Analog Devices Inc. AD7851AR

Overview

AD7851AR from Analog Devices is a 14-bit, 333 kSPS serial analog-to-digital converter (ADC) with pseudo-differential input, on-chip 4.096 V reference, and self/system calibration capability. It operates from a single 5 V supply, delivers ±2 LSB integral nonlinearity at –40°C to +85°C, and supports dual input ranges (0 V to VREF and ±VREF/2). It is used in high-speed DSP servo control and spectrum analysis systems requiring stable DC accuracy and low power.

For engineers reviewing the AD7851AR datasheet, AD7851AR pinout, AD7851AR application, or AD7851AR equivalent, this page provides verified technical context, calibrated performance data, package-specific pin functions, real-world use scenarios, and validated alternative options for industrial signal acquisition designs.

Technical Context

The AD7851AR implements a successive approximation register (SAR) architecture with integrated track-and-hold, charge redistribution DAC, and comparator. Its analog front-end supports pseudo-differential sampling with acquisition time of 0.33 µs and full-power bandwidth of 20 MHz.

It features a flexible serial interface supporting five modes-including SPI/QSPI/8051-compatible and self-clocking variants-and includes dedicated calibration registers for offset and gain adjustment. Calibration is initiated via the CAL pin and executed under internal controller supervision with guaranteed completion times dependent on master clock frequency.

Key Specifications

Pinout & Package

AD7851AR is housed in a 24-lead SOIC (R-24) package with 0.3-inch body width and standard JEDEC MS-013AC footprint. Pin assignments are identical across PDIP, SOIC, and SSOP variants per Analog Devices' ordering guide.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-speed SAR ADC applications.

Compared with AD7851KR and ADS8325IPW, the AD7851AR uniquely balances 14-bit resolution, 333 kSPS throughput, integrated reference, and single-supply operation-making it optimal for industrial DSP and real-time control where speed, accuracy, and integration are jointly constrained.

Availability

AD7851AR is available at Aetrix Electronics and suitable for DSP servo control, spectrum analysis, and instrumentation and control systems requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for AD7851AR 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, with design centers worldwide.

The AD7851AR belongs to Analog Devices' precision high-speed SAR ADC product line, engineered for demanding industrial and communications applications requiring fast, accurate, and calibrated analog-to-digital conversion with minimal external components.

FAQ

What is the maximum sample rate supported by the AD7851AR?

The AD7851AR supports a maximum throughput rate of 333 kSPS at –40°C to +85°C when operated with a 7 MHz master clock (CLKIN). This corresponds to a conversion time of 2.78 µs and requires proper timing alignment of CONVST, BUSY, and serial interface signals per Interface Mode 2 or 3 specifications. The AD7851AR maintains guaranteed performance within datasheet limits across its full rated temperature range.

Does the AD7851AR include an internal voltage reference?

Yes, the AD7851AR integrates a factory-trimmed 4.096 V reference accessible at the REFIN/REFOUT pin. It exhibits typical temperature coefficient of 50 ppm/°C and supports external override from 4 V to AVDD. The internal reference eliminates need for external reference ICs in most applications, and the AD7851AR's CREF1 and CREF2 pins accommodate required external capacitors for DAC charge redistribution stability.

How does the AD7851AR handle calibration?

The AD7851AR supports both self-calibration (internal DAC and reference) and system calibration (external signal path) via dedicated CAL pin and on-chip calibration registers. Full self-calibration takes ~41.7 ms at 6 MHz CLKIN and adjusts offset and gain errors; calibration data is retained in nonvolatile memory during SLEEP mode. The AD7851AR also allows manual read/write access to calibration registers for field recalibration without hardware reset.

What serial interface protocols does the AD7851AR support?

The AD7851AR supports five configurable serial interface modes: Mode 1 (2-wire 8051), Mode 2 (3-wire SPI/QSPI), Mode 3 (QSPI with inverted SYNC), and Modes 4–5 (self-clocking output modes). Configuration is controlled by SM1, SM2, and POLARITY pins. All modes use DIN/DOUT/SCLK/SYNC signals and are software-compatible with common microcontrollers including 8XC51, ADSP-21xx, and TMS320Cxx families.

What is the analog input structure of the AD7851AR?

The AD7851AR features a pseudo-differential analog input with AIN(+) and AIN(–) terminals. It supports two selectable input ranges via the AMODE pin: unipolar (0 V to VREF) and bipolar (±VREF/2 centered at VREF/2). Input voltage must remain between AGND and AVDD at all times; leakage current is ±1 µA max and input capacitance is 20 pF typical. This architecture enables noise rejection while accommodating both ground-referenced and floating sensor sources.