Analog Devices Inc. AD684JQ

Overview

AD684JQ from Analog Devices is a monolithic quad sample-and-hold amplifier (SHA) with four independent, matched channels, each featuring internal hold capacitors, 1 µs acquisition time to 0.01%, 75 ps aperture jitter, and 0.01 µV/µs droop rate - designed for high-accuracy multichannel data acquisition front ends driving 12- to 14-bit ADCs.

For engineers reviewing the AD684JQ datasheet, AD684JQ pinout, AD684JQ application, or AD684JQ equivalent, this device is selected for simultaneous sampling in precision instrumentation, radar signal conditioning, and high-throughput test equipment where interchannel matching, low hold-mode drift, and fast settling are critical.

Technical Context

The AD684JQ implements a self-correcting BiMOS architecture that actively compensates for charge injection, gain error, and offset after hold command assertion - ensuring accuracy over temperature without external trimming. Its four fully independent channels share no analog signal path, enabling true parallel sampling with <300 ps interchannel aperture offset.

Each channel operates with ±12 V supplies, delivers ±5 mA output drive into low-impedance ADC inputs, and maintains 80 dB interchannel isolation at 100 kHz - supporting simultaneous hold across all four channels while minimizing crosstalk in dense mixed-signal systems.

Key Specifications

Pinout & Package

AD684JQ is housed in a 16-pin Cerdip (Q-16) package with 0.3" wide body, MIL-STD-883 compliant construction, and ceramic hermetic sealing for high-reliability industrial and defense applications.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LF398N and HA5147A, the AD684JQ provides superior integration (on-chip hold capacitors), tighter interchannel matching (<300 ps aperture offset vs. none specified), and lower droop (0.01 µV/µs), making it uniquely suited for new 12-bit+ multichannel DAQ designs requiring minimal external components and guaranteed timing correlation.

Availability

AD684JQ is available at Aetrix Electronics and suitable for radar signal conditioning, automated test equipment, and medical imaging data acquisition requiring stable component supply across extended production lifecycles.

Supply support for AD684JQ 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 AD684 product line was engineered specifically for high-fidelity, multichannel data acquisition systems demanding simultaneous sampling, low droop, and exceptional interchannel matching - targeting applications where timing coherence and DC accuracy are non-negotiable.

FAQ

What is the operating temperature range for the AD684JQ?

The AD684JQ is specified for operation from 0°C to +70°C. This commercial-grade temperature range aligns with industrial control and test equipment environments where ambient conditions remain within standard room-temperature bounds. The J-grade variant guarantees all electrical specifications - including 1 µs acquisition time and 75 ps aperture jitter - across this full range. Unlike the A-grade (–40°C to +85°C) or S-grade (–55°C to +125°C), the AD684JQ does not undergo extended temperature screening but remains fully characterized and tested per Analog Devices' production standards.

Does the AD684JQ require external hold capacitors?

No, the AD684JQ integrates precision hold capacitors on-die for all four channels, eliminating the need for external capacitors and associated layout challenges such as guarding, parasitic pickup, or capacitor matching. This monolithic integration directly contributes to its 0.01 µV/µs droop rate and ensures consistent hold performance across temperature and unit-to-unit variation. External capacitors are neither recommended nor supported in the AD684JQ's functional architecture - doing so would disrupt the calibrated self-correcting loop and degrade accuracy.

Can the AD684JQ drive ADCs directly without an output buffer?

Yes, the AD684JQ can directly drive high-speed 12-bit ADCs such as the AD7672 and AD674. Its output stage delivers ±5 mA drive current with 0.3 Ω typical output resistance, enabling it to settle to 1 mV within 500 ns after HOLD assertion - sufficient to meet the aperture requirements of these converters without added delay or buffering. However, for ADCs requiring differential inputs or higher input impedance, an external driver (e.g., AD711) may still be needed; the AD684JQ itself provides single-ended, low-impedance outputs optimized for direct connection to SAR and flash ADCs.

What is the significance of the "Q" in AD684JQ?

The "Q" suffix in AD684JQ denotes a 16-lead Cerdip (ceramic dual in-line package) with hermetic ceramic sealing and 0.3" body width. This package meets MIL-STD-883 mechanical and environmental screening requirements, providing enhanced reliability, moisture resistance, and thermal stability compared to plastic DIP variants. The Q-package is explicitly listed in the AD684 ordering guide as the only option for the J-grade device, confirming its qualification for demanding industrial and defense applications where long-term parameter stability and solder-joint integrity are critical.

How does the AD684JQ achieve low interchannel crosstalk?

The AD684JQ achieves ≤–80 dB interchannel isolation at 100 kHz through complete physical and electrical separation of its four SHA channels - including independent input/output routing, dedicated HOLD control lines, and monolithic BiMOS layout techniques that minimize substrate coupling. Unlike multiplexed or shared-amplifier architectures, each channel has its own precision amplifier, switch network, and hold capacitor, preventing signal leakage even during simultaneous sampling. This isolation is measured and guaranteed across the full 0°C to +70°C range and is integral to the device's ability to support coherent multichannel acquisition without calibration-induced errors.