AD7851AR

Overview

The AD7851AR is a high-speed, 14-bit successive approximation register (SAR) analog-to-digital converter manufactured by Analog Devices Inc. It operates from a single 5 V supply and supports throughput rates of up to 333 kSPS in the A grade and 285 kSPS in the K grade. The device features a pseudo-differential input with selectable ranges of 0 V to VREF or ±VREF/2. Key electrical specifications include a maximum integral nonlinearity of ±2 LSB for the A grade and ±1 LSB for the K grade, along with a typical power dissipation of 63 mW in normal mode. It utilizes a flexible serial interface compatible with standard microprocessor protocols.

Feature Summary

• Integrated self-calibration and system calibration capabilities with autocalibration on power-up to maintain accuracy over time and temperature variations.
• Pseudo-differential analog input architecture supporting two distinct voltage ranges for versatile signal conditioning applications.
• Flexible serial interface supporting multiple communication modes including SPI, QSPI, and 8051 compatibility.
• Low power consumption design featuring a dedicated sleep mode with minimal power draw while retaining calibration data.

Applications

• Digital Signal Processing systems requiring high-speed conversion.
• Speech recognition and synthesis hardware.
• Spectrum analysis equipment.
• DSP servo control loops.
• Instrumentation and control systems.

Procurement Notes

Verify the specific grade (A or K) and package variant when ordering, as performance metrics such as throughput rate and linearity error differ between versions. Confirm that the required operating temperature range aligns with the selected model's specifications. Ensure proper ESD precautions are observed during handling due to the sensitivity of the CMOS construction. Cross-reference the pinout and interface timing requirements with the host microcontroller design prior to integration.

Selection Notes

Select the A grade version if operation at temperatures down to -40°C is required, noting the ±2 LSB integral nonlinearity specification. Choose the K grade for commercial temperature ranges (0°C to 85°C) where tighter linearity of ±1 LSB is necessary. Consider the SOIC-24 package for surface mount assembly. Evaluate the need for external reference components versus utilizing the internal reference source based on system noise requirements and board space constraints.

Part Context

The AD7851AR belongs to the AD7851 series of serial sampling ADCs from Analog Devices. It shares functional similarities with other SAR converters but is distinguished by its integrated calibration memory and single-supply operation. The 'AR' suffix denotes the SOIC-24 package option within this product family, differentiating it from PDIP or SSOP variants which share identical electrical characteristics but differ in physical footprint and thermal properties.

Replacement Considerations

Direct replacements include AD7851KR and AD7851ARS, which offer identical electrical performance but vary in package type or temperature grade. Verify that any substitute maintains the same 24-lead SOIC footprint and serial interface timing parameters to ensure pin-to-pin compatibility without circuit redesign.