DM74LS243N

Overview

The DM74LS243N is a quadruple bus transceiver manufactured by onsemi (formerly Fairchild) in a 14-lead Plastic Dual-In-Line (PDIP) package. It operates within a supply voltage range of 4.75V to 5.25V and supports an operating temperature range of 0°C to +70°C. The device features three-state outputs with a low-level output current of 24 mA and a high-level output current of -15 mA. Propagation delay times are specified at 18 ns for both LOW-to-HIGH and HIGH-to-LOW transitions under standard load conditions.

Feature Summary

• Enables asynchronous two-way communication between data buses
• Utilizes PNP inputs to reduce DC loading on the bus line
• Incorporates hysteresis at data inputs to improve noise margin

Applications

• Asynchronous two-way communications between data buses
• Driving terminated lines down to 133Ω

Procurement Notes

Verify the specific manufacturer origin, as the component was originally produced by Fairchild Semiconductor before acquisition by onsemi. Confirm that the PDIP package variant matches the N14A designation. Ensure compliance with life support policies, as the datasheet explicitly prohibits use in critical life support devices without written approval from the manufacturer's president.

Selection Notes

Select this component when designing systems requiring isolated bidirectional data transfer with reduced bus loading. The inclusion of input hysteresis makes it suitable for environments with potential signal noise. Verify that the required propagation delay meets system timing constraints, particularly noting the difference between standard and heavy capacitive loads.

Part Context

This part belongs to the 74LS logic family, characterized by Low-power Schottky technology. It serves as a functional equivalent to other quadruple bus transceivers within the industry-standard 74xx series, providing a reliable solution for interfacing different digital logic blocks or memory systems.

Replacement Considerations

Direct substitutes include the SN74LS243 from Texas Instruments. Other compatible options within the same logic family may be considered if pinout and electrical characteristics align perfectly.

FAQ

What is the purpose of the hysteresis feature in this transceiver?

Hysteresis at the data inputs improves the noise margin, allowing the device to function reliably in environments with signal interference.

Can this device drive terminated transmission lines?

Yes, the datasheet specifies that the transceiver can be used to drive terminated lines down to 133Ω impedance.