onsemi 74HC244DTR2G Octal Buffer/Line Driver: Datasheet, Pinout, and Application Circuits
The 74HC244DTR2G from onsemi is a high-speed octal buffer and line driver integrated circuit belonging to the 74HC family of high-speed CMOS logic. This device is engineered to provide high noise immunity and low power consumption, typical of CMOS technology, while offering the ability to drive highly capacitive or relatively low-impedance loads. It is an essential component for a wide range of digital systems, serving as a vital interface between different subsystems.
Datasheet Overview: Key Specifications
The datasheet for the 74HC244DTR2G outlines its critical electrical and operational characteristics. Key parameters include a wide operating voltage range from 2.0 V to 6.0 V, allowing for compatibility with various logic levels, including 3.3V and 5V systems. It features high-current outputs capable of driving up to 15 LSTTL loads, making it excellent for bus driving. The device boasts typical propagation delays of just 13 ns, ensuring high-speed operation. Furthermore, its balanced propagation delays and low quiescent current make it ideal for power-sensitive applications. The "DTR2G" suffix denotes that it is supplied in a TSSOP-20 package, which is surface-mount and space-efficient, suitable for modern, compact PCB designs.
Pinout and Functional Description
The 74HC244 is an octal buffer, meaning it contains eight independent buffer gates. These are split into two groups of four, each controlled by its own Output Enable (OE) pin. This structure provides significant flexibility in bus management.
Pins 1, 19 (1OE, 2OE): Active-Low Output Enable inputs. When 1OE is held low, the four buffers connected to pins 2-4 and 6-8 (1A1-1A4 and 1Y1-1Y4) are enabled. Similarly, a low on 2OE enables the second group (pins 11-13 and 15-17: 2A1-2A4 and 2Y1-2Y4). A high logic level on an OE pin places its corresponding outputs in a high-impedance state, effectively disconnecting them from the bus.
A Inputs (1A1-1A4, 2A1-2A4): The input pins for the buffers.
Y Outputs (1Y1-1Y4, 2Y1-2Y4): The output pins. The logic signal present at an A input is reproduced at its corresponding Y output when the respective OE is active.
Pin 10 (GND): Ground.
Pin 20 (VCC): Positive supply voltage.
Application Circuits
The primary function of the 74HC244 is to isolate and drive signals. Its non-inverting nature makes it perfect for these key applications:
1. Microprocessor Bus Buffering and Driving: A primary use case is interfacing a microprocessor's address or data bus with multiple memory chips or peripherals. The 74HC244 isolates the CPU from the capacitive load of the bus, preventing signal degradation and ensuring data integrity. The independent output enable pins allow different sections of the bus to be enabled or tri-stated as needed.
2. Line Driving for Long Cables: When sending digital signals over longer distances, such as through ribbon cables or backplanes, signal integrity can be compromised. The 74HC244's strong output drive capability helps overcome capacitance and inductance, ensuring a clean signal arrives at the destination.
3. Input/Output Port Expansion: It can be used to increase the number of output ports available from a microcontroller. The tri-state feature allows multiple devices to share a common bus without interference.
4. Waveform Generation: Its high-speed capability makes it suitable for generating and shaping clock signals and other digital waveforms.
ICGOODFIND Summary
The onsemi 74HC244DTR2G is a robust and versatile octal buffer/line driver that remains a fundamental component in digital design. Its combination of high-speed operation, significant output drive strength, and tri-state functionality makes it indispensable for bus interface applications, signal isolation, and driving heavy loads. The TSSOP package ensures it meets the demands of space-constrained modern electronics. For engineers designing digital systems, the 74HC244 offers a reliable and efficient solution for ensuring signal integrity and proper system interfacing.
Keywords: Octal Buffer, Line Driver, Tri-State Output, Bus Interface, CMOS Logic
