SN74LS85D

Overview

The SN74LS85D is a 4-bit magnitude comparator manufactured by onsemi, belonging to the Low Power Schottky (LS) logic family. It compares two 4-bit binary or BCD numbers and provides three active-high outputs indicating whether Input A is greater than, less than, or equal to Input B. The device features cascading inputs to allow expansion for comparing numbers with more than four bits. Packaged in a 16-pin Small Outline Integrated Circuit (SOIC), it operates within standard TTL voltage ranges and supports high-speed switching with low power dissipation typical of LS technology.

Feature Summary

• Performs 4-bit magnitude comparison between two binary or BCD inputs
• Provides distinct outputs for greater-than, less-than, and equal-to conditions
• Includes cascading inputs for multi-bit expansion capabilities

Applications

• Digital arithmetic logic units requiring subtraction or comparison operations
• Address decoding systems in microprocessor-based designs
• Control logic for determining sequence order in automated processes

Procurement Notes

Verify the manufacturer marking on the component body, as Texas Instruments also produces this part number. Confirm the 'D' suffix indicates the SOIC-16 package variant. Check RoHS compliance status via official datasheets, as legacy LS parts may vary by production batch. Ensure the source document explicitly lists onsemi as the manufacturer to avoid confusion with TI equivalents.

Selection Notes

Select this component when designing circuits requiring precise 4-bit magnitude comparison with low power consumption. The LS family offers a balance of speed and power suitable for general-purpose digital logic. Consider the SOIC package for surface-mount assembly requirements. Verify that the system voltage aligns with standard TTL levels and that cascading inputs are utilized if comparisons exceed four bits.

Part Context

This component is part of the widely adopted 74xx series of digital logic ICs. The SN74LS85 specifically implements the magnitude comparator function within the Low Power Schottky subset, known for improved performance over standard TTL while maintaining compatibility. It serves as a fundamental building block in digital electronics for decision-making logic based on numerical values.

Replacement Considerations

The SN74LS85N (DIP package) and SN74LS85NSR (tape and reel) are direct functional equivalents from Texas Instruments. Other manufacturers may offer pin-compatible alternatives such as the MC74LS85. Verify electrical characteristics and package dimensions before substitution.