FSTU6800WMX

Overview

The FSTU6800WMX is a 10-bit bus switch in a 24-lead SOIC package. It operates with a supply voltage of 4.0V to 5.5V and features a typical on-resistance of 4Ω at 4.5V. The device supports inputs up to 5.5V and includes undershoot protection down to -2.0V. Propagation delay is typically 0.25ns, with input/output capacitance at 5pF. Quiescent current is 3µA. It enables zero-bounce flow-through switching and precharges outputs via a selectable BiasV pin.

Feature Summary

• Undershoot hardened circuit protection allows operation with signals extending 2.0V below ground without triggering the switch.
• Integrated output precharge mechanism minimizes live insertion noise by biasing the B Port through an equivalent resistor when disabled.
• Soft enable turn-on functionality reduces bus-to-bus charge sharing during activation to maintain signal integrity.

Applications

• High-speed CMOS TTL-compatible bus switching
• Systems requiring extended input range support
• Applications minimizing live insertion noise

Procurement Notes

Verify the specific suffix 'WMX' against manufacturer documentation, as standard datasheets list 'WM'. Confirm package dimensions match M24B (SOIC) requirements. Ensure operating conditions remain within the 4.0V to 5.5V supply range. Check for AEC qualification status if automotive use is intended, as this variant may lack explicit certification data in general references.

Selection Notes

Select this component for designs requiring low propagation delay and minimal ground bounce. The 4Ω on-resistance supports high-current switching without significant voltage drop. The dedicated BiasV pin allows flexible precharge voltage selection. Ensure control inputs are compatible with TTL levels for proper OE signal handling.

Part Context

This device belongs to the Fairchild Switch family, utilizing proven switch technology similar to the FST3384. It provides 10 bits of switching capability in a compact surface-mount package. The product line focuses on high-speed data routing with low power consumption and robust input protection features.

Replacement Considerations

Direct substitutes include the FSTU6800QSC (QSOP) and FSTU6800MTC (TSSOP). Verify pin compatibility and package footprint before substitution. Functional equivalence exists across these variants, but physical mounting constraints must be addressed.

FAQ

How does the device handle undershoot?

The integrated Undershoot Hardened Circuit (UHC) senses undershoot at the I/Os and prevents voltage differentials from developing, allowing safe operation down to -2.0V.

What is the function of the BiasV pin?

When the switch is open (OE HIGH), the BiasV pin precharges the B Port to a selectable bias voltage through an equivalent 10-kΩ resistor to minimize live insertion noise.