AD7856AR

Overview

The AD7856AR is an 8-channel, 14-bit successive approximation register (SAR) analog-to-digital converter operating from a single 5 V supply. It delivers a throughput rate of 285 kSPS with a typical power dissipation of 60 mW in normal mode and 2.5 µW in automatic power-down. The device features self- and system calibration, flexible serial interfaces (SPI/QSPI/8051/mP), and supports pseudo-differential or single-ended inputs. It operates within a temperature range of -40°C to +85°C and is housed in a 24-lead SOIC package.

Feature Summary

• Integrated self-calibration and system calibration capabilities ensure accuracy over time and temperature variations.
• Flexible serial interface compatible with SPI, QSPI, 8051, and microprocessor protocols for versatile digital connectivity.
• Automatic power-down after conversion significantly reduces power consumption for battery-operated applications.

Applications

• Battery-powered systems including personal digital assistants and mobile communications
• Medical instruments requiring high precision data acquisition
• Instrumentation and control systems
• High-speed modems

Procurement Notes

Verify the specific grade suffix against the required operating temperature range before ordering. The 'R' suffix denotes the SOIC package variant. Confirm that the A-grade specification meets the -40°C to +105°C requirement if applicable, as this part number typically corresponds to the commercial or industrial grade depending on the full datasheet revision. Ensure compatibility with existing 5 V logic levels.

Selection Notes

Select this component when eight channels of 14-bit resolution are required at speeds up to 285 kSPS. It is suitable for designs needing low power consumption with automatic power-down features. Verify that the input voltage range of 0 to VREF aligns with the sensor signals. Consider the available serial interface modes if interfacing with specific microcontrollers like 8051 architectures.

Part Context

The AD7856 belongs to Analog Devices' family of high-speed, low-power sampling ADCs. It shares architectural similarities with other SAR converters but distinguishes itself through its integrated multi-channel multiplexer and onboard calibration memory. The device is designed to replace discrete solutions by combining multiple functions into a single CMOS chip.

Replacement Considerations

Check for AD7856AN (DIP package) or AD7856ARS (SSOP package) for pin-compatible alternatives with different form factors. Evaluate AD7853 for single-channel requirements or AD7854 for 4-channel configurations if channel count can be reduced. Cross-reference pinouts and control registers to ensure software compatibility during substitution.