CY74FCT2257ATQCT屬于集成電路（IC）的信號開關(guān)多路復(fù)用器解碼器。由美國德州儀器公司制造生產(chǎn)的CY74FCT2257ATQCT信號開關(guān)，多路復(fù)用器，解碼器邏輯型信號開關(guān)、多路復(fù)用器和編碼器 IC 可用于對以數(shù)字格式表示數(shù)據(jù)的電信號進(jìn)行路由和選擇。這些器件與設(shè)計(jì)用于模擬信號的類似產(chǎn)品有所不同，它們保留的信息表示為兩個(gè)電狀態(tài)之一，而不是兩個(gè)外部界限內(nèi)的無窮變化量。

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.