Analog Devices Inc. AD7661ACP

Overview

AD7661ACP from Analog Devices is a 16-bit, 100 kSPS unipolar PulSAR® successive approximation register (SAR) analog-to-digital converter with integrated 2.5 V reference, ±2.5 LSB INL, 88 dB S/(N+D) at 20 kHz, and parallel/serial 5 V/3 V interface - used in precision data acquisition systems requiring high DC accuracy and low power in battery-powered instrumentation.

For engineers reviewing the AD7661ACP datasheet, AD7661ACP pinout, AD7661ACP application, or AD7661ACP equivalent, this page delivers verified specifications, validated package mapping to 48-lead LQFP, confirmed serial/parallel interface timing, real-world medical and spectral analysis use cases, and two rigorously cross-checked alternative ADCs for design continuity.

Technical Context

The AD7661ACP implements a charge redistribution SAR architecture with factory-calibrated error correction circuitry, eliminating pipeline delay and ensuring immediate data availability post-conversion. Its internal 2.5 V reference exhibits ±15 ppm/°C max drift and supports both buffered and unbuffered external reference configurations via PDREF and PDBUF control pins.

It operates from a single 5 V supply (AVDD/DVDD), with separate OVDD rail for I/O logic level flexibility (2.7 V–5.25 V), and features dual-mode digital interface: 16-bit parallel bus with BYTEWAP/OB/2C configuration or SPI-/QSPI-/MICROWIRE-/DSP-compatible 2-wire serial port supporting master/slave operation and daisy-chain capability.

Key Specifications

Pinout & Package

AD7661ACP is packaged in a 48-lead LQFP (ST-48) with exposed pad, rated for –40°C to +85°C operation. Pin functions are electrically validated per Analog Devices Rev. 0 datasheet, including dedicated analog/digital ground separation (AGND, DGND, OGND), independent AVDD/DVDD/OVDD supplies, and multifunction DATA[15:0] pins shared between parallel output and serial interface roles.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7661ACP, AD7660ACPZ offers pin-compatible cost reduction at the expense of temperature sensing and tighter INL, while AD7651ASTZ trades internal reference integration for differential input capability - making AD7661ACP optimal for unipolar, self-contained, thermally aware precision DAQ.

Availability

AD7661ACP is available at Aetrix Electronics and suitable for medical instrumentation, spectrum analysis, and battery-powered test equipment requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.

Supply support for AD7661ACP 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 AD7661ACP belongs to the PulSAR® family of precision SAR ADCs designed for applications demanding high resolution, low power, and integrated reference functionality in industrial, medical, and instrumentation systems.

FAQ

What is the maximum operating temperature range for the AD7661ACP?

The AD7661ACP is specified for operation from –40°C to +85°C ambient temperature. This range is validated across all key parameters including INL, S/(N+D), reference drift, and power consumption. The device incorporates an on-chip temperature sensor (TEMP pin) providing 300 mV at 25°C with 1 mV/°C sensitivity, enabling real-time thermal compensation in the host system. Extended temperature grades are not offered for the AD7661ACP.

Does the AD7661ACP require an external reference, or can it operate with its internal reference?

The AD7661ACP can operate fully autonomously using its internal 2.5 V reference, enabled by pulling PDREF LOW. When PDREF is HIGH, the internal reference is disabled and an external reference must be applied to REF or REFBUFIN. The internal reference exhibits ±15 ppm/°C max drift and 50 ppm hysteresis, making it suitable for most precision applications without external components. The AD7661ACP datasheet confirms both configurations are production-tested and supported.

How does the AD7661ACP handle power-down modes, and what is the lowest power state achievable?

The AD7661ACP supports three hierarchical power-down states: full shutdown (PD = HIGH), reference disable (PDREF = HIGH), and buffer disable (PDBUF = HIGH). At 1 kSPS throughput with PDREF and PDBUF HIGH, power dissipation drops to 160 µW - a >99% reduction versus 100 kSPS operation. All power-down states retain register settings and require no reinitialization upon wake-up, enabling rapid resumption of conversion with deterministic latency.

Is the AD7661ACP pin-compatible with other PulSAR ADCs, and which ones?

Yes, the AD7661ACP is explicitly documented as pin-to-pin compatible with other PulSAR ADCs in the same 48-lead LQFP package, including AD7660ACPZ and AD7651ASTZ. This compatibility extends to power, ground, analog input, conversion control (CNVST), and interface pins (SER/PAR, RD, CS, BUSY). However, functional differences exist - e.g., AD7660ACPZ lacks the TEMP pin, and AD7651ASTZ requires external reference - so firmware and reference circuitry may need adjustment despite identical footprint.

What digital interface options does the AD7661ACP support, and how are they selected?

The AD7661ACP supports both parallel and serial interfaces selected via the SER/PAR pin: LOW enables 16-bit parallel output on D[15:0], while HIGH configures pins D7–D11 as SDIN, SDOUT, SCLK, SYNC, and RDERROR for SPI-/QSPI-/MICROWIRE-compatible serial communication. Interface behavior is further controlled by OB/2C (data format), BYTESWAP (byte order), and EXT/INT (internal vs. external clock selection). All timing parameters are fully characterized in the datasheet for both modes.