The SN74CB3Q6800 is a high-bandwidth FET bus switch utilizing a charge pump to elevate the gate voltage
of the pass transistor, providing a low and flat ON-state resistance (ron). The low and flat ON-state resistance
allows for minimal propagation delay and supports rail-to-rail switching on the data input/output (I/O) ports. The
device also features low data I/O capacitance to minimize capacitive loading and signal distortion on the data
bus. Specifically designed to support high-bandwidth applications, the SN74CB3Q6800 provides an optimized
interface solution ideally suited for broadband communications, networking, and data-intensive computing
The SN74CB3Q6800 is a 10-bit bus switch with a single output-enable (ON\) input. When ON\ is low, the 10-bit
bus switch is ON and the A port is connected to the B port, allowing bidirectional data flow between ports. When
ON\ is high, the 10-bit bus switch is OFF and a high-impedance state exists between the A and B ports. The B
port is precharged to bias voltage (BIASV) through the equivalent of a 10-k resistor when ON\ is high, or if the
device is powered down (VCC = 0 V).
During insertion (or removal) of a card into (or from) an active bus, the cards output voltage may be close to
GND. When the connector pins make contact, the cards parasitic capacitance tries to force the bus signal to
GND, creating a possible glitch on the active bus. This glitching effect can be reduced by using a bus switch
with precharged bias voltage (BIASV) of the bus switch equal to the input threshold voltage level of the receivers
on the active bus. This method will ensure that any glitch produced by insertion (or removal) of the card will not
cross the input threshold region of the receivers on the active bus, minimizing the effects of live-insertion noise.
This device is fully specified for partial-power-down applications using Ioff. The Ioff circuitry prevents damaging
current backflow through the device when it is powered down. The device has isolation during power off.
To ensure the high-impedance state during power up or power down, ON\ should be tied to VCC through a pullup
resistor; the minimum value of the resistor is determined by the current-sinking capability of the driver.
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