74HC85; 74HCT85
4-bit magnitude comparator
Rev. 3 — 20 April 2018 Product data sheet
1 General description
The 74HC85; 74HCT85 is a 4-bit magnitude comparator 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. 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.
Inputs include clamp diodes. This enables the use of current limiting resistors to interface
inputs to voltages in excess of V
CC
.
2 Features and benefits
• Wide supply voltage range from 2.0 to 6.0 V
• CMOS low power dissipation
• High noise immunity
• Latch-up performance exceeds 100 mA per JESD 78 Class II Level B
• Input levels:
– For 74HC85: CMOS level
– For 74HCT85: TTL level
• Complies with JEDEC standard: no. 7A
– JESD8C (2.7 V to 3.6 V)
– JESD7A (2.0 V to 6.0 V)
• ESD protection:
– HBM JESD22-A114-A exceeds 2000 V
– MM JESD22-A115-A exceeds 200 V
• Specified from -40 °C to +85 °C and from -40 °C to +125 °C
3 Applications
• Process controllers
• Servo-motor control
