Analog Devices Inc. AD678AD

Overview

AD678AD from Analog Devices is a complete 12-bit monolithic sampling analog-to-digital converter with integrated sample-hold amplifier, on-chip 5 V reference, clock generation, and microprocessor-compatible bus interface. It delivers 200 kSPS throughput, 1 MHz full-power bandwidth, 72 dB S/N+D (K/B/T grades), ±1 LSB INL, and operates across –40°C to +85°C for industrial instrumentation and data acquisition systems.

For engineers reviewing the AD678AD datasheet, AD678AD pinout, AD678AD application, or AD678AD equivalent, this page provides verified technical context, validated pin functions, real-world timing behavior, confirmed DC/AC specifications, and two rigorously cross-checked alternative parts for measurement-grade ADC selection.

Technical Context

The AD678AD employs a recursive subranging architecture combining flash conversion stages with error correction logic to achieve 12-bit resolution at 200 kSPS. Its sample-hold amplifier supports 1 µs input settling time and 150 ps aperture jitter, enabling accurate digitization of fast-slewing signals up to 1 MHz.

It features dual digital interface modes: 12-bit parallel output (via DB11–DB0) or 8-bit multiplexed output (DB11–DB4 with R/L and HBE control), both TTL/5 V CMOS compatible. Internal BiMOS process integrates high-precision bipolar analog circuits with low-power CMOS logic and laser-trimmed thin-film resistors.

Key Specifications

Pinout & Package

AD678AD is housed in a 28-lead ceramic DIP (package option D-28) with 0.6-inch width, through-hole mounting, and hermetic sealing suitable for harsh environments.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 12-bit sampling ADC applications.

Compared with AD678BD, AD678AD trades guaranteed DC linearity for lower cost and qualification at the same industrial temperature grade; versus ADS7800KP, it delivers plug-and-play integration at the expense of maximum sampling rate - making AD678AD optimal for compact, self-contained data loggers where ease of design and thermal robustness outweigh raw speed.

Availability

AD678AD is available at Aetrix Electronics and suitable for industrial process monitoring, automated test equipment, avionics data recorders, and power quality analyzers requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for AD678AD 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 DSP ICs, founded in 1965 and headquartered in Wilmington, MA.

The AD678AD belongs to Analog Devices' precision data acquisition product line, engineered for applications demanding integrated signal conditioning, guaranteed AC/DC performance, and rugged packaging - particularly in industrial control, instrumentation, and defense systems.

FAQ

What is the operating temperature range of the AD678AD?

The AD678AD is rated for –40°C to +85°C operation, matching the "A" and "B" grade industrial temperature specification. This range is validated across all AC performance parameters including S/N+D, THD, and full-power bandwidth, making it suitable for deployment in factory floors, outdoor enclosures, and vehicle-mounted test systems without derating.

Does the AD678AD require external calibration components?

The AD678AD is factory laser-trimmed and requires no external calibration for standard operation. In unipolar mode, only a single 50 Ω ±1% resistor between BIPOFF and AGND is needed; in bipolar mode, two 50 Ω resistors (one each for BIPOFF and REFIN) suffice. Trim pots are optional and only necessary if ±1 LSB INL or ±4 LSB gain error must be further reduced beyond factory specs.

How does the AD678AD handle digital interface timing in 8-bit mode?

In 8-bit mode (12/8 = LOW), the AD678AD outputs its 12-bit result across two consecutive 8-bit bus cycles. The R/L pin selects left or right justification, while HBE (DB0) controls byte order: HBE = LOW reads the high byte first, then the low byte. Access time tBA is 10 ns min, and read pulsewidth tRP is 97 ns - compatible with standard 80C31 and 80C51 microcontrollers.

Can the AD678AD operate with a single +5 V supply?

No. The AD678AD requires three separate supplies: +12 V (VCC), –12 V (VEE), and +5 V (VDD). These are not interchangeable - VCC and VEE power the analog signal path and sample-hold amplifier, while VDD powers digital logic and output drivers. Attempting single-supply operation will cause functional failure and potential damage due to violation of absolute maximum ratings.

What is the significance of the SYNC pin configuration on the AD678AD?

The SYNC pin determines timing governance: tied to VDD enables synchronous mode where SC and EOC are gated by CS, ensuring deterministic bus arbitration; tied to DGND enables asynchronous mode where SC operates independently of CS, allowing continuous conversion triggered solely by SC pulses. Asynchronous mode requires an external 3 kΩ pull-up on EOC, while synchronous mode uses internal three-state drive.