IDT74FST6800

    The FST6800 belongs to IDT's family of Bus switches.  Bus switch devices perform the function of connecting or isolating two ports without providing any inherent current sink or source capability.  Thus they generate little or no noise of their own while providing a low resistance path for an external driver.  These devices connect input and output ports through an n-channel FET.  When the gate-to-source junction of this FET is adequately forward biased the device conducts and the resistance between input and output ports is small.  Without adequate bias on the gate to-source junction of the FET, the FET is turned off, therefore with no V_CC applied, the device has hot insertion capability.

    The low on-resistance and simplicity of the connection between input and output ports reduces the delay in this path to close to zero.

    The FST6800 provides a 10-Bit TTL-compatible interface.  The ON pin serves as the enable pin.  When ON is high, A and B ports are isolated and B outputs are precharged to the BIASV voltage, through the equivalent of a 10KΩ resistor.