HIT HD74HC148 Datasheet
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
EI01234567A
HXXXXXXXXHHHHH
LHHHHHHHHHHHHL
LXXXXXXXLLLLLH
LXXXXXXLHLLHLH
LXXXXXLHHLHLLH
LXXXXL HHHLHHLH
LXXXLHHHHHLLLH
LXXLHHHHHHLHLH
LXL HHHHHHHHLLH
LLHHHHHHHHHHLH
H : High level
L : Low level
X : Irrelevant
A1A0GS EO
2
HD74HC148
Pin Arrangement
Inputs
Outputs
EI
A
A1
GND
1
4
2
5
4
5
EO
16
15
V
EO
CC
Outputs
3
6
4
7
5
6
7
EI
GS
14
GS
13
12
3
2
3
2
Inputs
2
6
2
7
A
A1
8
1
0
0
A
11
10
1
0
9
Output
A
0
(Top view)
2
HD74HC148
DC Characteristics
Ta = –40 to
Ta = 25°C
Item Symbol V
Input voltage V
IH
(V) Min Typ Max Min Max Unit Test Conditions
CC
2.0 1.5 — — 1.5 — V
4.5 3.15 — — 3.15 —
6.0 4.2 — — 4.2 —
V
IL
2.0 — — 0.5 — 0.5 V
4.5 — — 1.35 — 1.35
6.0 — — 1.8 — 1.8
Output voltage V
OH
2.0 1.9 2.0 — 1.9 — V Vin = VIH or VILIOH = –20 µA
4.5 4.4 4.5 — 4.4 —
6.0 5.9 6.0 — 5.9 —
4.5 4.18 — — 4.13 — IOH = –4 mA
6.0 5.68 — — 5.63 — IOH = –5.2 mA
V
OL
2.0 — 0.0 0.1 — 0.1 V Vin = VIH or VILIOL = 20 µA
4.5 — 0.0 0.1 — 0.1
6.0 — 0.0 0.1 — 0.1
4.5 — — 0.26 — 0.33 IOL = 4 mA
6.0 — — 0.26 — 0.33 IOL = 5.2 mA
Input current Iin 6.0 — — ±0.1 — ±1.0 µA Vin = VCC or GND
Quiescent supply
I
CC
6.0 — — 4.0 — 40 µA Vin = VCC or GND, Iout = 0 µA
current
+85°C
3
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