The SN74CBT3257C is a high-speed TTL-compatible FET multiplexer/demultiplexer with low ON-state
resistance (ron), allowing for minimal propagation delay. Active Undershoot-Protection Circuitry on the A and
B ports of the SN74CBT3257C provides protection for undershoot up to 2 V by sensing an undershoot event
and ensuring that the switch remains in the proper OFF state.
The SN74CBT3257C is a 4-bit 1-of-2 multiplexer/demultiplexer with a single output-enable (OE\) input. The
select (S) input controls the data path of the multiplexer/demultiplexer. When OE\ is low, the
multiplexer/demultiplexer is enabled and the A port is connected to the B port, allowing bidirectional data flow
between ports. When OE\ is high, the multiplexer/demultiplexer is disabled and a high-impedance state exists
between the A and B ports.
This device is fully specified for partial-power-down applications using Ioff. The Ioff feature ensures that
damaging current will not backflow through the device when it is powered down. The device has isolation during
To ensure the high-impedance state during power up or power down, OE\ 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.