FST3126MX

Overview

The FST3126MX is a 4-bit bus switch IC manufactured by onsemi, derived from Fairchild Semiconductor technology. It provides four high-speed CMOS TTL-compatible bus switches with low on-resistance to connect inputs to outputs without adding propagation delay or generating ground bounce noise. The device operates within a supply voltage range of 4.0V to 5.5V and features separate OE inputs for each switch. When enabled, it offers minimal propagation delay and zero bounce in flow-through mode.

Feature Summary

• Provides four independent 1-bit bus switches with separate output enable (OE) inputs for precise control.
• Features low on-resistance to connect ports without adding propagation delay or generating additional ground bounce noise.
• Control inputs are compatible with TTL levels, ensuring seamless integration with standard logic families.

Applications

• High-speed data bus switching applications requiring minimal signal distortion.
• Systems utilizing TTL-compatible logic interfaces where low propagation delay is critical.
• Portable electronic devices benefiting from low quiescent supply current operation.

Procurement Notes

Verify the specific package variant (SOIC, TSSOP, or QSOP) required for your design, as the 'X' suffix indicates tape and reel availability. Confirm that the updated part numbering reflects ON Semiconductor's system requirements following the Fairchild integration. Ensure all unused control inputs are tied high or low to prevent floating states during operation.

Selection Notes

Select this component when designing circuits that require isolated bus segments with fast switching speeds and low power consumption. The device supports a wide operating temperature range suitable for industrial environments. Consider the specific package dimensions and pinout configurations available for SOIC, TSSOP, and QSOP formats to match PCB layout constraints.

Part Context

This device belongs to the FST series of bus switches, which utilizes proven CMOS technology for high-speed performance. It is part of onsemi's standard product portfolio, maintaining compatibility with legacy Fairchild designs while adhering to current manufacturing standards. The family is designed for applications demanding reliable signal integrity and low noise characteristics.

Replacement Considerations

Check the ON Semiconductor website for updated ordering codes due to the transition from Fairchild nomenclature. Verify pin-to-pin compatibility if substituting from other manufacturers' 4-bit bus switches. Ensure that the replacement device meets the same voltage and temperature specifications for your application.

FAQ

How does the FST3126 handle unused control inputs?

Unused control inputs must be held high or low; they may not float to ensure proper device operation and prevent unintended switching states.

What is the propagation delay characteristic of this bus switch?

The device contributes no propagation delay other than the RC delay of the typical on-resistance and load capacitance when driven by an ideal voltage source.