The Fairchild Switch FSTU32X800 provides 20-bits of high-speed CMOS TTL-compatible bus switching. The low On Resistance of the switch allows inputs to be connected to outputs without adding propagation delay or generating additional ground bounce noise. The A and B Ports are protected against undershoot to support an extended range to 2.0V below ground. Fairchild's integrated Undershoot Hardened Circuit (UHC) senses undershoot at the I/O and responds by preventing voltage differentials from developing and turning the switch on. The device also precharges the B Port to a selectable bias voltage (BiasV) to minimize live insertion noise. The device is organized as two 10-bit switches with a bus enable (OEn) signal. When OEn is LOW, the switch is ON and Port A is connected to Port B. When OEn is HIGH, the switch is OPEN and the B Port is precharged to BiasV through an equivalent 10-k resistor.