AD7821KN

Overview

The AD7821KN is an 8-bit analog-to-digital converter featuring a built-in track-and-hold function and half-flash conversion architecture. It operates from a single +5 V supply for unipolar inputs or dual ±5 V supplies for bipolar signals, with a maximum sampling rate of 1 MHz and a conversion time of 660 ns. The device provides latched three-state data outputs compatible with standard microprocessor control signals. It exhibits a total unadjusted error of ±1 LSB max over the operating temperature range of –40 °C to +85 °C. Power dissipation is typically 50 mW, and it utilizes ratiometric reference inputs without requiring an external clock.

Feature Summary

• Built-in track-and-hold capability supporting input signal frequencies up to 100 kHz
• Half-flash conversion technique eliminating the need for an external clock signal
• Flexible power supply configuration allowing operation from single +5 V or dual ±5 V sources
• Standard microprocessor interface with latched three-state data outputs and overflow pin

Applications

• Digital signal processing systems requiring precise sampling intervals
• Voice recognition and echo cancellation circuits
• Adaptive filtering applications
• High-speed data acquisition systems

Procurement Notes

Verify the specific ordering suffix KN corresponds to the Plastic DIP-20 package variant when sourcing components. Confirm that the required temperature range aligns with the commercial specification limits of –40 °C to +85 °C. Ensure that system design accounts for the ESD sensitivity warnings associated with the LC2MOS fabrication process during handling and installation procedures.

Selection Notes

Select this component when an 8-bit resolution with a 1 MHz sampling rate is required without external timing circuitry. The half-flash architecture simplifies board layout by removing clock generation needs. Consider the unipolar or bipolar input flexibility based on whether the system uses single or dual power supplies. Verify that the source impedance allows for proper settling within the specified delay times between conversions.

Part Context

The AD7821KN belongs to the AD7821 series of high-speed ADCs fabricated using Linear Compatible CMOS (LC2MOS) technology. This series offers improved performance over the AD7820, specifically regarding faster conversion times and higher signal bandwidth. The KN suffix identifies the plastic DIP-20 package option within the broader family that includes SOIC and Cerdip variants.

Replacement Considerations

The AD7820 serves as a predecessor model but features slower conversion speeds and lower bandwidth. Direct substitution requires verification that the application can tolerate the AD7820's 1.36 µs conversion time and 6.4 kHz signal bandwidth limitations compared to the AD7821's specifications.