Analog Devices Inc. AD684AQ

Overview

AD684AQ from Analog Devices is a monolithic quad sample-and-hold amplifier (SHA) designed for high-speed, multichannel data acquisition front ends. It delivers 1 µs acquisition time to 0.01%, 75 ps aperture jitter, and 0.01 µV/µs droop rate across its four independent channels, each with internal hold capacitors and ±5 V input range - enabling direct interfacing with 12- to 14-bit ADCs like AD7672 in industrial instrumentation.

For engineers reviewing the AD684AQ datasheet, AD684AQ pinout, AD684AQ application, or AD684AQ equivalent, key selection criteria include interchannel matching (≤300 ps aperture offset), hold-mode accuracy (±3 mV offset), temperature-stable operation (–40°C to +85°C), low-noise performance (125 µV rms hold mode noise), and MIL-STD-883-compliant Cerdip packaging for rugged environments.

Technical Context

The AD684AQ implements a self-correcting BiMOS architecture that actively compensates for charge injection, gain error, and offset drift after hold command assertion - ensuring accurate held output despite inaccurate track-mode behavior. Its four fully independent SHA channels share no analog signal path, achieving ≥80 dB interchannel isolation at 100 kHz.

Each channel features matched small-signal bandwidth (4 MHz), full-power bandwidth (1 MHz), and output drive capability (±5 mA), with dc-coupled single-ended I/O referenced to common. The device operates from ±10.8 V to ±13.2 V supplies and integrates on-chip hold capacitors - eliminating external components required for hold function.

Key Specifications

Pinout & Package

AD684AQ is housed in a 16-pin Cerdip (Q-16) package with 0.3" wide body, compliant with MIL-STD-883 screening for extended temperature and reliability requirements.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar quad sample-and-hold amplifier applications.

Compared with AD781JN and LF398N, the AD684AQ provides monolithic quad integration, sub-microsecond acquisition, and guaranteed interchannel matching - reducing system-level calibration burden and enabling true simultaneous sampling in high-fidelity data acquisition.

Availability

AD684AQ is available at Aetrix Electronics and suitable for industrial data acquisition, avionics signal conditioning, medical imaging front ends, and test & measurement systems requiring stable component supply across extended temperature ranges.

Supply support for AD684AQ 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 precision instrumentation, communications, and industrial markets since 1965.

The AD684AQ belongs to Analog Devices' precision data acquisition IC family, engineered specifically for multichannel, high-speed sampling applications demanding tight interchannel matching, low droop, and robust operation in harsh environments.

FAQ

What is the operating temperature range specified for the AD684AQ?

The AD684AQ is rated for operation from –40°C to +85°C. This extended industrial temperature range is validated per the device's datasheet specifications and ensures stable performance in uncontrolled environments such as factory floors or outdoor instrumentation enclosures. All electrical parameters - including acquisition time, droop rate, and interchannel offset - are guaranteed across this full range. The AD684AQ achieves this via BiMOS process optimization and on-die thermal compensation within its self-correcting architecture.

Does the AD684AQ require external hold capacitors?

No, the AD684AQ does not require external hold capacitors. It integrates precision on-chip hold capacitors for all four channels, eliminating layout sensitivity, parasitic effects, and calibration overhead associated with discrete capacitors. This monolithic integration is confirmed in the Functional Description and PRODUCT DESCRIPTION sections of the datasheet, and enables guaranteed 0.01 µV/µs droop rate and 500 ns hold settling without user intervention. External capacitors would disrupt the calibrated internal timing and degrade aperture jitter performance.

How does the AD684AQ achieve its low aperture jitter of 75 ps?

The AD684AQ achieves 75 ps maximum aperture jitter through proprietary BiMOS circuit design that minimizes switch timing variance and analog path delay mismatch. Its self-correcting architecture isolates jitter-sensitive elements from control logic, and the monolithic quad layout ensures matched propagation delays across all four channels. This value is measured and guaranteed per the AD684–SPECIFICATIONS table under "Aperture Jitter" for the A grade, and directly enables high-fidelity sampling of signals up to 10 MHz without significant SNR degradation.

Can the AD684AQ drive ADCs directly without an output buffer?

Yes, the AD684AQ can drive high-speed 12- to 14-bit ADCs directly without an output buffer. Its output resistance is specified at 0.5 Ω (dc), and it sources/sinks ±5 mA while maintaining hold-mode accuracy within 2.5 mV. This capability is explicitly validated in the PRODUCT HIGHLIGHTS section, which cites compatibility with AD578, AD674, AD7572, and AD7672 converters. The low output impedance and fast 500 ns hold settling eliminate the need for additional op-amp buffering in most designs, reducing component count and signal path error.

What is the significance of the "Q" suffix in AD684AQ?

The "Q" suffix in AD684AQ denotes a 16-pin Cerdip (ceramic dual in-line package) construction, as defined in the PACKAGE OPTIONS and ORDERING GUIDE sections of the datasheet. This hermetically sealed ceramic package provides superior moisture resistance, thermal stability, and mechanical ruggedness compared to plastic DIP variants - making it suitable for military, aerospace, and industrial applications requiring long-term reliability under thermal cycling and vibration. The Q-16 footprint is standardized and compatible with MIL-STD-883 screening processes.