DM74LS245N

Overview

The DM74LS245N is a 3-STATE octal bus transceiver manufactured by onsemi, formerly Fairchild Semiconductor. It operates within a supply voltage range of 4.75 V to 5.25 V and supports an operating temperature range of 0°C to +70°C. The device features 8 channels with TTL input/output levels and provides a maximum low-level output current (IOL) of 24 mA and a maximum high-level output current (IOH) of -15 mA. Propagation delay times are typically 8 ns, with maximum delays of 12 ns at 45 pF load and 16–17 ns at 150 pF load.

Feature Summary

• Bi-directional data transmission between two buses controlled by the DIR input
• Three-state outputs allow direct driving of bus lines while isolating inactive devices
• PNP inputs reduce DC loading on connected bus lines
• Input hysteresis improves noise margins for reliable signal reception

Applications

• Asynchronous bidirectional data communication between data buses
• Memory interface circuits in microprocessor systems
• High-density digital logic interconnects requiring bus isolation

Procurement Notes

Verify that the component matches the specific N20A package designation for the 20-lead Plastic Dual-In-Line configuration. Confirm the manufacturer origin as onsemi or its predecessor Fairchild Semiconductor to ensure accurate datasheet alignment. Check for any suffix variations such as 'X' which indicate tape and reel packaging instead of standard tube delivery.

Selection Notes

Select this component when designing asynchronous bus architectures requiring true bi-directional flow without external timing constraints. The PNP input structure offers lower DC loading compared to standard NPN alternatives. Ensure the application environment remains within the specified 0°C to +70°C temperature range and utilizes a 5V nominal power supply.

Part Context

This device belongs to the 74LS series of logic integrated circuits, characterized by Low-power Schottky technology. It serves as a fundamental building block for parallel data transfer in legacy and industrial control systems. The octal configuration allows simultaneous handling of eight-bit words across shared communication pathways.

Replacement Considerations

SN74LS245N Texas Instruments

FAQ

How does the enable input affect the bus state?

When the enable input (G) is held high, the device disables, placing all outputs in a high-impedance state to effectively isolate the A and B buses from each other.

What determines the direction of data flow?

Data transmission direction is controlled by the DIR input; a low level directs data from Bus A to Bus B, while a high level directs data from Bus B to Bus A.