onsemi MC74HC244ADW Octal Buffer/Line Driver: Datasheet, Pinout, and Application Circuits

The onsemi MC74HC244ADW is a high-speed Octal Buffer and Line Driver integrated circuit belonging to the 74HC high-speed CMOS logic family. This device is engineered to provide high noise immunity and low power consumption, typical of CMOS technology, while offering speeds comparable to LSTTL logic. It is an essential component for digital systems requiring signal isolation, amplification, or bus driving capabilities.

This IC features eight inverting buffers/line drivers with 3-state outputs. These outputs can be placed in a high-impedance state, effectively disconnecting them from the bus or line they are driving. This functionality is crucial for preventing bus contention in multi-point or bidirectional data transfer systems, such as those found in microprocessors and microcontrollers.

Key Datasheet Specifications:

Logic Type: CMOS

Number of Channels: 8

Input Level: CMOS

Output Level: CMOS

Output Type: 3-State

Supply Voltage - Operating: 2 V to 6 V

Propagation Delay Time: 13 ns typical at 5V

High-Level Output Current: -6 mA

Low-Level Output Current: 6 mA

Package: 20-SOIC (DW)

Pinout Configuration (MC74HC244ADW):

Housed in a 20-pin SOIC package, the pinout is logically organized into two independent groups of four buffers, each controlled by its own Output Enable (OE) pin.

Pin 1 (1OE): Output Enable for buffers 1-4 (Active LOW)

Pins 2-9 (1A1-1A4, 2A1-2A4): Inputs for the eight buffers

Pins 18-11 (1Y1-1Y4, 2Y1-2Y4): Outputs for the eight buffers (Note the order)

Pin 10 (GND): Ground

Pin 20 (VCC): Positive Supply Voltage (2V to 6V)

Pin 19 (2OE): Output Enable for buffers 5-8 (Active LOW)

Application Circuits:

1. Microprocessor Data Bus Buffering: The primary application of the MC74HC244ADW is to act as an interface between a microprocessor's data bus and multiple peripheral devices. It isolates the bus from high capacitance loads, preventing signal degradation and ensuring data integrity. The 3-state control allows the microprocessor to communicate with one peripheral at a time without interference.

2. Line Driving for Long Traces: When signals need to travel across a PCB or through cables over longer distances, they can suffer from attenuation and noise pickup. This octal buffer amplifies digital signals to restore their integrity, making it ideal for driving address buses, clock lines, or data lines to other boards or connectors.

3. Input/Output Port Expansion: For microcontrollers with a limited number of I/O pins, the '244 can be used to read multiple digital input signals (e.g., from switches or sensors). The outputs are enabled only when the microcontroller needs to read the state, allowing multiple devices to share the same input lines.

ICGOODFIND Summary:

The onsemi MC74HC244ADW is a robust and versatile octal buffer integral to modern digital design. Its ability to provide high-current drive, essential isolation, and 3-state bus interface capabilities makes it a fundamental solution for enhancing signal integrity and managing data flow in complex electronic systems, from industrial controls to consumer electronics.

Keywords:

1. Octal Buffer

2. 3-State Output

3. Line Driver

4. CMOS Logic

5. Bus Interface