Analog Devices Inc. AD7884AQ

Overview

AD7884AQ from Analog Devices is a 16-bit monolithic sampling analog-to-digital converter with internal sample-and-hold, 5.3 µs conversion time, ±5 V or ±3 V input ranges, and 166 kSPS throughput. It uses a two-pass flash architecture, operates from ±5 V supplies with 3 V reference, and delivers 84 dB SNR - deployed in high-precision data acquisition systems for industrial control and medical instrumentation.

For engineers reviewing the AD7884AQ datasheet, AD7884AQ pinout, AD7884AQ application, or AD7884AQ equivalent, this page provides verified technical context, real-world design meaning of key specs, validated pin functions, confirmed application roles, and two rigorously cross-checked alternative parts for ±5 V/±3 V high-speed 16-bit ADC selection.

Technical Context

The AD7884AQ implements a two-pass flash conversion architecture: first pass digitizes the 9 MSBs using a 9-bit ADC and 16-bit DAC feedback; second pass resolves the residue error to generate the full 16-bit result. Conversion is initiated asynchronously via CONVST, with BUSY signaling active-low during conversion.

It supports dual analog input ranges (±5 V and ±3 V) via dedicated force/sense pins (±5VINF/±5VINS, ±3VINF/±3VINS), requires external 3 V reference (VREF+S/VREF+F), and features separate analog/digital grounds (AGNDS/AGNDF, DGND) and power rails (AVDD/AVSS, VDD/VSS) to maintain dc accuracy and dynamic performance.

Key Specifications

Pinout & Package

AD7884AQ is housed in a 40-lead CERDIP package (Q-40), hermetically sealed for high-reliability industrial and military environments. Pin layout follows standard CERDIP numbering with Pin 1 identifier in top-left corner (viewed from top).

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7884AQ, AD7884BQ offers verified linearity assurance at identical speed and packaging, while AD7892BP trades parallel interface and dual-range capability for smaller footprint and faster conversion - making AD7884AQ optimal for legacy microprocessor buses requiring ±3 V/±5 V adaptability.

Availability

AD7884AQ is available at Aetrix Electronics and suitable for industrial process monitoring, medical patient monitoring, and automated test equipment requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for AD7884AQ 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 Norwood, MA.

The AD7884AQ belongs to Analog Devices' precision high-speed ADC product line, engineered for applications demanding 16-bit resolution, sub-µs conversion, and robust operation in harsh industrial and medical environments.

FAQ

What is the maximum sampling rate supported by the AD7884AQ?

The AD7884AQ achieves a maximum throughput rate of 166 kSPS. This is enabled by overlapping acquisition and conversion phases - while the second pass resolves the residue from one sample, the input SHA acquires the next. The 5.3 µs conversion time and 2.5 µs acquisition time are both specified at TMIN to TMAX (–40°C to +85°C), ensuring consistent performance across its full operating range. AD7884AQ maintains this rate without external clocking due to its internal oscillator.

Does the AD7884AQ require an external clock signal?

No, the AD7884AQ does not require an external clock signal. It contains an internal oscillator that precisely controls the timing of both conversion passes and BUSY assertion. This eliminates clock routing complexity and jitter sensitivity, simplifying system design. All timing parameters - including t2 (CONVST to BUSY delay), t6 (data access time), and t7 (bus relinquish time) - are guaranteed with the internal oscillator active, as documented in the REV. E timing tables.

Can the AD7884AQ operate with a single +5 V supply?

No, the AD7884AQ requires dual ±5 V analog supplies (AVDD = +5 V, AVSS = –5 V) and dual ±5 V digital supplies (VDD = +5 V, VSS = –5 V). Its architecture depends on symmetric rail operation for the sample-and-hold, residue amplifier, and internal DAC. Attempting single-supply operation violates Absolute Maximum Ratings and will cause functional failure. Decoupling must use separate 10 µF tantalum + 0.1 µF ceramic per AVDD/AVSS, and 1 µF ceramic per VDD/VSS.

What is the purpose of the AGNDS and AGNDF pins on the AD7884AQ?

AGNDS (analog ground sense) and AGNDF (analog ground force) form a Kelvin connection for the 9-bit ADC and residue amplifier ground return. They must be driven by a low-offset, low-noise op amp (e.g., AD817) configured as a unity-gain buffer - not tied directly together or to system ground. Doing so degrades INL, bipolar zero error, and gain accuracy. The AD7884AQ datasheet explicitly states that direct connection causes measurable dc specification degradation, though ac performance (SNR, THD) remains largely unaffected.

How does the AD7884AQ handle ±3 V versus ±5 V input ranges?

The AD7884AQ selects input range via hardware pin configuration: for ±5 V, ±5VINF is driven and ±5VINS returned to AGND (±3V pins tied to AGND); for ±3 V, ±3VINF is driven and ±3VINS returned to AGND (±5V pins tied to AGND). Internal resistor networks (R1–R8) and op-amp A1 condition the signal to 0 V to –3 V for the 9-bit ADC. The selected range directly sets full-scale range (10 V or 6 V) and LSB size (152.6 µV or 91.5 µV), with no software or register configuration required.