MM74C85N Magnitude Comparator - Equivalent & Substitute Parts

Part Overview

The MM74C85N is a 4-bit magnitude comparator manufactured by onsemi, designed to compare two 4-bit binary words and provide three output functions: A<B, A=B, and A>B. This device operates with active low outputs and is housed in a 16-PDIP package suitable for through-hole mounting.

The MM74C85N is classified as obsolete. Locating equivalent substitute parts is necessary to support legacy system maintenance, design updates, and continued production of equipment utilizing this comparator architecture.

Substiute Parts

MM74C85N

onsemiIn Stock: 1167MM74C85N Datasheet

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CD4585BE

Texas InstrumentsIn Stock: 9419CD4585BE Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution of the MM74C85N is determined by the following critical parameters:

• Functional equivalence: 4-bit magnitude comparator with A<B, A=B, A>B output functions
• Package compatibility: 16-DIP (0.300", 7.62mm) through-hole package
• Operating temperature range: -55°C to 125°C
• Supply voltage range: Minimum 3V to 15V overlap required
• Output logic level: Active high or active low configurations acceptable with circuit design consideration

The CD4585BE from Texas Instruments meets these substitution criteria. Both devices provide identical functional outputs, operate across overlapping supply voltage ranges, and are housed in the same 16-DIP package format. The primary design consideration is the output logic polarity difference: MM74C85N uses active low outputs while CD4585BE uses active high outputs, requiring circuit-level logic inversion if direct pin-for-pin replacement is intended.

Parameter Comparison

Engineering Selection Recommendations

The CD4585BE is an active substitute for the MM74C85N based on the following factors:

Product Status: The CD4585BE maintains active product status with Texas Instruments, ensuring continued availability and manufacturing support. The MM74C85N is obsolete, making the CD4585BE the preferred long-term solution for new designs and legacy system updates.

Compliance and Certifications: Both devices share identical REACH and ECCN classifications (REACH Unaffected, EAR99), ensuring equivalent regulatory compliance. The CD4585BE carries ROHS3 compliance certification, meeting modern environmental standards.

Functional Compatibility: Both devices provide identical magnitude comparison functions across the full operating temperature range of -55°C to 125°C. The 16-DIP package format is identical, supporting direct physical replacement in through-hole applications.

Design Consideration: The output logic polarity difference (active low vs. active high) requires evaluation at the circuit level. If the receiving logic expects active low signals, inverting logic gates or pull-up resistor configurations may be necessary. If the receiving logic is configurable or already accommodates active high signals, direct substitution is feasible without modification.

Frequently Asked Questions (FAQ)

Q: Can the CD4585BE replace the MM74C85N in a direct pin-for-pin substitution?

A: Physical pin-for-pin replacement is possible due to identical 16-DIP packaging. However, the output logic polarity differs: MM74C85N outputs are active low while CD4585BE outputs are active high. Circuit-level logic inversion may be required depending on the receiving circuit design.

Q: What is the primary reason to substitute the MM74C85N?

A: The MM74C85N is obsolete. The CD4585BE is an active product from Texas Instruments, ensuring continued availability, manufacturing support, and compliance with current environmental standards.

Q: Are the operating temperature ranges compatible?

A: Yes. Both devices operate across the identical temperature range of -55°C to 125°C, ensuring thermal compatibility in all specified operating conditions.

Q: How do the supply voltage ranges compare?

A: The MM74C85N operates from 3V to 15V, while the CD4585BE operates from 3V to 18V. The CD4585BE provides a wider upper voltage limit, offering greater flexibility in supply voltage selection while maintaining full overlap with the original device specification.

Q: What are the propagation delay differences?

A: The CD4585BE exhibits faster propagation delay (160ns @ 15V, 50pF) compared to the MM74C85N (300ns @ 10V, 50pF). This represents improved performance in timing-critical applications.

Q: Are there output current differences?

A: Yes. The MM74C85N provides higher output current capability (15mA high, 16mA low) compared to the CD4585BE (4.2mA high and low). Applications requiring high output current may require additional buffering with the CD4585BE.