Analog Devices Inc. AD676AD

Overview

AD676AD from Analog Devices is a 16-bit successive-approximation analog-to-digital converter (SAR ADC) with on-chip sample-hold, autocalibration, and parallel digital output. It delivers 100 kSPS conversion rate (10 µs total time), ±1 LSB INL (at +25°C), –97 dB THD, and 90 dB S/(N+D) - enabling precision data acquisition in industrial instrumentation and automated test equipment.

For engineers reviewing the AD676AD datasheet, AD676AD pinout, AD676AD application, or AD676AD equivalent, key selection considerations include its –40°C to +85°C extended temperature grade, dual ±12 V / +5 V supply architecture, 28-pin ceramic DIP package, and requirement for external 5–10 V reference voltage to achieve specified dynamic performance.

Technical Context

The AD676AD implements a switched-capacitor charge-redistribution SAR architecture with segmented dual-die construction: an analog BiMOS II chip handles signal conversion and sample-hold, while a DSP CMOS digital controller manages timing, calibration, and output latching. Its autocalibration uses on-chip microcontroller and calibration DAC to measure and correct capacitor mismatch errors across the top nine bits.

Conversion is initiated by a falling edge on SAMPLE after a minimum 2 µs acquisition window; BUSY goes HIGH to indicate active conversion or calibration, and valid 16-bit two's complement data appears on BIT 1–BIT 16 outputs after 17 CLK cycles. The device requires strict separation of AGND and DGND, with AGND SENSE for accurate analog input referencing.

Key Specifications

Pinout & Package

AD676AD is housed in a 28-pin side-brazed ceramic DIP (package option D-28), with separate analog ground (AGND), analog ground sense (AGND SENSE), digital ground (DGND), and isolated power pins for optimal noise immunity.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 16-bit SAR ADC applications.

Compared with AD7606BSTZ and ADS8860IDRCT, the AD676AD provides superior dc accuracy (±2 LSB INL vs. ±3.5 LSB), higher dynamic performance (–97 dB THD vs. –92 dB), and true bipolar input support - making it uniquely suited for laboratory-grade measurement where absolute accuracy and signal fidelity outweigh channel count or power savings.

Availability

AD676AD is available at Aetrix Electronics and suitable for industrial process monitoring, automated test equipment, medical diagnostic instrumentation, and scientific data logging requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for AD676AD 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 Wilmington, MA.

The AD676AD belongs to Analog Devices' legacy precision SAR ADC product line, engineered specifically for high-accuracy, moderate-speed data acquisition in demanding industrial and instrumentation applications where dc precision and dynamic performance must coexist.

FAQ

What is the operating temperature range for the AD676AD?

The AD676AD is rated for operation from –40°C to +85°C (A/B grade), making it suitable for industrial and aerospace applications where ambient conditions exceed commercial-grade limits. This extended range is validated across all ac and dc specifications including INL, THD, and S/(N+D), with no derating required within the specified supply tolerances.

Does the AD676AD require external calibration components?

No, the AD676AD performs full on-chip autocalibration using an internal microcontroller and calibration DAC. It stores correction factors in on-chip RAM to compensate for capacitor mismatch errors. External calibration is unnecessary - only a stable +5 V, ±12 V supply and 5–10 V reference are required to achieve datasheet performance for the AD676AD.

Can the AD676AD operate with a single +5 V supply?

No, the AD676AD requires three independent supplies: +12 V (VCC), –12 V (VEE), and +5 V (VDD). These are not interchangeable or combinable. The analog core depends on the ±12 V rails for full-scale range and linearity; using only +5 V will prevent proper operation and likely damage the device due to violation of absolute maximum ratings.

What is the purpose of the AGND SENSE pin on the AD676AD?

The AGND SENSE pin on the AD676AD provides Kelvin sensing of the analog ground potential at the PCB level, compensating for voltage drop across AGND traces. It must be connected directly to the analog ground plane near the AD676AD's AGND pin - not to DGND or system ground - to maintain <±0.005% FSR bipolar zero error and ensure accurate reference tracking for the AD676AD.

How does the AD676AD handle out-of-range input voltages?

The AD676AD clamps out-of-range inputs to defined saturation codes: VIN > +VREF produces 011...11 (positive overflow), and VIN < –VREF produces 100...00 (negative overflow). This behavior is hardwired and does not cause latch-up or damage. The saturated output allows software detection of overrange conditions without requiring external protection circuitry for the AD676AD.