74HC/HCT85

General description

The 74HC/HCT85 are high-speed Si-gate CMOS devices and are pin compatible with low power Schottky TTL (LSTTL). They are specified in compliance with JEDEC standard no. 7A.

The 74HC/HCT85 are 4-bit magnitude comparators that can be expanded to almost any length. They perform comparison of two 4-bit binary, BCD or other monotonic codes and present the three possible magnitude results at the outputs (Q_A>B, Q_A=B and Q_A<B). The 4-bit inputs are weighted (A₀ to A₃ and B₀ to B₃), where A₃ and B₃ are the most significant bits.

The operation of the '85' is described in the function table, showing all possible logic conditions. The upper part of the table describes the normal operation under all conditions that will occur in a single device or in a series expansion scheme. In the upper part of the table the three outputs are mutually exclusive. In the lower part of the table, the outputs reflect the feed forward conditions that exist in the parallel expansion scheme.

For proper compare operation the expander inputs (I_A>B, I_A=B and I_A<B) to the least significant position must be connected as follows: I_A<B =I_A>B = = LOW and I_A=B = HIGH.

For words greater than 4-bits, units can be cascaded by connecting outputs Q_A<B, Q_A>B and Q_A=B to the corresponding inputs of the significant comparator.

Features

• Serial or parallel expansion without extra gating
• Magnitude comparison of any binary words
• Output capability: standard
• I_CC category: MSI

Products/packages

Pricing/ordering/availability

Design support

Support Documents

HCT_USER_GUIDE; HC/T User Guide (1997-11-01)

Parametrics/similar products

Similar products
74HC/HCT85 links to the similar products page containing an overview of products that are similar in function or related to the type number(s) as listed on this page. The similar products page includes products from the same catalog tree(s), relevant selection guides and products from the same functional category.

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