Analog Devices Inc. AD7686CRMZ

Summary of AD7686CRMZ 16-bit SAR ADC's main functions

The AD7686CRMZ from Analog Devices Inc. is a member of the PulSAR® series, representing a high-performance, 16-bit successive approximation register (SAR) analog-to-digital converter (ADC). Housed in a compact 10-lead MSOP package, the AD7686CRMZ is tailored for applications requiring accurate signal conversion—such as battery-powered systems, medical instrumentation, and process control. It achieves 16-bit resolution with no missing codes, operates from a single 5 V supply, and offers a flexible pseudo-differential input range. Its compatibility with multiple logic voltages (1.8 V up to 5 V on the digital I/O supply) and a high throughput rate of 500 kSPS make it well-suited for modern multi-channel data acquisition systems.

Main attributes and technical details of AD7686CRMZ

The AD7686CRMZ ADC stands out with a robust combination of resolution, speed, and power efficiency. It offers 16-bit resolution, typical integral nonlinearity (INL) of ±0.6 LSB (maximum ±2 LSB), and a maximum throughput of 500 kSPS, enabling the acquisition of complex analog signals with high fidelity. Its typical signal-to-noise-and-distortion (SINAD) ratio reaches 92.5 dB and total harmonic distortion (THD) is -110 dB at 20 kHz, defining its excellent dynamic performance for demanding measurement environments.

Operating on a single 5 V analog supply (with 4.5 V to 5.5 V tolerance) and a flexible digital I/O supply from 1.8 V to 5 V, the AD7686CRMZ ensures compatibility with a broad range of system controllers. Its external reference input can be as high as the supply voltage, allowing system designers to choose reference circuits that match their accuracy and stability requirements.

Power consumption is a key attribute: it consumes only 3.75 µW at 100 samples per second, 3.75 mW at 100 kSPS, and up to 21.5 mW at the maximum 500 kSPS rate. In standby mode, current draw falls to a mere 1 nA, making the AD7686CRMZ ideal for low-power, always-on embedded scenarios.

AD7686CRMZ pin layout and signal definitions

The 10-lead MSOP and LFCSP packages of the AD7686CRMZ feature a user-friendly pinout for seamless PCB integration. Key connections include:

REF: Reference voltage input (0.5 V to VDD)

IN+ and IN-: Pseudo-differential analog inputs, supporting a 0 V to VREF range

VDD: Main analog supply (5 V nominal)

VIO: Digital I/O supply (1.8 V to 5 V)

GND: System ground

CNV: Conversion-start and interface selection input

SDO: Serial data output (conversion results)

SCK: Serial clock input

SDI: Serial data input/interface mode select

The exposed pad on the package underside should be connected to ground for thermal management, although this is not mandatory for meeting electrical specifications.

Operating principle and functional diagram of AD7686CRMZ

At its heart, the AD7686CRMZ employs a charge-redistribution SAR architecture with an integrated track-and-hold circuit. The design boasts a short 2.5 ns aperture delay and ensures no pipeline delay, so conversion results are available immediately at the end of a conversion cycle. On each rising edge of CNV, the device samples the input voltage (IN+ referenced to IN-), using the provided external reference to set the input range.

A versatile, SPI-compatible serial interface is incorporated, supporting both three-wire and four-wire operation, with optional busy indication and daisy-chain functionality. System architects can thus chain multiple AD7686CRMZ devices for synchronized multi-channel data acquisition on a single bus, increasing channel density without additional pins.

With power dissipation scaling linearly with throughput, and the ability to drive digital logic operating anywhere from 1.8 V to 5 V, the AD7686CRMZ is easily adaptable to evolving embedded and remote data acquisition settings.

AD7686CRMZ electrical parameters and timing data

The AD7686CRMZ delivers outstanding performance across its entire rated temperature range (-40°C to +85°C). Key electrical parameters include:

Input common-mode rejection ratio (CMRR): 65 dB at 200 kHz

Typical gain error: ±2 LSB (max ±8 LSB), with minimal temperature drift (±0.3 ppm/°C)

Offset error: ±1.6 mV (max)

Input impedance: defined by the analog input structure, supporting high bandwidth (–3 dB bandwidth of 9 MHz)

Digital interface timing supports conversion times as fast as 1.6 µs and acquisition intervals as low as 400 ns, suitable for fast-scan acquisition modes. Multiple SCK timing modes allow tight integration with standard microcontrollers, DSPs, and FPGAs.

Use cases and applications for AD7686CRMZ

The AD7686CRMZ’s high resolution, low power operation, and robust digital interface make it optimal for diverse precision signal capture environments:

Battery-powered equipment, such as wireless sensor modules or handheld instrumentation, where power efficiency is in balance with high-accuracy needs

Medical instruments, particularly data acquisition for patient monitoring or diagnostic imaging, demanding 16-bit true resolution and low noise floor

Process control and industrial automation, enabling precise monitoring of analog signals in control loops, remote I/O, and PLCs

General-purpose instrumentation, such as high-channel count or scalable modular DAQ systems, integrating multiple ADCs in daisy-chain configurations to minimize wiring complexity

Design guidelines and integration tips for AD7686CRMZ

Successful deployment of the AD7686CRMZ involves several key engineering considerations. The external reference input (REF) must be carefully decoupled and chosen for low drift and noise to preserve true 16-bit performance. The pseudo-differential input configuration requires precise layout and grounding to minimize common-mode interference and guarantee CMRR figures.

Layout guidance includes minimizing stray capacitance on analog inputs, optimizing reference and supply decoupling, and appropriately connecting the exposed pad for thermal relief. For high-speed sampling, robust digital layout practices are also recommended to guard against crosstalk and ground bounce, especially when daisy-chaining multiple converters.

Possible alternative or substitute models for AD7686CRMZ

Engineers seeking alternatives to the AD7686CRMZ within Analog Devices’ PulSAR® family have several pin-compatible or functionally similar options:

AD7684: 16-bit, lower throughput SAR ADC in the same package, suited when 100 kSPS is sufficient

AD7687, AD7688: True differential 16-bit SAR ADCs for applications requiring fully differential measurement capability

AD7980: 16-bit, 1 MSPS SAR ADC with similar footprint and interface

AD7693: 16-bit, true differential input for improved common-mode noise rejection

For systems requiring higher resolution on the same interface and package style, devices such as the AD7691 (18-bit) can be evaluated.

Conclusion

: AD7686CRMZ value proposition in system design

The AD7686CRMZ offers an optimal blend of resolution, speed, and power consumption in a compact, system-friendly package, solidifying its role as a go-to 16-bit SAR ADC for precision data acquisition tasks. Its robust analog and digital performance, flexible supply and interface options, and straightforward migration path within the PulSAR® family make it a preferred choice for selection engineers and procurement professionals targeting scalable high-accuracy analog front-ends in space- and power-constrained designs.