AD7858AR

Overview

The AD7858AR is an 8-channel, 12-bit successive approximation register (SAR) analog-to-digital converter (ADC) manufactured by Analog Devices Inc. It operates from a single 3 V to 5.5 V supply and supports a throughput rate of 200 kSPS. The device features eight single-ended or four pseudo-differential analog inputs with a range of 0 V to VREF. It includes system and self-calibration capabilities, automatic power-down after conversion, and a flexible serial interface compatible with SPI, QSPI, and 8051 protocols. The part is housed in a 24-lead SOIC package.

Feature Summary

• Integrated system and self-calibration with autocalibration on power-up for long-term accuracy.
• Flexible serial interface supporting multiple microprocessor protocols including SPI and QSPI.
• Automatic power-down mode activated after each conversion cycle to minimize energy consumption.
• Configurable input multiplexer allowing selection between eight single-ended or four pseudo-differential channels.

Applications

• Battery-powered systems such as personal digital assistants and mobile communications devices.
• Medical instruments requiring low-power data acquisition.
• Pen computers and portable instrumentation.
• Industrial control systems and high-speed modems.

Procurement Notes

Verify the specific revision level and temperature grade when sourcing components, as specifications may vary between A and B grades. Confirm that the supplier provides original manufacturer documentation to ensure authenticity. Check for moisture sensitivity levels and storage conditions prior to installation. Ensure compatibility with existing board layouts regarding the 24-lead SOIC footprint and pin definitions.

Selection Notes

Select the AD7858AR when a higher sampling rate of 200 kSPS is required compared to the lower-power AD7858L variant. Consider the power dissipation characteristics, which are typically 20 mW at 3.6 V, against application thermal constraints. Evaluate the need for external versus internal reference configurations based on required linearity performance. Ensure the serial interface timing requirements align with the host microcontroller's clock speeds.

Part Context

The AD7858AR belongs to the AD7858 family of high-speed, low-power ADCs from Analog Devices. It is designed for applications demanding moderate resolution and speed within a compact form factor. The component utilizes CMOS construction to achieve low power dissipation while maintaining 12-bit accuracy. It serves as a bridge between analog sensor signals and digital processing systems in portable and industrial environments.

Replacement Considerations

The AD7858BRZ is listed as a parameter-equivalent replacement offering improved linearity error specifications. Verify pinout compatibility and electrical parameter alignment before substitution. Ensure that any alternative component meets the same voltage and temperature operating ranges.