74F521SC 8-Bit Identity Comparator Equivalent & Substitute Parts

Part Overview

The 74F521SC is an 8-bit magnitude comparator with active low output manufactured by onsemi. This logic component performs identity comparison operations, outputting an active low A=B signal. The part is currently classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement.

Substiute Parts

74F521SC

onsemiIn Stock: 143674F521SC Datasheet

Current PartRFQ

SN74F521DW

Texas InstrumentsIn Stock: 2702SN74F521DW Datasheet

DirectRFQ

SN74F521DWR

Texas InstrumentsIn Stock: 3943SN74F521DWR Datasheet

DirectRFQ

SN74F521NSR

Texas InstrumentsIn Stock: 2992SN74F521NSR Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitute parts for the 74F521SC are qualified based on the following critical parameters that determine functional and mechanical compatibility:

Electrical Parameters (Must Match):

• 8-bit identity comparator function
• Active low A=B output
• 4.5V ~ 5.5V supply voltage range
• 1mA / 20mA output current specifications
• 10ns maximum propagation delay @ 5V, 50pF load
• 0°C ~ 70°C operating temperature range

Mechanical Parameters (Must Match or Be Compatible):

• 20-SOIC or 20-SO package footprint
• Surface mount mounting type

Substitution Categories:

Direct Substitutes (Identical Electrical & Mechanical):

• SN74F521DW (Texas Instruments) – 20-SOIC package, Last Time Buy status
• SN74F521DWR (Texas Instruments) – 20-SOIC package, Active status

Similar Substitute (Identical Electrical, Alternate Package Variant):

• SN74F521NSR (Texas Instruments) – 20-SO package (0.209", 5.30mm Width), Active status

All substitute parts maintain the 74F series logic family designation and identical functional specifications.

Parameter Comparison

Engineering Selection Recommendations

For New Designs and Long-Term Availability: SN74F521DWR is the recommended primary substitute. This part carries Active product status from Texas Instruments, ensuring continued availability and supply chain stability. It maintains identical electrical specifications and 20-SOIC package dimensions to the 74F521SC, enabling direct PCB footprint compatibility without layout modifications.

For Existing Inventory Management: SN74F521DW provides an intermediate option with Last Time Buy status, suitable for transitional procurement phases. This part is electrically and mechanically identical to SN74F521DWR but with limited future availability.

For Package-Constrained Applications: SN74F521NSR offers Active status with identical electrical performance but in a 20-SO package variant with reduced width (0.209" vs. 0.295"). This part is applicable only if PCB layout accommodates the narrower package footprint.

All substitute parts are ROHS3 compliant, meeting modern environmental and regulatory requirements. The 74F series logic family designation is maintained across all substitutes, ensuring compatibility with existing 74F logic system designs.

Frequently Asked Questions (FAQ)

Q: Can SN74F521DWR directly replace 74F521SC without PCB modifications? A: Yes. SN74F521DWR is electrically and mechanically identical, with matching 20-SOIC package dimensions (0.295", 7.50mm width). Direct footprint substitution is possible without layout changes.

Q: What is the difference between SN74F521DW and SN74F521DWR? A: Both parts are electrically and mechanically identical with matching 20-SOIC packages. The primary difference is product status: SN74F521DW is Last Time Buy, while SN74F521DWR is Active. For new designs, SN74F521DWR is preferred for long-term availability.

Q: Can SN74F521NSR be used as a substitute if space is limited? A: SN74F521NSR maintains identical electrical specifications but uses a narrower 20-SO package (0.209" width vs. 0.295"). Substitution is possible only if the PCB layout is designed to accommodate the reduced package width. Pin configuration and electrical performance remain compatible.

Q: Are all substitute parts RoHS compliant? A: Yes. SN74F521DW, SN74F521DWR, and SN74F521NSR are all ROHS3 compliant, meeting current environmental regulations.

Q: What is the supply voltage tolerance for these comparators? A: All parts operate within 4.5V to 5.5V supply range. This specification is identical across the 74F521SC and all substitute parts.

Q: Do these parts have identical propagation delay characteristics? A: Yes. All parts specify 10ns maximum propagation delay at 5V with 50pF load, ensuring timing-critical applications maintain consistent performance across substitutions.