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Hitachi |
HD74HC148
8-to-3-line Octal Priority Encoder
Description
The HD74HC148 encodes eight data lines to three-line (4-2-1) binary (octal). Cascading circuitry (enable
input EI and enable output EO) is provided to allow octal expansion without the need for external circuitry.
The data inputs and outputs are active at the low logic level.
Features
• High Speed Operation: tpd (0 - 7 to A0 - A2) = 15 ns typ (CL = 50 pF)
• High Output Current: Fanout of 10 LSTTL Loads
• Wide Operating Voltage: VCC = 2 to 6 V
• Low Input Current: 1 µA max
• Low Quiescent Supply Current: ICC (static) = 4 µA max (Ta = 25°C)
Function Table
Inputs
Outputs
EI 0 1 2 3 4 5 6 7 A2 A1 A0 GS EO
HX X X X X X X X H H H H H
LH H H H H H H H H H H H L
LX X X X X X X L L L L L H
LX X X X X X L H L L H L H
LX X X X X L H H L H L L H
LX X X X L H H H L H H L H
LX X X L H H H H H L L L H
LX X L H H H H H H L H L H
LX L H H H H H H H H L L H
LL H H H H H H H H H H L H
H : High level
L : Low level
X : Irrelevant
HD74HC148
Pin Arrangement
41
52
Inputs
63
74
EI 5
Outputs
A2 6
A1 7
GND 8
4
5 EO
6 GS
73
EI 2
A2 1
A1 0
A0
(Top view)
16 VCC
15 EO
Outputs
14 GS
13 3
12 2
11 1
Inputs
10 0
9 A0 Output
2
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