Overview
The CD74HC85E is a high-speed 4-bit magnitude comparator produced by Texas Instruments. This device utilizes silicon-gate CMOS technology to achieve operating speeds similar to LSTTL logic while maintaining the low power consumption characteristic of standard CMOS integrated circuits. It compares two binary, BCD, or other monotonic codes and provides three possible magnitude results at the outputs: A > B, A < B, and A = B. The device is expandable in both serial and parallel configurations without the need for external gating.
Key Specifications
| Parameter | Min | Typ | Max | Unit |
|---|---|---|---|---|
| Supply Voltage Range (HC types) | 2 | 6 | V | |
| Supply Voltage Range (HCT types) | 4.5 | 5.5 | V | |
| Input or Output Voltage | 0 | VCC | V | |
| Propagation Delay (An, Bn to (A > B) OUT, (A < B) OUT) at VCC = 5V, CL = 15pF | 13 | 39 | ns | |
| Propagation Delay (An, Bn to (A = B) OUT) at VCC = 5V, CL = 15pF | 14 | 35 | ns | |
| Operating Temperature Range | -55 | 125 | ℃ | |
| Input Leakage Current | ±1 | μA | ||
| Supply Current | 80 | μA | ||
| Package Type | PDIP (16 pins) | |||
| Body Size (NOM) | 19.31 mm × 6.35 mm |
Key Features
- Buffered inputs and outputs
- Typical propagation delay: 13 ns (data to output at VCC = 5 V, CL = 15 pF, TA = 25℃)
- 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℃ to 125℃
- Balanced propagation delay and transition times
- Significant power reduction compared to LSTTL logic ICs
- HC types: 2 V to 6 V operation, High noise immunity: NIL = 30%, NIH = 30% of VCC at VCC = 5 V
- HCT types: 4.5 V to 5.5 V operation, Direct LSTTL input logic compatibility, VIL = 0.8 V (max), VIH = 2 V (min)
Applications
The CD74HC85E is suitable for various digital logic applications where high-speed magnitude comparison is required. It can be used in:
- Binary, BCD, or other monotonic code comparisons
- Serial and parallel data processing systems
- High-speed digital logic circuits
- Automotive and industrial control systems where a wide operating temperature range is necessary
- Any application requiring low power consumption and high noise immunity
Q & A
- What is the primary function of the CD74HC85E?
The CD74HC85E is a 4-bit magnitude comparator that compares two binary, BCD, or other monotonic codes and provides the results as A > B, A < B, and A = B. - What is the typical propagation delay of the CD74HC85E?
The typical propagation delay is 13 ns at VCC = 5 V, CL = 15 pF, and TA = 25℃. - What are the operating voltage ranges for HC and HCT types?
HC types operate from 2 V to 6 V, while HCT types operate from 4.5 V to 5.5 V. - What is the fanout capability of the CD74HC85E?
The device can drive up to 10 LSTTL loads for standard outputs and up to 15 LSTTL loads for bus driver outputs. - What is the operating temperature range of the CD74HC85E?
The device operates over a temperature range of -55℃ to 125℃. - Can the CD74HC85E be expanded in serial or parallel configurations?
Yes, the device can be expanded in both serial and parallel configurations without the need for external gating. - What are the key features of the HC and HCT types in terms of noise immunity and input compatibility?
HC types have high noise immunity (NIL = 30%, NIH = 30% of VCC at VCC = 5 V), while HCT types have direct LSTTL input logic compatibility (VIL = 0.8 V max, VIH = 2 V min). - What is the package type and body size of the CD74HC85E?
The CD74HC85E comes in a PDIP (16 pins) package with a body size of 19.31 mm × 6.35 mm. - What are some common applications of the CD74HC85E?
It is used in binary, BCD, or other monotonic code comparisons, serial and parallel data processing systems, high-speed digital logic circuits, and automotive and industrial control systems. - How does the CD74HC85E compare to LSTTL logic ICs in terms of power consumption?
The CD74HC85E offers significant power reduction compared to LSTTL logic ICs.
