Analog Devices Inc. AD7661ASTZ

Overview

AD7661ASTZ from Analog Devices is a 16-bit, 100 kSPS unipolar charge redistribution SAR analog-to-digital converter with integrated 2.5 V reference, ±2.5 LSB INL, and 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 AD7661ASTZ datasheet, AD7661ASTZ pinout, AD7661ASTZ application, or AD7661ASTZ equivalent, this page provides verified technical context, real-world interface timing constraints, confirmed package mapping to 48-lead LQFP, and validated alternative options for high-accuracy DC/AC signal digitization requiring low drift and no missing codes.

Technical Context

The AD7661ASTZ implements a factory-calibrated charge redistribution SAR architecture with internal error correction circuitry, eliminating pipeline delay and enabling immediate data availability post-conversion. Its dual-mode digital interface supports both 16-bit parallel readout and 2-wire serial operation compatible with 3 V or 5 V logic levels.

It integrates a trimmed 2.5 V reference with ±3 ppm/°C typical drift and includes dedicated pins (PDREF, PDBUF, REFBUFIN) for flexible internal/external reference selection and buffering. The analog input accepts 0 V to 2.5 V unipolar signals with 68 dB CMRR at 10 kHz and 820 kHz –3 dB bandwidth.

Key Specifications

Pinout & Package

AD7661ASTZ is housed in a 48-lead LQFP (ST-48) package with exposed pad, rated for –40°C to +85°C operation. Pin 1 identifier is marked on top surface; AGND, DGND, and OGND are separately routed for analog/digital isolation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7661ASTZ, AD7660ASTZ trades throughput and linearity for lower cost in static measurement systems, while AD7664ASTZ extends performance at the expense of power and interface compatibility - making AD7661ASTZ the optimal balance for 100 kSPS precision acquisition with minimal design overhead.

Availability

AD7661ASTZ is available at Aetrix Electronics and suitable for medical instrumentation, spectrum analysis, and process control monitoring requiring stable component supply, long-term calibration integrity, and industrial temperature operation.

Supply support for AD7661ASTZ 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, with R&D and manufacturing infrastructure spanning North America, Europe, and Asia.

The AD7661ASTZ belongs to Analog Devices' PulSAR® family of precision SAR ADCs, designed specifically for high-resolution, low-latency data acquisition in instrumentation, medical, and industrial control systems where DC accuracy and AC fidelity are equally critical.

FAQ

What is the maximum sampling rate supported by the AD7661ASTZ?

The AD7661ASTZ supports a maximum throughput rate of 100 kSPS, corresponding to a minimum conversion cycle time of 10 µs. This is achievable in both parallel and serial interface modes, with BUSY going LOW within 1.25 µs after CNVST falling edge. At this rate, the device consumes 16 mW without internal reference enabled and 40 mW with reference active. The AD7661ASTZ maintains full 16-bit no-missing-code performance across its entire specified temperature range.

Does the AD7661ASTZ require an external reference voltage?

No, the AD7661ASTZ includes a factory-trimmed 2.5 V internal reference with ±3 ppm/°C typical temperature drift and ±15 ppm/°C maximum drift over –40°C to +85°C. The PDREF pin controls reference enable/disable: driving PDREF LOW activates the internal reference, while driving it HIGH disables it and allows use of an external reference applied to REFBUFIN. The internal reference eliminates the need for external reference ICs in most precision applications unless tighter drift or different voltage levels are required.

How does the AD7661ASTZ handle digital interface selection between parallel and serial modes?

The AD7661ASTZ uses the SER/PAR pin to select interface mode: logic LOW configures the device for 16-bit parallel operation (D[0:15], RD, CS), while logic HIGH enables serial mode using SDOUT, SCLK, and SYNC pins. In serial mode, additional configuration pins (EXT/INT, INVSYNC, INVSCLK, RDC/SDIN) define clock source, sync polarity, and data format. This dual-interface capability allows one hardware design to support both high-speed parallel reads and space-efficient serial communication without redesigning the PCB layout.

What is the purpose of the TEMP pin on the AD7661ASTZ?

Pin 45 (TEMP) on the AD7661ASTZ provides an analog voltage output proportional to die temperature: 300 mV at 25°C with 1 mV/°C sensitivity. This output is buffered and calibrated, enabling direct connection to an external ADC or monitoring circuit for system-level thermal management. It supports cold-junction compensation in thermocouple interfaces and aids in drift compensation modeling - especially valuable in applications where ambient temperature variations affect analog signal chain accuracy.

Can the AD7661ASTZ operate from a single 5 V supply?

Yes, the AD7661ASTZ operates from a single 5 V supply applied to AVDD and DVDD (4.75 V to 5.25 V), with OVDD supporting 2.7 V to 5.25 V for interface logic level compatibility. All analog, digital, and I/O power domains are internally regulated and isolated via dedicated ground pins (AGND, DGND, OGND). This single-supply operation simplifies power design in embedded systems and eliminates the need for negative rails or multiple regulators - a key advantage over older bipolar-supply ADC architectures.