Analog Devices Inc. AD774BAR

Overview

AD774BAR from Analog Devices is a complete monolithic 12-bit successive-approximation analog-to-digital converter with on-chip 10 V reference, clock, and three-state output buffers. It operates across –40°C to +85°C, supports 0 V–10 V / 0 V–20 V / ±5 V / ±10 V input ranges, achieves 8 µs max conversion time, and interfaces directly with 8- and 16-bit microprocessor buses. It is used in precision industrial data acquisition systems requiring calibrated, self-contained ADC functionality.

For engineers reviewing the AD774BAR datasheet, AD774BAR pinout, AD774BAR application, or AD774BAR equivalent, key selection criteria include its guaranteed ±1 LSB integral linearity over temperature, 8 µs conversion speed, SOIC-28 package compatibility with AD574A layouts, and support for both standalone and microprocessor-controlled operation modes.

Technical Context

The AD774BAR implements a SAR architecture with an internal 10.00 V ±1% trimmed reference and laser-trimmed thin-film resistors for scaling and bipolar offset. Its control logic accepts R/C, CS, CE, A0, and 12/8 inputs to configure 8-bit or 12-bit read cycles and initiate conversions in full-control or standalone mode.

It features dual-mode digital interface: 12-bit parallel outputs (DB11–DB0) configurable as one word or two bytes, with three-state buffers enabling direct bus connection. Input impedance is 5 kΩ (10 VIN) or 10 kΩ (20 VIN), and analog supply rails require ±12 V or ±15 V with +5 V logic supply.

Key Specifications

Pinout & Package

AD774BAR is housed in a 28-lead plastic SOIC (R-28) package with standard 0.3-inch body width and 0.050-inch lead pitch. Pin numbering follows industry-standard DIP/SOIC orientation (pin 1 at top-left corner, counterclockwise).

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD774BAR, AD781JRZ adds sampling capability but increases system complexity with external reference needs, while AD1674KN offers tighter linearity at lower speed and legacy through-hole assembly - making AD774BAR optimal for surface-mount, high-speed, self-contained 12-bit conversion.

Availability

AD774BAR is available at Aetrix Electronics and suitable for industrial process monitoring, test & measurement equipment, avionics sensor interfaces, and medical instrumentation requiring stable component supply across extended temperature ranges.

Supply support for AD774BAR 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 since 1965.

The AD774BAR belongs to Analog Devices' legacy high-accuracy SAR ADC product line, designed specifically for applications demanding calibrated, self-contained 12-bit conversion with minimal external components and compatibility with AD574A-based systems.

FAQ

What is the maximum conversion rate supported by the AD774BAR?

The AD774BAR achieves a maximum conversion time of 8 µs, enabling a theoretical maximum sampling rate of 125 kSPS. This assumes ideal timing margins, no bus contention, and immediate read access after STS goes low. Real-world throughput may be lower due to microprocessor interface overhead, especially in 8-bit byte-read configurations requiring two cycles per conversion.

Does the AD774BAR require external calibration components?

The AD774BAR includes laser-trimmed thin-film resistors for offset, gain, and bipolar scaling, so external calibration is not required for most applications. Factory calibration guarantees ±1 LSB integral linearity and ±2 LSB unipolar offset over –40°C to +85°C. Trim resistors (R1, R2) are provided only for system-level fine-tuning when absolute accuracy tighter than spec limits is needed.

Can the AD774BAR operate with only +5 V and ground supplies?

No. The AD774BAR requires three independent supplies: +5 V (VLOGIC), +12 V or +15 V (VCC), and –12 V or –15 V (VEE). The analog section uses bipolar rails to support ±5 V and ±10 V input ranges and maintain linearity across full-scale excursions. Operating with only +5 V and ground will prevent proper analog core function and likely cause catastrophic failure.

How does the AD774BAR handle input signals beyond its specified voltage ranges?

The AD774BAR's absolute maximum ratings allow analog inputs up to ±24 V relative to analog common (Pin 9), exceeding its normal ±10 V range. However, input current limiting resistors inside the device protect against damage - sustained overvoltage will saturate the internal comparator and produce invalid or clipped digital outputs, not destruction. For reliable operation, inputs must stay within the selected range (e.g., 0 V–10 V or ±5 V) defined by external BIP OFF and REF IN connections.

Is the AD774BAR pin-compatible with the AD574A, and what are the key functional improvements?

Yes, the AD774BAR is fully pin-compatible with the AD574A and maintains identical pin functions and package outline. Key improvements include 8 µs max conversion time (vs. 35 µs for AD574A), lower power consumption (375 mW vs. ~500 mW), integrated 10 V reference with 1% accuracy, and enhanced linearity (±1 LSB vs. ±0.5 LSB typical but unguaranteed for AD574A). These deliver faster, more accurate, and simpler system integration.