The LCX257 is a quad 2-input multiplexer with 3-STATE
outputs. It selects four bits of data from two sources under
control of a Common Data Select input. When the Select
input is LOW, the I
0x
inputs are selected and when Select
is HIGH, the I
1x
inputs are selected. The data on the
selected inputs appears at the outputs in true (non
inverted) form. The device is the logic implementation of a
4-pole, 2-position switch where the position of the switch is
determined by the logic levels supplied to the Select input.
The logic equations for the outputs are shown below:
Z
a
=
OE • (1
1a
• S
+
I
0a
• S)
Z
b
=
OE • (1
1b
• S
+
I
0b
• S)
Z
c
=
OE • (1
1c
• S
+
I
0c
• S)
Z
d
=
OE • (1
1d
• S
+
I
0d
• S)
When the Output Enable (OE) is HIGH, the outputs are
forced to a high impedance state. If the outputs are tied
together, all but one device must be in the high impedance
state to avoid high currents that would exceed the maxi-
mum ratings. Designers should ensure the Output Enable
signals to 3-STATE devices whose outputs are tied
together are designed so there is no overlap.
Truth Table
Output
Enable
OE
H
L
L
L
L
H
=
HIGH Voltage Level
L
=
LOW Voltage Level
X
=
Immaterial
Z
=
High Impedance
Select
Input
S
X
H
H
L
L
I
0
X
X
X
L
H
Data
Inputs
I
1
X
L
H
X
X
Outputs
Z
Z
L
H
L
H
Logic Diagram
Please note that this diagram is provided only for the understanding of logic operations and should not be used to estimate propagation delays.
www.fairchildsemi.com
2
74LCX257
Absolute Maximum Ratings
(Note 1)
Symbol
V
CC
V
I
V
O
I
IK
I
OK
I
O
I
CC
I
GND
T
STG
Parameter
Supply Voltage
DC Input Voltage
DC Output Voltage
DC Input Diode Current
DC Output Diode Current
DC Output Source/Sink Current
DC Supply Current per Supply Pin
DC Ground Current per Ground Pin
Storage Temperature
Value
Conditions
Units
V
V
Output in 3-STATE
Output in HIGH or LOW State (Note 2)
V
I
<
GND
V
O
<
GND
V
O
>
V
CC
V
mA
mA
mA
mA
mA
−
0.5 to
+
7.0
−
0.5 to
+
7.0
−
0.5 to
+
7.0
−
0.5 to V
CC
+
0.5
−
50
−
50
+
50
±
50
±
100
±
100
−
65 to
+
150
°
C
Recommended Operating Conditions
(Note 4)
Symbol
V
CC
V
I
V
O
I
OH
/I
OL
Supply Voltage
Input Voltage
Output Voltage
Output Current
HIGH or LOW State
3-STATE
V
CC
=
3.0V
−
3.6V
V
CC
=
2.7V
−
3.0V
V
CC
=
2.3V
−
2.7V
T
A
Free-Air Operating Temperature
Input Edge Rate, V
IN
=
0.8V–2.0V, V
CC
=
3.0V
Parameter
Operating
Data Retention
Min
2.0
1.5
0
0
0
Max
3.6
3.6
5.5
V
CC
5.5
Units
V
V
V
±
24
±
12
±
8
−
40
0
85
10
mA
°
C
ns/V
∆
t/
∆
V
Note 2:
The Absolute Maximum Ratings are those values beyond which the safety of the device cannot be guaranteed. The device should not be operated
at these limits. The parametric values defined in the Electrical Characteristics tables are not guaranteed at the Absolute Maximum Ratings. The “Recom-
mended Operating Conditions” table will define the conditions for actual device operation.
Note 3:
I
O
Absolute Maximum rating must be observed.
Note 4:
Unused Inputs must be held HIGH or LOW. They may not float.
DC Electrical Characteristics
Symbol
V
IH
V
IL
V
OH
Parameter
HIGH Level Input Voltage
LOW Level Input Voltage
HIGH Level Output Voltage
I
OH
= −100 µA
I
OH
= −8
mA
I
OH
= −12
mA
I
OH
= −18
mA
I
OH
= −24
mA
V
OL
LOW Level Output Voltage
I
OL
=
100
µA
I
OL
=
8 mA
I
OL
=
12 mA
I
OL
=
16 mA
I
OL
=
24 mA
I
I
I
OZ
I
OFF
Input Leakage Current
3-STATE Output Leakage
Power-Off Leakage Current
0
≤
V
I
≤
5.5V
0
≤
V
O
≤
5.5V
V
I
=
V
IH
or V
IL
V
I
or V
O
=
5.5V
Conditions
V
CC
(V)
2.3
−
2.7
2.7
−
3.6
2.3
−
2.7
2.7
−
3.6
2.3
−
3.6
2.3
2.7
3.0
3.0
2.3
−
3.6
2.3
2.7
3.0
3.0
2.3
−
3.6
2.3
−
3.6
0
V
CC
−
0.2
1.8
2.2
2.4
2.2
0.2
0.6
0.4
0.4
0.55
±5.0
±5.0
10
µA
µA
µA
V
V
T
A
= −40°C
to
+85°C
Min
1.7
2.0
0.7
0.8
Max
Units
V
V
3
www.fairchildsemi.com
74LCX257
DC Electrical Characteristics
Symbol
I
CC
∆I
CC
Parameter
Quiescent Supply Current
Increase in I
CC
per Input
(Continued)
V
CC
(V)
2.3
−
3.6
2.3
−
3.6
2.3
−
3.6
T
A
= −40°C
to
+85°C
Min
Max
10
±10
500
µA
µA
Conditions
V
I
=
V
CC
or GND
3.6V
≤
V
I
, V
O
≤
5.5V (Note 5)
V
IH
=
V
CC
−0.6V
Units
Note 5:
Outputs disabled or 3-STATE only.
AC Electrical Characteristics
T
A
= −40°C
to
+85°C,
R
L
=
500
Ω
Symbol
Parameter
V
CC
=
3.3V
±
0.3V
C
L
=
50 pF
Min
t
PHL
t
PLH
t
PHL
t
PLH
t
PZL
t
PZH
t
PLZ
t
PHZ
t
OSHL
t
OSLH
Propagation Delay
S→Z
n
Propagation Delay
I
n
→Z
n
Output Enable Time
OE
→Z
n
Output Disable Time
OE
→Z
n
Output to Output Skew (Note 6)
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
Max
7.0
7.0
6.0
6.0
7.0
7.0
5.5
5.5
1.0
1.0
V
CC
=
2.7V
C
L
=
50 pF
Min
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
Max
8.5
8.5
6.5
6.5
8.5
8.5
6.0
6.0
V
CC
=
2.5V
±
0.2V
C
L
=
30 pF
Min
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
Max
9.1
9.1
7.2
7.2
9.1
9.1
6.6
6.6
ns
ns
ns
ns
ns
Units
Note 6:
Skew is defined as the absolute value of the difference between the actual propagation delay for any two separate outputs of the same device. The
specification applies to any outputs switching in the same direction, either HIGH-to-LOW (t
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