Analog Devices Inc. AD7661ASTZRL

Overview

AD7661ASTZRL from Analog Devices is a 16-bit, 100 kSPS unipolar successive approximation register (SAR) analog-to-digital converter with integrated 2.5 V reference, ±2.5 LSB INL, and parallel/serial interface. It operates from a single 5 V supply, delivers 88 dB SNR at 20 kHz, and targets precision data acquisition in medical instruments and battery-powered instrumentation.

For engineers reviewing the AD7661ASTZRL datasheet, AD7661ASTZRL pinout, AD7661ASTZRL application, or AD7661ASTZRL equivalent, this page provides verified technical context, real-world interface timing constraints, confirmed package mapping to 48-lead LQFP, and validated alternative options for signal chain design continuity.

Technical Context

The AD7661ASTZRL implements a charge redistribution SAR architecture with factory-calibrated error correction, eliminating pipeline delay and ensuring immediate data availability post-conversion. Its internal 2.5 V reference exhibits ±3 ppm/°C typical drift and supports both buffered and unbuffered external reference configurations via PDREF and PDBUF control pins.

It supports dual-mode digital interfacing: 16-bit parallel bus with BYTEWAP and OB/2C format control, and SPI/QSPI/MICROWIRE-compatible serial mode with programmable clock division (DIVSCLK[1:0]), active-low/high SYNC polarity (INVSYNC), and SCLK edge inversion (INVSCLK) - all operating across 3 V or 5 V logic levels.

Key Specifications

Pinout & Package

AD7661ASTZRL is housed in a 48-lead LQFP (ST-48) package with exposed pad, rated for –40°C to +85°C operation. Pin functions are electrically validated per Analog Devices Rev. 0 datasheet.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7661ASTZRL, AD7660ASTZ trades temperature sensing and linearity for lower unit cost, while AD7651ASTZ sacrifices integration and ease-of-use for speed and differential input flexibility - making AD7661ASTZRL optimal for compact, self-contained, high-linearity unipolar measurement nodes.

Availability

AD7661ASTZRL is available at Aetrix Electronics and suitable for medical instrumentation, portable test equipment, and industrial data acquisition systems requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.

Supply support for AD7661ASTZRL 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 AD7661 belongs to the PulSAR® family of precision SAR ADCs designed for applications demanding high resolution, low noise, and integrated reference stability - especially where board space, power, and calibration complexity are constrained.

FAQ

What is the maximum sampling rate supported by the AD7661ASTZRL?

The AD7661ASTZRL supports a maximum throughput rate of 100 kSPS, corresponding to a minimum conversion cycle time of 10 µs. This is achievable under specified conditions: AVDD = DVDD = 5 V, OVDD ≥ 2.7 V, and proper decoupling. At this rate, the AD7661ASTZRL maintains its full AC performance including 88 dB S/(N+D) and ±2.5 LSB INL.

Does the AD7661ASTZRL require an external reference voltage?

No, the AD7661ASTZRL includes a factory-trimmed 2.5 V internal reference with ±3 ppm/°C typical drift. External reference use is optional and enabled by driving PDREF HIGH; when using the internal reference, PDREF must be held LOW. The AD7661ASTZRL also supports external reference inputs via REFBUFIN with internal buffering controlled by PDBUF.

Can the AD7661ASTZRL operate with a 3 V digital interface voltage?

Yes, the AD7661ASTZRL supports 3 V logic levels through its OVDD supply pin, which accepts 2.7 V to 5.25 V. When OVDD = 3 V, all digital outputs (D[15:0], BUSY, SYNC, SDOUT) are compatible with 3 V microcontrollers or FPGAs, and digital inputs (RD, CS, CNVST) recognize 2.0 V as VIH minimum - enabling seamless integration into mixed-voltage systems without level shifters.

What is the function of the BYTESWAP pin on the AD7661ASTZRL?

The BYTESWAP pin on the AD7661ASTZRL controls byte ordering in parallel interface mode. When LOW, D[7:0] carries the LSB byte and D[15:8] carries the MSB byte; when HIGH, D[7:0] carries the MSB byte and D[15:8] carries the LSB byte. This allows alignment with host processor endianness requirements without software bit manipulation, reducing CPU overhead in real-time data acquisition.

How does the AD7661ASTZRL handle power-down mode?

The AD7661ASTZRL enters low-power state when the PD pin is driven HIGH, reducing current draw to <1 µA (typical). In this mode, conversions are inhibited after completion of the current cycle, and internal circuits (including reference buffer if enabled) are disabled. Recovery to full operation requires ~5 ms for reference turn-on settling if PDREF was previously HIGH - a timing parameter explicitly specified in the AD7661ASTZRL datasheet.