Analog Devices Inc. AD7871TQ

Overview

AD7871TQ from Analog Devices is a complete monolithic 14-bit successive approximation analog-to-digital converter (ADC) with integrated track-and-hold amplifier, 3 V buried Zener reference, and laser-trimmed internal clock. It delivers 83 kSPS throughput, 80 dB SNR at 10 kHz, 57 ns data access time, and operates from ±5 V supplies with ±3 V bipolar analog input range. It is used in high-speed DSP servo control and spectrum analysis systems requiring stable dc accuracy and dynamic performance.

For engineers reviewing the AD7871TQ datasheet, AD7871TQ pinout, AD7871TQ application, or AD7871TQ equivalent, this page provides verified technical context, real-world interface configurations (parallel/byte/serial), confirmed timing constraints (t6 = 70 ns max data access), thermal operating limits (−55°C to +125°C), and validated alternative options for signal acquisition designs.

Technical Context

The AD7871TQ implements a self-contained SAR architecture with on-chip 3 V temperature-compensated Zener reference and internal 2 MHz oscillator-no external timing components required. Its track-and-hold acquires signals to 14-bit accuracy in ≤2 μs, enabling full-scale conversion of 41.5 kHz sine waves while maintaining 80 dB SNR.

It supports three configurable output modes via the 14/8/CLK pin: 14-bit parallel (DB0–DB13), two 8-bit bytes (HBEN-controlled), or 14-bit serial (SSTRB/SCLK/SDATA). Logic interfaces comply with TTL levels (VINH ≥ 2.4 V, VINL ≤ 0.8 V), and BUSY/INT provides asynchronous conversion status signaling.

Key Specifications

Pinout & Package

AD7871TQ is housed in a 28-pin CERDIP package (hermetically sealed ceramic dual in-line) with 0.600-inch body width and 0.100-inch lead pitch. Pin 24 is NC; all digital I/O pins are three-state controlled by CS and RD; AGND and DGND are separate for analog/digital noise isolation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 14-bit sampling ADC applications.

Compared with AD7872TQ, AD7871TQ offers flexible parallel/serial interface and larger package for easier probing; compared with ADS8320U, it trades 2-bit resolution for full integration, lower power, and bipolar input readiness-making it superior for ruggedized, space-constrained, ±5 V embedded systems.

Availability

AD7871TQ is available at Aetrix Electronics and suitable for digital signal processing, high-speed modems, and spectrum analysis applications requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for AD7871TQ 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 semiconductor leader specializing in high-performance analog, mixed-signal, and digital signal processing technologies for precision measurement and control.

The AD7871TQ belongs to the AD7871/AD7872 family of complete sampling ADCs designed for applications demanding integrated timing, reference, and interface logic in harsh environments-from aerospace telemetry to industrial automation.

FAQ

What is the maximum analog input frequency supported by the AD7871TQ?

The AD7871TQ can accurately convert full-power sine wave inputs up to 41.5 kHz while maintaining specified dynamic performance, including 77 dB SNR. This limit arises from the combination of 83 kSPS throughput and the track-and-hold amplifier's 500 kHz 0.1 dB bandwidth-ensuring faithful digitization without aliasing or slew-induced distortion in the AD7871TQ signal path.

Does the AD7871TQ require external clock components?

No, the AD7871TQ features a self-contained, laser-trimmed internal 2 MHz clock oscillator. Tying the CLK pin (5) to VSS enables this internal timing source, eliminating need for crystals, oscillators, or RC networks. External clocks are optional and accepted via the CLK pin when system-level synchronization is required-making the AD7871TQ truly complete with no external timing dependencies.

How does the 14/8/CLK pin configure data output formats on the AD7871TQ?

The 14/8/CLK pin (28) selects among three AD7871TQ output modes: +5 V enables 14-bit parallel only (DB0–DB13); 0 V enables both byte-mode (HBEN-controlled DB0–DB7) and serial mode (SSTRB/SCLK/SDATA) with gated SCLK; −5 V enables same dual-mode output but with continuous SCLK. This single pin determines interface topology without firmware changes-critical for hardware-flexible system design.

What is the purpose of the CREF pin on the AD7871TQ?

The CREF pin (23) is the dedicated decoupling node for the AD7871TQ's internal 3 V buried Zener reference. A 10 nF capacitor must be placed between CREF and AGND to minimize reference noise and ensure stable DAC operation. This external capacitor is mandatory-not optional-as its absence degrades SNR and increases integral nonlinearity beyond datasheet limits in the AD7871TQ.

Can the AD7871TQ operate with unipolar input signals?

Yes, the AD7871TQ supports unipolar operation using its internal REFOUT (25) to bias the analog input stage. By applying REFOUT to an external summing amplifier (e.g., Figure 14), the input range shifts from ±3 V to 0 V–6 V or scaled ranges like 0 V–5 V. The output remains twos-complement but can be converted to straight binary by inverting the MSB-enabling seamless integration into unipolar control loops without external level shifters in the AD7871TQ signal chain.