Analog Devices Inc. AD7718BR

Overview

AD7718BR from Analog Devices is a 24-bit Σ-Δ analog-to-digital converter (ADC) with integrated programmable-gain amplifier (PGA), 10-channel pseudo-differential or 5-channel fully differential input configuration, on-chip 32.768 kHz crystal oscillator and PLL, and 3-wire SPI-compatible serial interface - designed for high-precision industrial sensor signal acquisition in single 3 V or 5 V supply systems.

For engineers reviewing the AD7718BR datasheet, AD7718BR pinout, AD7718BR application, or AD7718BR equivalent, key selection considerations include its 24-bit no-missing-codes resolution, simultaneous 50/60 Hz rejection, VREF Select™ ratiometric/absolute measurement capability, CHOP mode for enhanced noise performance, and pin compatibility with the 16-bit AD7708BR for scalable system design.

Technical Context

The AD7718BR implements a sigma-delta modulation architecture with a 2nd-order modulator and digital filter providing selectable output data rates from 5.4 Hz to 1.365 kHz. Its dual-mode operation-CHOP = 0 (optimized analog performance, 13–18 bits peak-to-peak resolution) and CHOP = 1 (optimized throughput, up to 1.365 kHz update rate)-enables trade-off control between noise floor and channel scan speed.

It integrates rail-to-rail input buffers, a 2-bit configurable I/O port, factory-calibrated offset/gain registers, and supports both unipolar (offset binary) and bipolar (two's complement) output coding. Reference inputs REFIN1(±) and REFIN2(±) are software-configurable, enabling flexible ratiometric or absolute measurement topologies without external components.

Key Specifications

Pinout & Package

AD7718BR is housed in a 28-lead SOIC package (R-28), with exposed pad not electrically connected. Pin functions are validated per Analog Devices AD7708/AD7718 Rev. 0 datasheet, Section "PIN FUNCTION DESCRIPTIONS".

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7708BR and ADS1256IDBT, the AD7718BR uniquely combines 24-bit metrology-grade resolution, on-chip oscillator + PLL, simultaneous 50/60 Hz rejection, and dual-reference VREF Select™ - making it optimal for low-power, noise-immune, multi-sensor industrial measurement where hardware simplicity and global EMI resilience are mandatory.

Availability

AD7718BR 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 traceable sourcing.

Supply support for AD7718BR 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, serving industrial, automotive, communications, and healthcare markets since 1965.

The AD7718BR belongs to Analog Devices' precision sigma-delta ADC product line, engineered specifically for low-frequency, high-accuracy sensor signal conditioning in harsh electrical environments - emphasizing noise immunity, calibration stability, and system-level integration.

FAQ

What is the maximum achievable peak-to-peak resolution of the AD7718BR and under what conditions?

The AD7718BR achieves up to 18 bits peak-to-peak resolution when configured in CHOP mode (CHOP = 0) at a 20 Hz output data rate with a ±2.56 V input range and gain setting of 69. This is confirmed in the AD7718 specifications table (Rev. 0, p.4) and reflects effective dynamic range after noise averaging - critical for resolving microvolt-level signals from precision transducers. The AD7718BR maintains this performance without external filtering or calibration.

Does the AD7718BR require an external crystal, or does it include an oscillator?

The AD7718BR includes an on-chip crystal oscillator buffer and PLL that accept a standard 32.768 kHz tuning-fork crystal connected to XTAL1/XTAL2 pins. No external clock generator or oscillator IC is needed - the internal circuitry generates all required internal clocks. This is explicitly stated in the General Description (p.1) and confirmed in the Timing Characteristics section (p.9), where t1 = 32.768 kHz typ is specified as the crystal oscillator frequency.

Can the AD7718BR interface directly with a 3.3 V microcontroller SPI bus?

Yes - the AD7718BR supports 3 V digital operation (DVDD = 2.7–3.6 V), and its digital I/O pins (DIN, DOUT, SCLK, CS, RDY) meet 3.3 V logic thresholds: VINH ≥ 2.0 V (min), VINL ≤ 0.4 V (max) at DVDD = 3 V. The Schmitt-triggered SCLK input further enhances noise immunity. All timing parameters in the datasheet (e.g., t5 = 80 ns max for DOUT valid delay) are validated at 3 V, confirming reliable interoperability with 3.3 V MCUs.

How does the VREF Select™ feature work on the AD7718BR?

VREF Select™ allows the AD7718BR to operate in either ratiometric mode (using the same reference for excitation and ADC conversion) or absolute mode (using separate references) by configuring which REFIN pair (REFIN1 or REFIN2) serves as the ADC reference. Both REFIN1(±) and REFIN2(±) accept 1 V to AVDD differential voltages (nominal 2.5 V), and their common-mode range extends beyond supply rails (AGND–30 mV to AVDD+30 mV). This is detailed in the "REFERENCE INPUTS" specification tables (pp.3–4, 6–7) and General Description (p.1).

Is the AD7718BR pin-compatible with any other Analog Devices ADCs?

Yes - the AD7718BR is pin-for-pin compatible with the AD7708BR, as explicitly stated in the General Description (p.1): "Both parts are pin-for-pin compatible allowing an upgradable path from 16 to 24 bits without the need for hardware modifications." This includes identical 28-lead SOIC (R-28) packaging, matching pin functions (e.g., AIN1–AIN10, REFIN1/2, serial interface), and register-level compatibility - enabling seamless migration within the same PCB footprint.