Analog Devices Inc. AD7666ACP

Overview

AD7666ACP from Analog Devices is a 16-bit, 500 kSPS charge redistribution SAR analog-to-digital converter with integrated 2.5 V reference, ±2.0 LSB INL, and dual parallel/serial (SPI/QSPI/MICROWIRE/DSP-compatible) interface. It operates from a single 5 V supply, delivers 88 dB S/(N+D) at 20 kHz, and targets precision data acquisition in medical instruments and spectrum analysis systems.

For engineers reviewing the AD7666ACP datasheet, AD7666ACP pinout, AD7666ACP application, or AD7666ACP equivalent, this page provides verified technical context, real-world interface timing constraints, thermal drift behavior of its internal reference, and validated alternative ADCs for unipolar 16-bit sampling at ≤500 kSPS.

Technical Context

The AD7666ACP implements a hardware-calibrated charge redistribution SAR architecture with no pipeline delay, enabling immediate data availability post-conversion. Its internal error correction circuitry ensures monotonicity and guarantees no missing 16-bit codes across –40°C to +85°C.

It supports both parallel (16-bit bus) and serial (master/slave SPI-compatible) modes via SER/PAR control, with configurable clocking (internal/external SCLK), frame sync (SYNC), and data format (straight binary/twos complement via OB/2C). Reference operation is selectable between internal 2.5 V (±15 ppm/°C max drift) and external sources using PDREF/PDBUF pins.

Key Specifications

Pinout & Package

The AD7666ACP is available in a 48-lead LQFP package (ST-48 footprint) with exposed pad for thermal management. Pin functions are fully defined for both parallel and serial operation modes, including dedicated reference, temperature sensing, and power domain separation (AVDD/DVDD/OVDD).

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7666ACP, AD7664BCPZ trades speed and integrated reference for lower cost and power in slower systems, while ADS8860IDRCT offers higher throughput and modern low-voltage compatibility at the expense of parallel interface flexibility and industrial temperature range.

Availability

AD7666ACP is available at Aetrix Electronics and suitable for medical instrumentation, spectrum analysis, data acquisition systems, and battery-powered test equipment requiring stable component supply across industrial temperature ranges.

Supply support for AD7666ACP 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 is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, headquartered in Norwood, MA.

The AD7666ACP belongs to the PulSAR® family of precision SAR ADCs designed for applications demanding high resolution, excellent ac/dc accuracy, and flexible digital interfacing without pipeline latency.

FAQ

What is the maximum operating temperature range for the AD7666ACP?

The AD7666ACP is specified for operation from –40°C to +85°C. This industrial temperature range is guaranteed for all electrical parameters including INL (±2.0 LSB), S/(N+D) (88 dB), and reference drift (±15 ppm/°C). The device uses a thermally enhanced 48-lead LQFP package with exposed pad to maintain junction temperature within safe limits under full-load conditions. Extended temperature versions are not offered for the AD7666ACP.

Does the AD7666ACP require an external reference, or can it operate with its internal reference?

AD7666ACP can operate with either its internal 2.5 V reference or an external reference. When PDREF is driven LOW, the internal reference is enabled and provides 2.493 V to 2.507 V at 25°C with ±15 ppm/°C max drift. To use an external reference, PDREF must be held HIGH and a 2.3 V to (AVDD – 1.85 V) source applied to REFBUFIN. The internal buffer (enabled via PDBUF LOW) may be used with either reference source to improve drive capability.

How does the AD7666ACP handle simultaneous parallel and serial interface access?

The AD7666ACP does not support simultaneous parallel and serial interface access. Interface mode is selected exclusively by the SER/PAR pin: LOW configures the 16-bit parallel bus (D[0:15]), while HIGH reassigns D[7:11] to serial functions (SDOUT/SCLK/SYNC/RDERROR). Attempting concurrent access causes undefined behavior. Bus arbitration must be handled externally, and mode switching requires resetting the device via the RESET pin to ensure proper state initialization.

What is the significance of the BYTESWAP pin on the AD7666ACP?

The BYTESWAP pin on AD7666ACP controls byte ordering of the 16-bit parallel output. When BYTESWAP is LOW, D[7:0] carries the LSB byte and D[15:8] carries the MSB byte - standard little-endian alignment. When HIGH, byte order is swapped: D[7:0] outputs the MSB byte and D[15:8] outputs the LSB byte. This feature simplifies firmware integration with microcontrollers that expect specific byte alignment without requiring software bit manipulation, reducing CPU overhead in high-throughput acquisition systems.

Can the AD7666ACP's temperature sensor output be used for system-level thermal compensation?

Yes, the AD7666ACP's TEMP pin provides a calibrated analog voltage output (300 mV at 25°C, ±10 mV tolerance) with 1 mV/°C sensitivity, enabling direct system-level thermal compensation. Its output impedance is 4 kΩ, so a high-impedance ADC input or op-amp buffer is recommended for accurate reading. Used alongside the device's known thermal drift characteristics (e.g., ±1.4 ppm/°C full-scale error drift), the TEMP output allows real-time correction of gain/offset errors in precision measurement applications without adding discrete sensors.