Analog Devices Inc. AD7711AAR

Overview

AD7711AAR from Analog Devices is a 24-bit sigma-delta analog-to-digital converter with integrated programmable gain amplifier (PGA), dual differential inputs, on-chip 2.5 V reference, and 400 µA RTD excitation current source. It delivers ±0.0015% integral nonlinearity, 100 dB CMR at DC, and operates from single or dual supplies (AVDD = 5–10 V, VSS = 0 or –5 V). It is designed for precision RTD-based temperature measurement systems requiring low-noise, high-resolution digitization of low-level transducer signals.

For engineers reviewing the AD7711AAR datasheet, AD7711AAR pinout, AD7711AAR application, or AD7711AAR equivalent, key selection considerations include its 24-bit no-missing-codes performance, software-configurable filter notch (10–500 Hz), PGA gain range (1–128), bidirectional serial interface, and built-in self/system/background calibration modes - all critical for industrial sensor signal conditioning in microcontroller-based systems.

Technical Context

The AD7711AAR employs a charge-balancing sigma-delta architecture with an auto-zeroed modulator and on-chip digital filter whose first notch frequency is programmable via control register bits FS0–FS11. Its two-channel differential input multiplexer supports main/auxiliary channel switching under software control, enabling periodic system diagnostics or dual-sensor monitoring without external hardware.

It integrates a 400 µA RTD excitation current source with programmable enable/disable, a 2.5 V buffered reference output (±1% initial tolerance, 20 ppm/°C drift), and VBIAS bias voltage input to stabilize common-mode operation across supply configurations. The device supports both self-clocking (SCLK output) and external clocking (SCLK input) serial interface modes via the MODE pin.

Key Specifications

Pinout & Package

The AD7711AAR is housed in a 24-lead SOIC (RW-24) package with 0.3-inch width and standard JEDEC outline.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7711AAR, AD7792BRUZ offers smaller footprint and lower quiescent current but requires external excitation circuitry, while ADS1248IPWR provides greater RTD drive strength and speed at the cost of distinct noise-performance trade-offs and calibration workflow differences.

Availability

AD7711AAR is available at Aetrix Electronics and suitable for industrial temperature monitoring, smart sensor transmitters, and multi-channel data acquisition systems requiring stable component supply, long-term lifecycle support, and traceable sourcing for production programs.

Supply support for AD7711AAR 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, serving industrial, automotive, communications, and healthcare markets.

The AD7711AAR belongs to Analog Devices' precision sigma-delta ADC product line, engineered specifically for low-frequency, high-accuracy sensor signal conditioning in RTD, thermistor, and strain-gauge applications where resolution, stability, and integrated features reduce system complexity.

FAQ

What is the maximum allowed master clock frequency for AD7711AAR?

The AD7711AAR supports a master clock (MCLK IN) frequency up to 10 MHz when AVDD = 5 V ±5%. For AVDD between 5.25 V and 10.5 V, the maximum clock is 8 MHz. Operation at 400 kHz is guaranteed across the full temperature range. Exceeding these limits may cause incorrect conversion results or increased power consumption in the AD7711AAR.

Does AD7711AAR support bipolar input ranges?

Yes, the AD7711AAR supports bipolar input ranges via the B/U bit in its control register. When B/U = 0, the input range is ±VREF/GAIN, enabling measurement of both positive and negative differential voltages relative to AIN(–). This mode is commonly used with bridge sensors or offset-corrected transducer outputs in the AD7711AAR.

Can AD7711AAR operate from a single 5 V supply?

Yes, the AD7711AAR 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 unipolar input range is 0 to +VREF/GAIN. For bipolar operation or extended negative input range, a dual supply (e.g., AVDD = +5 V, VSS = –5 V) is required in the AD7711AAR.

How does the AD7711AAR handle RTD burnout detection?

The AD7711AAR implements RTD burnout detection using a 4.5 mA current source connected to AIN1(+). When enabled via the control register, this current flows through the RTD; an open circuit causes AIN1(+) to rise toward AVDD, producing a full-scale output code. This diagnostic feature is independent of the main 400 µA excitation current in the AD7711AAR.

What is the purpose of the VBIAS pin on AD7711AAR?

The VBIAS pin on the AD7711AAR sets the common-mode voltage for the analog input stage. It must satisfy VBIAS ± 0.85 × VREF ∈ [VSS, AVDD]. Proper VBIAS selection (e.g., tied to REF OUT for +5 V/0 V supply) ensures optimal CMR and prevents clipping. Incorrect VBIAS degrades performance and may cause conversion errors in the AD7711AAR.