FSTU3257QSCX

Overview

The onsemi FSTU3257QSCX is a quad 2:1 multiplexer/demultiplexer bus switch housed in a 16-lead Quarter Size Outline Package (QSOP). It operates within a supply voltage range of 4.0V to 5.5V and supports an operating temperature from -40°C to +85°C. The device features undershoot hardened ports capable of withstanding voltages down to -2.0V. Key electrical characteristics include a typical switch on resistance of 4Ω at 5.5V, low quiescent supply current of 3µA, and minimal propagation delay through the switch.

Feature Summary

• Undershoot hardened A and B ports support extended voltage ranges down to -2V below ground.
• Soft enable turn-on minimizes bus-to-bus charge sharing during activation.
• Low on-resistance allows signal connection without adding propagation delay or ground bounce noise.
• Control inputs are compatible with TTL logic levels.

Applications

• High-speed data routing in digital systems
• Bus switching applications requiring undershoot protection
• Multiplexing and demultiplexing signals in CMOS/TTL environments

Procurement Notes

Verify package authenticity as the QSCX suffix denotes the QSOP variant. Confirm RoHS compliance status via official documentation. Ensure sourcing channels provide valid traceability for automotive or industrial specifications if required by the design. Check for obsolescence notices given the component's history.

Selection Notes

Select this component when undershoot protection is critical for signal integrity. The QSOP package suits space-constrained designs compared to standard SOIC. Verify that the 4Ω on-resistance meets the specific load requirements of the application circuit.

Part Context

This part belongs to the FSTU series of high-speed CMOS bus switches. It shares functional similarities with other quad 2:1 mux/demux devices but distinguishes itself through integrated UHC technology for handling negative voltage transients on I/O lines.

Replacement Considerations

Direct substitutes include the FSTU3257MTCX (TSSOP) or FSTU3257MX (SOIC) for pin-compatible alternatives. Other FST series bus switches may require schematic review due to differing pinouts or electrical characteristics.

FAQ

What is the function of the UHC protection?

UHC (Undershoot Hardened Circuit) prevents voltage differentials from developing and turning on the switch during input transient voltage undershoot events, maintaining output signal integrity.

How does the OE pin control the switch?

When OE is LOW, the Select pin connects Port A to the selected Port B output. When OE is HIGH, the switch is open, creating a high-impedance state between the ports.