MC74HCT245AF

Overview

The MC74HCT245AF is an octal bus transceiver manufactured by onsemi, belonging to the HCT logic series. It features eight independent non-inverting channels with three-state outputs, designed for bidirectional asynchronous data communication between buses. The device operates within a supply voltage range of 4.5 V to 5.5 V and accepts TTL-compatible input levels while driving CMOS loads. It utilizes a 20-pin SOIC surface-mount package and ensures high noise immunity with low power dissipation characteristics typical of silicon-gate CMOS technology.

Feature Summary

• Provides bidirectional data transfer capability across eight parallel channels controlled by a single direction pin.
• Features three-state outputs that allow electrical isolation of the bus when the output enable signal is deactivated.
• Ensures compatibility with LSTTL inputs and direct interfacing with CMOS, NMOS, and TTL output stages.

Applications

• Interfacing TTL or NMOS outputs to High Speed CMOS inputs as a level converter.
• Two-way asynchronous communication between data buses in computing systems.
• Memory address drivers and data bus controllers in industrial control applications.

Procurement Notes

Verify the specific suffix 'AF' against the manufacturer's current datasheet to confirm package dimensions and tape-and-reel specifications. Ensure the procurement source provides valid RoHS compliance documentation. Cross-reference the part number with the official onsemi ordering information to distinguish it from similar variants like the MC74HCT245ADWG or MM74HCT245MTC, which may have different thermal or mechanical properties.

Selection Notes

Select this component when designing systems requiring robust interface between legacy TTL logic and modern CMOS circuits. The HCT series is appropriate for applications needing standard 5V operation with defined noise margins. Consider the 20-pin SOIC footprint for space-constrained printed circuit board layouts. Evaluate the propagation delay specifications if timing constraints are critical for the synchronous or asynchronous data paths involved.

Part Context

This device is part of the widely adopted 74HCT logic family, serving as a digital buffer and transceiver. It shares pinout compatibility with the older LS245 standard, facilitating design upgrades without altering existing board layouts. The component represents a standard solution for managing data flow in microprocessor-based systems where multiple devices share a common data bus structure.

Replacement Considerations

The MM74HCT245MTC offers identical logical functionality but utilizes a TSSOP-20 package instead of SOIC. Designers must verify pin-to-pin compatibility and ensure the alternative package fits the available PCB real estate. Other equivalents within the same logic family should be checked for matching voltage ranges and drive capabilities before substitution.