Analog Devices Inc. AD7872KNZ

Overview

AD7872KNZ 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 serial-only digital interface. It operates from ±5 V supplies, accepts bipolar ±3 V analog inputs, delivers 83 kSPS throughput, achieves 80 dB SNR at 10 kHz, and features 57 ns data access time - enabling high-fidelity digitization in DSP servo control and spectrum analysis systems.

For engineers reviewing the AD7872KNZ datasheet, AD7872KNZ pinout, AD7872KNZ application, or AD7872KNZ equivalent, this page provides verified technical context, validated pin functions, confirmed dynamic and DC specifications, real-world use scenarios, and two rigorously cross-checked alternative parts for serial-output 14-bit sampling ADCs requiring ±3 V input range and internal reference.

Technical Context

The AD7872KNZ implements a self-contained LC2MOS SAR architecture with laser-trimmed internal 2 MHz clock, eliminating external timing components. Its track-and-hold acquires to 14-bit accuracy in ≤2 μs, and conversion completes in ≤11 μs using the internal clock.

All signal paths - analog input, reference, and serial output - are internally referenced to AGND and DGND, with strict separation maintained via dedicated VDD, VSS, AGND, and DGND pins. Serial data transmission uses open-drain SDATA and SCLK outputs with defined pull-up requirements (4.7 kΩ on SDATA/SSTRB, 2 kΩ on SCLK) and framing via active-low SSTRB.

Key Specifications

Pinout & Package

AD7872KNZ is housed in a 16-pin plastic DIP (PDIP) package with 0.3-inch body width and through-hole mounting. Pin spacing follows standard 0.1-inch grid; pin 1 marked by notch or dot.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7872KNZ, AD7870KNZ trades 2 bits of resolution and 8 dB SNR for lower cost and power, while ADS8320UB delivers higher resolution at the expense of increased design complexity, external component count, and loss of integrated bipolar input capability.

Availability

AD7872KNZ is available at Aetrix Electronics and suitable for digital signal processing, high-speed modems, spectrum analysis, and DSP servo control applications requiring stable component supply, long-term obsolescence management, and traceable sourcing.

Supply support for AD7872KNZ 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 AD787x family was designed specifically for high-fidelity, medium-speed data acquisition in DSP-centric systems - emphasizing integrated references, low-noise analog cores, and flexible digital interfaces without external timing components.

FAQ

What is the absolute maximum input voltage for AD7872KNZ?

The absolute maximum analog input voltage for AD7872KNZ is VSS − 0.3 V to VDD + 0.3 V, which corresponds to −5.3 V to +5.3 V under nominal ±5 V supply conditions. However, the specified linear input range remains ±3 V; exceeding this range risks clipping or nonmonotonic behavior even if within absolute limits. Always limit VIN to ±3 V for guaranteed 14-bit performance in AD7872KNZ applications.

Does AD7872KNZ require external clock circuitry?

No, AD7872KNZ does not require external clock circuitry. It integrates a laser-trimmed 2 MHz internal oscillator activated by tying the CLK pin to VSS. This eliminates crystals, RC networks, or external clock generators. An external TTL-compatible clock may be applied to CLK only if system synchronization is needed - but the internal clock is fully sufficient for standalone 83 kSPS operation in AD7872KNZ.

How is the reference voltage used internally in AD7872KNZ?

In AD7872KNZ, the internal 3 V buried Zener reference serves dual roles: it sets the full-scale range for the 14-bit SAR DAC and provides the dc bias for bipolar input operation. The REFOUT pin makes this reference available externally, but loading it beyond 500 µA or adding >50 pF capacitance degrades ADC accuracy and stability. For optimal performance, AD7872KNZ relies entirely on its internal reference without external dependencies.

What are the critical layout requirements for AD7872KNZ?

AD7872KNZ requires strict analog/digital ground separation: AGND and DGND must be connected at a single point near the device, with separate copper pours. A 10 nF capacitor must be placed between CREF and AGND, and 0.1 µF ceramics must decouple VDD and VSS to their respective grounds. VIN and REFOUT traces must avoid digital routing; SDATA, SCLK, and SSTRB require controlled-impedance routing with their specified pull-up resistors placed adjacent to the AD7872KNZ pins.

Can AD7872KNZ operate with unipolar input signals?

Yes, AD7872KNZ can operate with unipolar inputs using an external offset circuit - typically applying the REFOUT voltage to shift a 0–3 V input range into the device's native ±3 V window. Figure 14 in the AD7872KNZ datasheet shows a verified unipolar configuration using resistive scaling and REFOUT as the offset source. The output remains twos-complement and must be converted to straight binary by inverting the MSB for unipolar interpretation.