MM74HC688N Equivalent & Substitute Parts

Part Overview

The MM74HC688N is an 8-bit identity comparator manufactured by onsemi, designed for magnitude comparison applications with active low output. This logic component operates across a 2V to 6V supply voltage range and is housed in a 20-DIP package for through-hole mounting. The part is currently classified as obsolete, making equivalent substitutes necessary for ongoing design support and component sourcing.

Substiute Parts

MM74HC688N

onsemiIn Stock: 2219MM74HC688N Datasheet

Current PartRFQ

CD74HC688E

Harris CorporationIn Stock: 1869CD74HC688E Datasheet

SimilarRFQ

SN74HC688N

Texas InstrumentsIn Stock: 7729SN74HC688N Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the MM74HC688N is determined by strict adherence to the following electrical and mechanical parameters:

Critical Matching Parameters:

• Number of Bits: 8
• Output Function: A=B (Active Low)
• Voltage - Supply: 2V ~ 6V
• Package / Case: 20-DIP (0.300", 7.62mm)
• Mounting Type: Through Hole
• Base Product Number: 74HC688 series

Acceptable Variation Parameters:

• Max Propagation Delay: Must not exceed specified limits for the application
• Operating Temperature: May extend beyond the original range
• Current - Output High, Low: Must match 5.2mA specification
• Current - Quiescent (Iq): Must match 8 µA specification

All identified substitutes maintain identical core functionality and package specifications, ensuring direct replacement capability in existing designs.

Parameter Comparison

Engineering Selection Recommendations

SN74HC688N (Texas Instruments) is the preferred substitute for new designs and ongoing production. This part maintains active product status, ensuring long-term availability and supply chain stability. The SN74HC688N meets ROHS3 compliance requirements, supporting modern manufacturing and environmental standards. Propagation delay of 36ns remains within acceptable operational parameters for most applications utilizing the 74HC688 series.

CD74HC688E (Harris Corporation) provides an alternative with superior propagation delay performance at 29ns and extended operating temperature range (-55°C ~ 125°C). However, this part carries obsolete status and RoHS non-compliance designation, limiting its suitability for new designs requiring regulatory compliance.

MM74HC688N (onsemi) remains viable for legacy system maintenance where existing inventory is available. The 30ns propagation delay and standard operating temperature range align with typical 74HC688 application requirements.

Frequently Asked Questions (FAQ)

Q: Can SN74HC688N directly replace MM74HC688N in existing designs? A: Yes. Both parts share identical electrical specifications (8-bit identity comparator, A=B active low output, 2V-6V supply, 5.2mA output current, 8µA quiescent current) and 20-DIP through-hole packaging. The 36ns propagation delay of the SN74HC688N is compatible with MM74HC688N applications.

Q: What is the significance of propagation delay differences between substitutes? A: Propagation delay values (MM74HC688N: 30ns, CD74HC688E: 29ns, SN74HC688N: 36ns) represent the time required for output response to input changes. All values remain within the 74HC688 series specification envelope and are suitable for standard logic comparison applications. Design-critical timing applications should verify specific delay requirements.

Q: Why is SN74HC688N recommended over CD74HC688E despite slower propagation delay? A: SN74HC688N carries active product status and ROHS3 compliance certification, ensuring ongoing availability and regulatory alignment. CD74HC688E, while offering faster propagation delay, is obsolete and RoHS non-compliant, presenting supply chain and compliance risks.

Q: Are there package or mounting differences between these substitutes? A: No. All three parts use identical 20-DIP (0.300", 7.62mm) through-hole packaging, enabling direct socket replacement without PCB modification.

Q: What operating temperature range should be specified for applications using these substitutes? A: For maximum compatibility across all substitutes, specify -40°C ~ 85°C. CD74HC688E supports extended range (-55°C ~ 125°C) if required by application environment.