Function and Pinout Compatible With FCT

and F Logic

25-Ω Output Series Resistors to Reduce

Transmission-Line Reflection Noise

TTL Output Level Versions of Equivalent

FCT Functions

Edge-Rate Control Circuitry for

Significantly Improved Noise

Characteristics

Ioff Supports Partial-Power-Down Mode

Operation

Fully Compatible With TTL Input and

Output Logic Levels

ESD Protection Exceeds JESD 22

– 2000-V Human-Body Model (A114-A)

– 200-V Machine Model (A115-A)

– 1000-V Charged-Device Model (C101)

12-mA Output Sink Current

15-mA Output Source Current

3-State Outputs

description

The CY74FCT2257T has four identical two-input multiplexers that select four bits of data from two sources

under the control of a common data-select (S) input. The I0 inputs are selected when S is low, and the I1 inputs

are selected when S is high. Data appears at the output in noninverted form for the CY74FCT2257T. On-chip

termination resistors at the outputs reduce system noise caused by reflections. The CY74FCT2257T can

replace the FCT257T to reduce noise in an existing design.

The CY74FCT2257T is a logic implementation of a four-pole, two-position switch, in which the position of the

switch is determined by the logic levels supplied to S. Outputs are forced to the high-impedance off state when

the output-enable (OE) input is high.

All but one device must be in the high-impedance state to prevent currents from exceeding the maximum ratings

if outputs are tied together. Design of the OE signals must ensure that there is no overlap when outputs of 3-state

devices are tied together.

This device is fully specified for partial-power-down applications using Ioff. The Ioff circuitry disables the outputs,

preventing damaging current backflow through the device when it is powered down.