Analog Devices Inc. AD7651ASTZ

Overview

AD7651ASTZ from Analog Devices is a 16-bit, 100 kSPS PulSAR® charge redistribution SAR analog-to-digital converter operating from a single 5 V supply. It features an internal 2.5 V reference (±7 ppm/°C drift), 0 V to 2.5 V unipolar input range, no pipeline delay, and dual parallel/serial (SPI/QSPI/MICROWIRE/DSP-compatible) interface - deployed in precision data acquisition systems requiring high DC accuracy and low power at medium speed.

For engineers reviewing the AD7651ASTZ datasheet, AD7651ASTZ pinout, AD7651ASTZ application, or AD7651ASTZ equivalent, this page delivers verified technical context, real-world interface timing constraints, confirmed package mapping to 48-lead LQFP, and validated alternative options for instrumentation-grade ADC selection.

Technical Context

The AD7651ASTZ implements a capacitor-based charge redistribution SAR architecture with on-chip calibration logic and internal conversion clock generation. Its analog front-end includes a track-and-hold with 8.75 µs acquisition time, 2 ns aperture delay, and 5 ps rms aperture jitter - enabling accurate sampling of signals up to 800 kHz bandwidth without external hold circuitry.

Digital interface flexibility is achieved via SER/PAR-selectable operation: parallel mode supports 16-bit straight-binary or twos-complement output with BYTEWAP control, while serial mode offers master/slave configurations with programmable SCLK division (DIVSCLK[1:0]), SYNC polarity (INVSYNC), and clock inversion (INVSCLK) - all compatible with 3 V or 5 V host logic levels.

Key Specifications

Pinout & Package

AD7651ASTZ is packaged in a 48-lead LQFP (ST-48) with exposed pad, rated for –40°C to +85°C operation. Pin 1 identifier located at top-left corner; AGND pins (1, 36, 41, 42) and DGND pins (20, 30) provide separate analog/digital ground routing paths.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7651ASTZ, AD7652ASTZ trades internal reference for higher speed, while AD7661ASTZ retains full functional equivalence in a smaller LFCSP package - both require no firmware changes but differ in thermal performance and board space use.

Availability

AD7651ASTZ is available at Aetrix Electronics and suitable for data acquisition, medical instrumentation, digital signal processing front-ends, and process control loop monitoring requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.

Supply support for AD7651ASTZ 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 AD7651ASTZ belongs to the PulSAR® family of precision SAR ADCs designed for applications demanding high DC accuracy, low power, and flexible digital interfacing - especially where pipeline latency is unacceptable.

FAQ

What is the maximum input frequency supported by the AD7651ASTZ?

The AD7651ASTZ has a –3 dB input bandwidth of 800 kHz, meaning it can accurately digitize signals up to that frequency. For optimal AC performance (e.g., 86 dB SNR), Analog Devices specifies testing at 45 kHz with a 0.5 dB below full-scale sine wave. Higher-frequency inputs may suffer aliasing or reduced dynamic range unless properly anti-aliased; the 100 kSPS sampling rate enforces a Nyquist limit of 50 kHz for baseband signals.

Does the AD7651ASTZ require an external reference voltage?

No - the AD7651ASTZ includes a factory-trimmed internal 2.5 V reference with ±7 ppm/°C temperature drift. When PDREF is held LOW, the internal reference is active and drives the REF pin. An external reference can be used by pulling PDREF HIGH and applying 2.3 V to AVDD – 1.85 V to REFBUFIN, but doing so disables the internal reference and requires external buffering if driving multiple devices.

How does the SER/PAR pin affect the AD7651ASTZ's pin functionality?

When SER/PAR is LOW, AD7651ASTZ operates in parallel mode: D0–D15 function as a 16-bit bidirectional data bus, with RD/CS controlling read strobes. When SER/PAR is HIGH, the device enters serial mode: D8 becomes SDOUT, D9 becomes SCLK, D10 becomes SYNC, and D11 becomes RDERROR - repurposing those pins for SPI-compatible communication while retaining D0–D7 for configuration (e.g., DIVSCLK, INVSYNC).

What is the purpose of the TEMP pin on the AD7651ASTZ?

The TEMP pin on the AD7651ASTZ outputs a calibrated analog voltage proportional to die temperature: 300 mV at 25°C with 1 mV/°C slope. This allows system-level thermal monitoring without adding discrete sensors. The output has 4.3 kΩ source impedance and is intended for connection to a separate ADC or comparator - it is not used internally for reference or conversion calibration.

Can the AD7651ASTZ operate from a 3 V supply?

No - the AD7651ASTZ requires AVDD and DVDD at 4.75–5.25 V for specified performance. However, its OVDD (I/O interface supply) accepts 2.7–5.25 V, enabling direct connection to 3 V microcontrollers or FPGAs. The digital interface (RD, CS, SER/PAR, etc.) is fully compatible with 3 V logic levels when OVDD = 3 V, while core analog and digital circuitry remain powered from 5 V.