1CY74FCT2257T
Data sheet acquired from Cypress Semiconductor Corporation.
Data sheet modi鏗乪d to remove devices not offered.
CY74FCT2257T
SCCS038 - September 1994 - Revised March 2000
Quad 2-Input Multiplexer
Functional Description
The FCT2257T has four identical two-input multiplexers that
select four bits of data from two sources under the control of a
common data Select input (S). The I0 inputs are selected
when the Select input is LOW and the I1 inputs are selected
when the Select input is HIGH. Data appears at the output in
true non-inverted form for the FCT2257T. On-chip termination
resistors have been added to the outputs to reduce system
noise caused by re鏗俥ctions. The FCT2257T can be used to
replace the FCT257T to reduce noise in an existing design.
The FCT2257T is a logic implementation of a four-pole,
two-position switch where the position of the switch is
determined by the logic levels supplied to the select input. Out-
puts are forced to a high-impedance 鈥淥FF鈥?state when the
Output Enable input (OE) is HIGH.
All but one device must be in the high-impedance state to
avoid currents exceeding the maximum ratings if outputs are
tied together. Design of the output enable signals must ensure
that there is no overlap when outputs of three-state devices
are tied together.
The outputs are designed with a power-off disable feature to
allow for live insertion of boards.
Features
鈥?Function and pinout compatible with FCT and F logic
鈥?/div>
25鈩?output series resistors to reduce transmission line
re鏗俥ction noise
鈥?FCT-C speed at 4.3 ns max.,
FCT-A speed at 5.0 ns max.
鈥?TTL output level versions of equivalent FCT functions
鈥?Edge-rate control circuitry for signi鏗乧antly improved
noise characteristics
鈥?Power-off disable feature
鈥?Fully compatible with TTL input and output logic levels
鈥?ESD > 2000V
鈥?/div>
Sink current 12 mA
Source current15 mA
鈥?Extended commercial temp. range of 鈥?0藲C to +85藲C
鈥?Three-state outputs
Logic Block Diagram
I
0a
I
1a
I
0b
I
1b
I
0c
I
1c
I
0d
I
1d
S
Pin Configurations
SOIC/QSOP
Top View
OE
S
I
0a
I
1a
Y
a
I
0b
I
1b
Y
b
GND
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
V
CC
OE
I
0c
I
1c
Y
c
I
0d
I
1d
Y
d
FCT2257T
鈥?
Y
a
Y
b
Y
c
Y
d
FCT2257T
鈥?
Pin Description
Name
I
S
OE
Y
Data Inputs
Common Select Input
Enable Inputs (Active LOW)
Data Outputs
Description
Function Table
[1]
Inputs
OE
H
L
L
L
L
S
X
H
H
L
L
I
0
X
X
X
L
H
I
1
X
L
H
X
X
Output
Y
Z
L
H
L
H
Note:
1. H = HIGH Voltage Level, L = LOW Voltage Level, X = Don鈥檛 Care,
Z = High impedance (OFF) state.
Copyright
漏
2000, Texas Instruments Incorporated
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