The ’HC85 and ’HCT85 are high speed magnitude comparators that use silicon-gate CMOS technology to achieve operating speeds similar to LSTTL with the low power consumption of standard CMOS integrated circuits.
These 4-bit devices compare two binary, BCD, or other monotonic codes and present the three possible magnitude results at the outputs (A > B, A < B, and A = B). The 4-bit input words are weighted (A0 to A3 and B0 to B3), where A3 and B3 are the most significant bits.
The devices are expandable without external gating, in both serial and parallel fashion. The upper part of the truth table indicates operation using a single device or devices in a serially expanded application. The parallel expansion scheme is described by the last three entries in the truth table.
Buffered Inputs and Outputs
Typical Propagation Delay: 13ns (Data to Output at VCC = 5V, CL = 15pF, TA = 25°C
Serial or Parallel Expansion Without External Gating
Fanout (Over Temperature Range)
Standard Outputs. . . . . . . 10 LSTTL Loads
Bus Driver Outputs. . . . . 15 LSTTL Loads
Wide Operating Temperature Range . . . –55°C to 125°C
Balanced Propagation Delay and Transition Times
Significant Power Reduction Compared to LSTTL Logic ICs
2V to 6V Operation
High Noise Immunity: NIL = 30%, NIH = 30%of VCC at VCC = 5V
4.5V to 5.5V Operation
Direct LSTTL Input Logic Compatibility, VIL = 0.8V (Max), VIH = 2V (Min)