Datasheet

www.fairchildsemi.com 2
74LCX138
Connection Diagrams
Pin Assignments for SOIC, SOP, and TSSOP
Pad Assignments for DQFN
(Top Through View)
Pin Descriptions
Functional Description
The LCX138 high-speed 1-of-8 decoder/demultiplexer
accepts three binary weighted inputs (A
0
, A
1
, A
2
) and,
when enabled, provides eight mutually exclusive active-
LOW outputs (O
0
–O
7
). The LCX138 features three Enable
inputs, two active-LOW (E
1
, E
2
) and one active-HIGH (E
3
).
All outputs will be HIGH unless E
1
and E
2
are LOW and E
3
is HIGH. The LCX138 can be used as an 8-output demulti-
plexer by using one of the active LOW Enable inputs as the
data input and the other Enable inputs as strobes. The
Enable inputs which are not used must be permanently tied
to their appropriate active-HIGH or active-LOW state.
Truth Table
H = HIGH Voltage Level
L = LOW Voltage Level
X = Immaterial
Pin Names Description
A
0
–A
2
Address Inputs
E
1
–E
2
Enable Inputs
E
3
Enable Input
O
0
–O
7
Outputs
Inputs Outputs
E
1
E
2
E
3
A
0
A
1
A
2
O
0
O
1
O
2
O
3
O
4
O
5
O
6
O
7
HXXXXXHHHHHHHH
XHXXXXHHHHHHHH
XXLXXXHHHHHHHH
LLHLLLLHHHHHHH
L LHHL LHLHHHHHH
L LHLHLHHLHHHHH
LLHHHLHHHLHHHH
L LHL LHHHHHLHHH
L LHHLHHHHHHLHH
L LHLHHHHHHHHLH
L LHHHHHHHHHHHL
(Bottom View)
DAP No Connect
Note: DAP (Die Attach Pad)