74HC688N Equivalent & Substitute Parts

Part Overview

The 74HC688N is an 8-bit identity comparator manufactured by NXP USA Inc., designed for magnitude comparison applications with active low output. This device is classified as obsolete, which necessitates identification of functionally equivalent alternatives for ongoing design requirements and component sourcing.

Substiute Parts

74HC688N,652

NXP USA Inc.In Stock: 85874HC688N,652 Datasheet

Current PartRFQ

CD74HC688E

Harris CorporationIn Stock: 1869CD74HC688E Datasheet

UpgradeRFQ

SN74HC688N

Texas InstrumentsIn Stock: 7729SN74HC688N Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the 74HC688N is determined by the following critical parameters:

• 8-bit identity comparator function with A=B output
• Active low output configuration
• 20-DIP through-hole package (0.300", 7.62mm)
• Supply voltage range: 2V ~ 6V
• Output current capability: 5.2mA minimum
• Quiescent current: 8 µA maximum
• Operating temperature range compatibility

The identified substitute parts maintain functional equivalence across these core parameters while differing in manufacturer origin, product status, and compliance certifications.

Parameter Comparison

Engineering Selection Recommendations

For applications requiring the 74HC688N, the SN74HC688N manufactured by Texas Instruments is the primary substitute. This part maintains full functional equivalence across all critical electrical parameters, operates within compatible temperature ranges for standard industrial applications, and carries active product status with ROHS3 compliance certification.

The CD74HC688E from Harris Corporation provides functional equivalence but carries obsolete product status and RoHS non-compliance, limiting its suitability for new designs subject to environmental regulations.

The propagation delay specification of the SN74HC688N (36ns at 6V, 50pF) is marginally higher than the original 74HC688N (29ns), which may require timing verification in delay-sensitive applications. The operating temperature range of the SN74HC688N (-40°C ~ 85°C) is narrower than the original specification (-40°C ~ 125°C), necessitating thermal environment assessment for high-temperature applications.

Frequently Asked Questions (FAQ)

Q: Can the SN74HC688N directly replace the 74HC688N in existing designs?

A: Yes, the SN74HC688N is a direct functional replacement. Both devices share identical 20-DIP package geometry, pin configuration, supply voltage range, output current specifications, and quiescent current characteristics. Pin-for-pin compatibility is maintained.

Q: What is the significance of the propagation delay difference between the 74HC688N and SN74HC688N?

A: The SN74HC688N exhibits a maximum propagation delay of 36ns compared to 29ns for the 74HC688N, both measured at 6V with 50pF load. This 7ns difference is within typical manufacturing tolerance ranges for the 74HC logic family and does not affect functional operation in standard applications. Timing-critical designs should verify this specification against system requirements.

Q: Why is the CD74HC688E not recommended as a primary substitute?

A: The CD74HC688E is classified as obsolete and carries RoHS non-compliance status. While electrically equivalent, its obsolete designation indicates discontinued manufacturing and limited availability. RoHS non-compliance restricts use in applications subject to environmental regulations. The SN74HC688N is preferred due to active product status and full compliance certification.

Q: Are there temperature range limitations when substituting with the SN74HC688N?

A: The SN74HC688N operates across -40°C to 85°C, compared to the original 74HC688N range of -40°C to 125°C. Applications requiring operation above 85°C require thermal environment verification. Standard industrial and commercial temperature ranges are fully supported.

Q: Is the 20-DIP package format consistent across all substitute parts?

A: Yes, all substitute parts utilize the 20-DIP (0.300", 7.62mm) through-hole package with identical pin spacing and mechanical dimensions, ensuring direct board-level compatibility without layout modifications.