Analog Devices Inc. AD7680ARM

Overview

AD7680ARM from Analog Devices is a 16-bit, successive approximation analog-to-digital converter (ADC) in a 6-lead SOT-23 package, operating from a single 2.5 V to 5.5 V supply with 100 kSPS throughput, 86 dB SNR at 10 kHz, and 3 mW typical power dissipation at 2.5 V - deployed in battery-powered medical instruments and portable data acquisition systems.

For engineers reviewing the AD7680ARM datasheet, AD7680ARM pinout, AD7680ARM application, or AD7680ARM equivalent, key selection considerations include unipolar 0 V to VDD input range, SPI/QSPI/μWire/DSP-compatible serial interface, no pipeline delay, 8 μs max conversion time, and standby current of 0.5 μA - all critical for low-power, space-constrained embedded sensing designs.

Technical Context

The AD7680ARM implements a capacitive DAC-based successive approximation architecture with integrated track-and-hold, sampling on the falling edge of CS and initiating conversion simultaneously. Its reference is derived directly from VDD, eliminating external reference components and enabling full-scale input range from 0 V to VDD.

Conversion timing is fully synchronous to the external SCLK (up to 2.5 MHz), requiring 20–24 clock cycles per 16-bit result, with no latency or pipeline delay. Power management is controlled via CS assertion and deassertion, supporting dynamic power-down between conversions to achieve sub-microwatt quiescent consumption.

Key Specifications

Pinout & Package

AD7680ARM is housed in a 6-lead SOT-23 package (JEDEC MO-178AA), measuring 2.9 mm × 1.6 mm × 1.1 mm, optimized for high-density PCB layouts in portable electronics.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7683ARMZ and ADS8320EB/250, the AD7680ARM uniquely combines true unipolar simplicity, SOT-23 miniaturization, and VDD-referenced operation - making it optimal for new space- and power-constrained designs where analog input is naturally referenced to the system supply.

Availability

AD7680ARM is available at Aetrix Electronics and suitable for battery-powered medical instruments, portable data loggers, optical sensor modules, and industrial control loop feedback systems requiring stable component supply across long production lifecycles.

Supply support for AD7680ARM 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, with R&D and manufacturing operations spanning 15 countries.

The AD7680ARM belongs to Analog Devices' PulSAR® family of precision SAR ADCs, designed specifically for low-power, high-resolution data acquisition in portable and energy-sensitive applications - emphasizing integration, ease of use, and supply-referenced flexibility.

FAQ

What is the maximum recommended source impedance for the AD7680ARM analog input?

The AD7680ARM analog input should be driven from a source impedance ≤100 Ω to maintain specified THD and SNR performance. At higher impedances (e.g., 1 kΩ), THD degrades significantly - Figure 8 in the datasheet shows >10 dB THD increase at 10 kHz with 1 kΩ source. For high-impedance sensors, an op amp buffer (e.g., AD8605) is required before the AD7680ARM input.

Does the AD7680ARM require an external voltage reference?

No, the AD7680ARM does not require an external voltage reference. Its reference is internally derived from the VDD supply, establishing a 0 V to VDD unipolar input range. This eliminates external reference components and associated layout complexity, though VDD must be well-decoupled (0.1 μF ceramic + 10 μF tantalum) to preserve accuracy and noise performance.

Can the AD7680ARM operate with a 3.3 V microcontroller SPI interface?

Yes, the AD7680ARM supports 3.3 V logic compatibility. Its digital inputs (CS, SCLK) accept voltages up to 7 V, and its SDATA output swings from 0 V to VDD - so with VDD = 3.3 V, SDATA outputs standard 3.3 V logic levels. No level-shifting circuitry is needed when interfacing with 3.3 V MCUs such as STM32L4 or nRF52840.

What is the minimum SCLK frequency required for reliable operation of the AD7680ARM?

The AD7680ARM specifies a minimum SCLK frequency of 250 kHz (Table 4). Below this, timing margins for t5 (SCLK low pulse width) and t6 (SCLK high pulse width) may be violated, risking incomplete data transfers or metastability. For robust operation, use ≥500 kHz - especially in noisy environments where clock edge integrity may be compromised.

How does the AD7680ARM handle power supply sequencing during startup?

The AD7680ARM tolerates asynchronous application of digital inputs (CS, SCLK) prior to VDD due to its ±0.3 V absolute maximum rating on digital pins - unlike analog inputs, which must remain within −0.3 V to VDD + 0.3 V. This eliminates strict power sequencing requirements, simplifying system-level power-up design and avoiding latch-up risk during brown-out conditions.