LC²MOS precision sigma-delta ADC family, engineered specifically for low-frequency, high-accuracy industrial measurement applications including RTD, thermocouple, and strain gauge interfacing.

FAQ

What is the operating temperature range of the AD7711AN?

The AD7711AN is rated for operation from –40°C to +85°C (Commercial A-Version). This range is validated per the AD7711AN ordering guide and applies to the N-24 plastic DIP package. Performance specifications such as integral nonlinearity (±0.003% FSR max) and gain drift (2 ppm/°C typ) are guaranteed across this full range when used with AVDD = 5 V ±5%, DVDD = 5 V ±5%, and proper decoupling.

Does the AD7711AN require an external crystal or can it use an external clock?

Yes, the AD7711AN supports both configurations: a crystal can be connected between MCLK IN and MCLK OUT pins, or a CMOS-compatible external clock signal (400 kHz to 10 MHz) can be applied directly to MCLK IN with MCLK OUT left unconnected. The AD7711AN datasheet specifies 10 MHz for 5 V operation and 8 MHz for AVDD > 5.25 V, and the device remains functional down to 400 kHz per characterization data.

How does the AD7711AN handle RTD lead resistance in 3-wire configurations?

The AD7711AN uses its dual 200 µA RTD current sources (RTD1 and RTD2) to cancel lead resistance in 3-wire RTD setups: RTD1 excites the RTD element while RTD2 sources current into the sense lead, enabling measurement of voltage drop across leads only. This technique is explicitly supported in the AD7711AN's functional description and pin documentation, and matching between RTD1/RTD2 currents is specified at ±1% initial tolerance and ≤3 ppm/°C drift.

Can the AD7711AN operate from a single 5 V supply?

Yes, the AD7711AN supports single-supply operation by tying VSS to AGND. In this configuration, analog inputs must remain > –30 mV relative to AGND, and the device maintains full 24-bit no-missing-codes performance with filter notches ≤60 Hz. The AD7711AN datasheet confirms functionality with AVDD = +5 V, DVDD = +5 V, VSS = 0 V, and REF IN(±) = 2.5 V - all standard conditions for single-supply industrial sensor nodes.

What serial interface protocol does the AD7711AN use?

The AD7711AN implements a proprietary 4-wire, microcontroller-compatible serial interface using RFS (receive frame sync), TFS (transmit frame sync), SCLK (serial clock), and SDATA (bidirectional data). It is not SPI or I²C compliant, but functions similarly: RFS initiates read operations, TFS initiates writes, and data is clocked on SCLK edges. All register accesses require 24-bit transfers, and the MODE pin selects between self-clocking (SCLK output) and external-clocking (SCLK input) modes.