Datasheet

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DESCRIPTION/ORDERING INFORMATION (CONTINUED)
V
CC
≈V
CC
5.5 V
0 V
NOTE A: If the input high voltage (V
IH
) level is greater than or equal to V
CC
– 1 V, and less than or equal to 5.5 V, then the output high voltage
(V
OH
) level will be equal to approximately the V
CC
voltage level.
Input Voltages Output Voltages
0 V
≈V
CC
– 1 V ≈V
CC
– 1 V
V
CC
IN OUT
CB3T
SN74CB3T3257
4-BIT 1-OF-2 FET MULTIPLEXER/DEMULTIPLEXER
2.5-V/3.3-V LOW-VOLTAGE BUS SWITCH WITH 5-V-TOLERANT LEVEL SHIFTER
SCDS149 – OCTOBER 2003 – REVISED MARCH 2005
The SN74CB3T3257 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 I
off
. The I
off
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 V
CC
through a pullup
resistor; the minimum value of the resistor is determined by the current-sinking capability of the driver.
FUNCTION TABLE
(EACH MULTIPLEXER/DEMULTIPLEXER)
INPUTS
INPUT/OUTPUT
FUNCTION
A
OE S
L L B1 A port = B1 port
L H B2 A port = B2 port
H X Z Disconnect
Figure 1. Typical DC Voltage Translation Characteristics
2