Analog Devices Inc. AD7851KR

Overview

AD7851KR from Analog Devices is a 14-bit, 285 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, features ±1 LSB integral nonlinearity (K grade), and supports unipolar (0 V to VREF) and bipolar (±VREF/2) input ranges for precision data acquisition in industrial control and DSP systems.

For engineers reviewing the AD7851KR datasheet, AD7851KR pinout, AD7851KR application, or AD7851KR equivalent, this page delivers verified specifications, real-world timing behavior, calibrated accuracy at 85°C, power-down modes (5 µW typ), and SPI/QSPI/8051-compatible serial interface configuration - all confirmed for the SOIC-packaged K-grade variant.

Technical Context

The AD7851KR implements a successive approximation register (SAR) architecture with integrated track-and-hold, charge redistribution DAC, and comparator. Its conversion cycle requires 19.5 master clock cycles (t_CONVERT ≤ 3.25 µs at 6 MHz CLKIN), and it supports five configurable serial interface modes including self-clocking outputs.

Calibration is performed via dedicated CAL pin and internal registers: automatic on power-up, user-initiated self-calibration (41.7 ms typ), and system offset/gain calibration (4.63 ms / 37.04 ms typ). Input ranges are selected by AMODE pin, and reference flexibility allows external 4–5 V sources or internal 4.096 V REFOUT.

Key Specifications

Pinout & Package

AD7851KR is housed in a 24-lead SOIC package (R-24 footprint, 0.3 inch width) with standard JEDEC MS-013AC dimensions and gull-wing leads. Thermal impedance is θ_JA = 75°C/W.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7851ARZ-REEL3, AD7851KR trades 1 LSB INL and 48 kSPS throughput for lower cost and qualification at 0°C–85°C; versus ADS8325IPW, it offers faster sampling, built-in reference, and calibration - at the expense of resolution and SPI-only simplicity.

Availability

AD7851KR is available at Aetrix Electronics and suitable for industrial process monitoring, DSP servo control, automotive engine control units, and high-speed data acquisition systems requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for AD7851KR 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 AD7851 family was designed for high-speed, precision data acquisition in demanding industrial and automotive environments where calibration stability, single-supply operation, and flexible serial interfacing are critical.

FAQ

What is the maximum sampling rate of the AD7851KR?

The AD7851KR achieves a maximum throughput rate of 285 kSPS at 0°C to +85°C with a 6 MHz master clock. At elevated temperatures up to +125°C, its guaranteed rate drops to 238 kSPS using a 5 MHz clock. This performance is validated per the K-grade specification in the official AD7851 datasheet Rev. B, and applies to both unipolar and bipolar input configurations when using the internal 4.096 V reference.

Does the AD7851KR include an internal voltage reference?

Yes, the AD7851KR integrates a factory-trimmed 4.096 V bandgap reference accessible at the REFIN/REFOUT pin. It can operate as a reference output or accept an external 4–5 V source. The internal reference exhibits 50 ppm/°C temperature coefficient and supports full 14-bit accuracy when used with proper CREF1 (0.1 µF) and CREF2 (0.01 µF) decoupling capacitors, as specified in the AD7851KR datasheet.

How does the AMODE pin affect the AD7851KR's input configuration?

The AMODE pin selects between two analog input ranges: logic low configures unipolar mode (0 V to VREF), where AIN(+) must remain ≥ AIN(–); logic high enables bipolar mode (±VREF/2), where AIN(–) is biased to VREF/2 and AIN(+) may swing below it - but never below AGND. This selection also determines output coding: natural binary for unipolar, two's complement for bipolar. Both modes are supported simultaneously in hardware.

Can the AD7851KR perform self-calibration without external components?

Yes, the AD7851KR executes complete self-calibration (offset and gain) autonomously upon power-up or via a rising edge on the CAL pin, requiring no external circuitry. The process takes 41.7 ms typical at 6 MHz CLKIN and stores correction values in on-chip registers. System calibration - which corrects external front-end errors - also runs internally but requires user-provided reference conditions during execution.

What serial interface protocols does the AD7851KR support?

The AD7851KR supports five configurable serial modes: Mode 1 (2-wire 8051), Mode 2/3 (3-wire SPI/QSPI), and Modes 4/5 (self-clocking with SCLK output). All use DIN/DOUT/SCLK/SYNC pins and are selected via control register bits. POLARITY pin determines SCLK edge sensitivity. No external protocol translator is needed - direct connection to ADSP-21xx, TMS320C2x, or 8XC51 microcontrollers is documented in the AD7851KR datasheet.