74F138PCX View Datasheet(PDF) - Fairchild Semiconductor
Part Name
Description
View to exact match
74F138PCX Datasheet PDF : 7 Pages
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Unit Loading/Fan Out
Pin Names
Description
A0–A2
E1, E2
E3
O0–O7
Address Inputs
Enable Inputs (Active LOW)
Enable Input (Active HIGH)
Outputs (Active LOW)
Truth Table
Inputs
E1
E2
E3
A0
A1
A2
O0
H
X
X
X
X
X
H
X
H
X
X
X
X
H
X
X
L
X
X
X
H
L
L
H
L
L
L
L
L
L
H
H
L
L
H
L
L
H
L
H
L
H
L
L
H
H
H
L
H
L
L
H
L
L
H
H
L
L
H
H
L
H
H
L
L
H
L
H
H
H
L
L
H
H
H
H
H
H = HIGH Voltage Level
L = LOW Voltage Level
X = Immaterial
Functional Description
The F138 high-speed 1-of-8 decoder/demultiplexer
accepts three binary weighted inputs (A0, A1, A2) and,
when enabled, provides eight mutually exclusive active
LOW outputs (O0–O7). The F138 features three Enable
inputs, two active LOW (E1, E2) and one active HIGH (E3).
All outputs will be HIGH unless E1 and E2 are LOW and E3
is HIGH. This multiple enable function allows easy parallel
U.L.
HIGH/LOW
1.0/1.0
1.0/1.0
1.0/1.0
50/33.3
Input IIH/IIL
Output IOH/IOL
20 µA/−0.6 mA
20 µA/−0.6 mA
20 µA/−0.6 mA
−1 mA/20 mA
Outputs
O1
O2
O3
O4
O5
O6
O7
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
L
H
H
H
H
H
H
H
L
H
H
H
H
H
H
H
L
H
H
H
H
H
H
H
L
H
H
H
H
H
H
H
L
H
H
H
H
H
H
H
L
H
H
H
H
H
H
H
L
expansion of the device to a 1-of-32 (5 lines to 32 lines)
decoder with just four F138 devices and one inverter (See
Figure 1). The F138 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.
www.fairchildsemi.com
FIGURE 1. Expansion to 1-of-32 Decoding
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