74F521SJ

Overview

The Fairchild Semiconductor 74F521SJ is an expandable 8-bit identity comparator housed in a 20-lead Small Outline Package (SOP). It compares two 8-bit words and outputs a LOW signal when the inputs are identical. The device features active pull-up and pull-down circuits for high-speed operation. It operates within a supply voltage range of 4.5V to 5.5V, with a typical propagation delay of 13ns at 5V. The component supports cascading for expanded comparison capabilities.

Feature Summary

• Performs 8-bit identity comparison between two parallel input words
• Provides active pull-up and pull-down output drivers for fast switching
• Supports expansion through dedicated cascade inputs and outputs

Applications

• Digital data comparison systems
• Address decoding logic
• Equality checking in microprocessor interfaces

Procurement Notes

Verify the package marking matches the 20-lead SOP specification. Confirm the manufacturer origin as Fairchild Semiconductor or authorized successor entities like onsemi. Ensure the datasheet revision aligns with the required electrical characteristics. Check for RoHS compliance status if environmental regulations apply to the final assembly.

Selection Notes

Select this component when an 8-bit magnitude comparison is required in a surface-mount design. The 74F521SJ offers faster performance than standard 74LS series devices. Consider the 20-pin footprint constraints during PCB layout. Verify that the 5V logic levels match the system voltage requirements.

Part Context

This part belongs to the 74F (Fast) logic family, known for improved speed over earlier TTL standards. The 74F521 specifically addresses the need for parallel data equality detection. It replaces older discrete comparator solutions with a single integrated circuit solution.

Replacement Considerations

The 74F521PC is a DIP equivalent. The 74F521N is another variant. Verify pin compatibility before substitution.