FSTU3125QSCX

Overview

The FSTU3125QSCX is a high-speed CMOS quadruple bus switch manufactured by Fairchild Semiconductor. It provides four independent one-bit switches with separate active-low output enable inputs, packaged in a 14-pin SOIC. The device features low on-resistance to connect ports without adding propagation delay or ground bounce noise. It includes undershoot protection for A and B ports down to -2V using integrated Undershoot Hardened Circuitry. Control inputs are TTL-compatible, and the device operates within an industrial temperature range of -40°C to +85°C.

Feature Summary

• Undershoot hardened to -2V on all switch ports
• Minimal propagation delay through the switch
• Low power consumption with low Icc
• Zero bounce in flow-through mode

Applications

• System isolation and protection
• Voltage translation between logic levels
• Hot-swapping and hot-docking interfaces

Procurement Notes

Verify the specific suffix QSCX against the manufacturer's official ordering information to confirm package type and tape-and-reel specifications. Ensure the component matches the required operating temperature range and pin configuration for your circuit design before procurement.

Selection Notes

Select this component when undershoot protection is required for signals swinging below ground potential. It serves as a direct replacement for standard bus switches lacking hardening, suitable for applications involving live insertion or voltage level shifting where signal integrity is critical.

Part Context

This part belongs to the FST (QuickSwitch) family derived from Fairchild’s proven switch technology. It shares functional similarities with the FST3125 but adds specific undershoot protection capabilities. The device is designed to replace discrete logic gates, reducing board space and capacitance while maintaining high-speed performance.

Replacement Considerations

The FST3125M is a related variant offering similar switching functionality. Verify if the specific -2V undershoot protection is mandatory for the application; if not, standard variants may suffice.