Fairchild MM74C85 Data Handbook
Summary
The MM74C85 is a reliable four-bit magnitude comparator designed for circuitry needing to compare two binary or BCD coded words. This component determines if input 'A' is greater than, less than, or equal to input 'B'. The manual provides comprehensive details on its operation, including truth tables, electrical characteristics, and guidelines for cascading multiple stages (N-bits). Ideal for digital logic design requiring high noise immunity, low power drain, and precise comparisons across a wide voltage range.
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74C 85 4-B it M ag itu e C arato
October 1987 Revised January 1999
MM74C85 4-Bit Magnitude Comparator
(VIN(1)) applied to the A = B input and low level voltage
General Description
(VIN(0)) applied to A > B and A < B inputs.
The MM74C85 is a four-bit magnitude comparator which will perform comparison of straight binary or BCD codes.
The circuit consists of eight comparing inputs (A0, A1, A2, Features
A3, B0, B1, B2, B3), three cascading inputs (A > B, A < B
Wide supply voltage range: 3.0V to 15V
and A = B), and three outputs (A > B, A < B and A = B).
Guaranteed noise margin: 1.0V
This device compares two four-bit words (A and B) and
High noise immunity: 0.4 VCC (typ.)
determines whether they are “greater than,” “less than,” or “equal to” each other by a high level on the appropriate out- Low power: TTL compatibility: put. For words greater than four-bits, units can be cas-
fan out of 2 driving 74L
caded by connecting the outputs (A > B, A < B, and A = B)
Expandable to 'N' stages
of the least significant stage to the cascade inputs (A > B, A
< B and A = B) of the next-significant stage. In addition the Applicable to binary or BCD
least significant stage must have a high level voltage Low power pinout: 74L85
Ordering Code: Order Number Package Number Package Description MM74C85N N16E 16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300” Wide
Connection Diagram
Pin Assignments for DIP
Top View
© 1999 Fairchild Semiconductor Corporation DS005886.prf www.fairchildsemi.com
Page Summary Contents For Fairchild MM74C85 Data Handbook
Manual Details
| Brand | Fairchild |
|---|---|
| Pages | 5 |
| File Size | 53.91 KB |
| Published | July 06, 2026 |
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Frequently Asked Questions
What is the function of the MM74C85?
It is a four-bit magnitude comparator that compares two four-bit words (A and B) to determine if they are 'greater than,' 'less than,' or 'equal to.'
What power supply voltage range can this device handle?
It operates across a wide supply voltage range from 3.0V to 15V.
How can I compare words greater than four bits?
Connect the outputs (A>B, A<B, and A=B) of lower-significance stages to the cascading inputs of the next higher-significance stage.
What are the recommended input voltage levels for operation?
Logical '1' input voltage is V = 5.0V, and Logical '0' input voltage is V = 5.0V (with minimums specified by respective tables).
Is this device compatible with BCD codes?
Yes, it can perform comparisons on both straight binary or BCD codes.