SN74CBT3257CPWR datasheet(2/19 Pages) TI

2 / 19 page

SN74CBT3257C

4BIT 1OF2 FET MULTIPLEXER/DEMULTIPLEXER

5V BUS SWITCH WITH 2V UNDERSHOOT PROTECTION

SCDS137 − OCTOBER 2003

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

description/ordering information (continued)

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

power off.

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.

FUNCTION TABLE

INPUTS

INPUT/OUTPUT

FUNCTION

INPUT/OUTPUT

FUNCTION

A port = B1 port

HB2

A port = B2 port

Disconnect

SN74CBT3257CPWR Datasheet(PDF) 2 Page - Texas Instruments