SN54LS348 [MOTOROLA]
8-INPUT PRIORITY ENCODERS WITH 3-STATE OUTPUTS; 具有三态输出8输入优先级编码器
| 型号： | SN54LS348 |
| 厂家： | 
MOTOROLA |
| 描述： | 8-INPUT PRIORITY ENCODERS WITH 3-STATE OUTPUTS |
| 文件： | 总6页 (文件大小：219K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
SN54/74LS348
SN54/74LS848
8-INPUT PRIORITY ENCODERS
WITH 3-STATE OUTPUTS
The SN54/74LS348 and the SN54/74LS848 are eight input priority encod-
ers which provide the 8-line to 3-line function.
The outputs (A0–A2) and inputs (0–7) are active low. The active low input
which has the highest priority (input 7 has the highest) is represented on the
outputs (output A0 is the lowest bit). An example would be if inputs 1, 2 and 4
were low, then a binary 4 would be represented on the outputs.
The GS (Group Signal) output is active low when any of the inputs are low. It
serves to indicate when any of the inputs are active.
8-INPUT PRIORITY ENCODERS
WITH 3-STATE OUTPUTS
LOW POWER SCHOTTKY
A0, A1 and A2 are three-state outputs. This allows for up to 64 line expan-
sion without the need for special external circuitry.
A logical one on the Enable Input (EI) forces A0, A1 ared A2 to the disabled
state and outputs GS and EO to the high state. A high on all data inputs (0–7)
together with a low on the EI input disables outputs A0, A1, and A2 and forces
output GS to the high state and output EO to the low state.
Use of the EI input in conjunction with the EO output provides for the capa-
bility of having priority encoding of n input signals.
J SUFFIX
CERAMIC
CASE 620-09
16
1
TheLS848hasspecialinternalcircuitryprovidingforagreatlyreducedneg-
ative going glitch on the GS (Group Signal) output and on a reduced tendency
for the A0, A1 and A2 outputs to become momentarily enabled. Both of these
occurrenceshappenwhentheEIinputgoesfromalogicalonetoalogicalzero
and all data inputs (0–7) are held at logical ones. The internal glitch reduction
circuitry does add an additional fan-in of one on all data inputs (compared to
that of the LS348).
N SUFFIX
PLASTIC
CASE 648-08
16
1
D SUFFIX
SOIC
CASE 751B-03
16
1
ORDERING INFORMATION
SN54LSXXXJ
Ceramic
SN74LSXXXN Plastic
SN74LSXXXD SOIC
FUNCTION TABLE
INPUTS
OUTPUTS
EI
0
1
2
3
4
5
6
7
A2 A1 A0 GS EO
H
L
L
L
L
L
L
L
L
L
X
H
X
X
X
X
X
X
X
L
X
H
X
X
X
X
X
X
L
X
H
X
X
X
X
X
L
X
H
X
X
X
X
L
H
H
H
X
H
X
X
X
L
H
H
H
H
X
H
X
X
L
H
H
H
H
H
X
H
X
L
H
H
H
H
H
H
X
H
L
H
H
H
H
H
H
H
Z
Z
L
L
L
Z
Z
L
Z
Z
L
H
L
H
L
H
L
H
H
L
L
L
L
L
L
L
L
H
L
H = HIGH Logic Level
L = LOW Logic Level
X = Irrelevant
H
H
H
H
H
H
H
H
L
Z = High Impedance State
H
H
L
L
H
H
L
H
H
H
H
H
H
H
H
FAST AND LS TTL DATA
5-499
SN54/74LS348 • SN54/74LS848
BLOCK DIAGRAMS
″
′
′
′
′
′
′
′
′
′
′
′
SN54/74LS348
SN54/74LS848
GUARANTEED OPERATING RANGES
Symbol
Parameter
Min
Typ
Max
Unit
V
CC
Supply Voltage
54
74
4.5
4.75
5.0
5.0
5.5
5.25
V
T
A
Operating Ambient Temperature Range
54
74
–55
0
25
25
125
70
°C
I
I
Output Current — High
Output Current — High
EO, GS
54, 74
–0.4
mA
mA
OH
A0, A1, A2
A0, A1, A2
54
74
–1.0
–2.6
OH
I
Output Current — Low
Output Current — Low
EO, GS
54
74
4.0
8.0
mA
mA
OL
OL
I
A0, A1, A2
A0, A1, A2
54
74
12
24
FAST AND LS TTL DATA
5-500
SN54/74LS348 • SN54/74LS848
DC CHARACTERISTICS OVER OPERATING TEMPERATURE RANGE (unless otherwise specified)
Limits
Min
Typ
Max
Symbol
Parameter
Input HIGH Voltage
Unit
Test Conditions
Guaranteed Input HIGH Voltage for
All Inputs
V
2.0
V
IH
54
74
0.7
0.8
Guaranteed Input LOW Voltage for
All Inputs
V
V
Input LOW Voltage
V
V
IL
Input Clamp Diode Voltage
–0.65
–1.5
V
CC
= MIN, I = –18 mA
IN
IK
Output HIGH Voltage
A0, A1, A2
54, 74
54
2.4
2.5
2.7
3.1
3.5
3.5
V
V
V
V
= MIN, I
OH
= MAX, V = V
IN
CC
IH
V
OH
or V per Truth Table
IL
EO, GS
EO, GS
74
V
V
= V
CC
MIN,
= V or V
IL IH
54, 74
74
0.25
0.35
0.25
0.35
0.4
0.5
0.4
0.5
V
V
V
V
I
I
I
I
= 4.0 mA
= 8.0 mA
= 12 mA
= 24 mA
CC
IN
OL
OL
OL
OL
Output LOW Voltage
EO, GS
V
V
OL
per Truth Table
V
CC
V
IN
= V
MIN,
= V or V
54, 74
74
CC
Output LOW Voltage
A0, A1, A2
IL
IH
OL
per Truth Table
I
I
Output Off Current HIGH
Output Off Current LOW
20
µA
µA
V
= MAX, V
= MAX, V
= 2.7 V
= 0.4 V
OZH
CC
CC
OUT
–20
V
OZL
OUT
Input HIGH Current
Input 0, EI — LS348
20
40
µA
µA
Input 0 — LS848
V
CC
V
CC
V
CC
= MAX, V = 2.7 V
IN
Other — LS348
Other — LS848
40
60
µA
µA
I
IH
Input HIGH Current
Input 0, EI — LS348
0.1
0.2
mA
mA
Input 0 — LS848
= MAX, V = 7.0 V
IN
Other — LS348
Other — LS848
0.2
0.3
mA
mA
Input LOW Current
Input 0, EI — LS348
–0.4
–0.8
mA
mA
Input 0 — LS848
I
IL
= MAX, V = 0.4 V
IN
Other — LS348
Other — LS848
–0.8
–1.2
mA
mA
Short Circuit Current (Note 1)
–20
–30
–120
–130
mA
mA
I
I
V
V
= MAX
= MAX
EO, GS
A0, A1, A2
OS
CC
Power Supply Current
Total, Output HIGH
CC
12
13
23
25
All Inputs and Outputs Open
mA
CC
V
= MAX, Inputs 7, EI = GND
CC
All Others Open
Total, Output LOW
Note 1: Not more than one output should be shorted at a time, nor for more than 1 second.
FAST AND LS TTL DATA
5-501
SN54/74LS348 • SN54/74LS848
AC CHARACTERISTICS (V
= 5.0 V, T = 25°C)
A
CC
LS348
Limits
LS848
Limits
From
(Input)
To
(Output)
Min Typ Max Min Typ Max
Symbol
Waveform
In-Phase
output
Unit
Test Conditions
t
t
11
20
23
23
25
24
11
26
38
9.0
11
14
17
25
18
23
17
30
35
35
39
41
18
40
55
21
17
36
21
40
27
35
12
20
23
23
25
24
11
26
38
9.0
11
14
17
30
18
23
18
30
35
35
39
41
18
40
55
21
17
36
21
45
27
35
PLH
1 thru 7
1 thru 7
EI
A0, A1 or A2
A0, A1 or A2
A0, A1 or A2
E0
ns
PHL
t
t
t
t
t
t
t
t
t
t
t
t
t
t
Out-of-Phase
output
PLH
PHL
PZH
PZL
PLH
PHL
PLH
PHL
PLH
PHL
PLH
PHL
PHZ
PLZ
C
R
= 45 pF
= 667 Ω
L
L
ns
ns
ns
ns
ns
ns
ns
Out-of-Phase
output
0 thru 7
0 thru 7
EI
In-Phase
output
GS
C
R
= 15 pF
= 2.0 Ω
L
L
In-Phase
output
GS
In-Phase
output
EI
EO
C
R
= 5.0 pF
= 667 Ω
L
L
EI
A0, A1 or A2
FAST AND LS TTL DATA
5-502
Case 751B-03 D Suffix
16-Pin Plastic
SO-16
-A-
16
1
9
8
P
C
-B-
R X 45°
G
-T-
J
M
F
D
°
°
°
°
K
Case 648-08 N Suffix
16-Pin Plastic
-A-
16
1
9
B
S
8
F
L
C
K
-T-
M
H
J
G
D
°
°
°
°
Case 620-09 J Suffix
16-Pin Ceramic Dual In-Line
-A-
16
9
-B-
1
8
L
C
-T-
K
M
N
E
J
F
G
D
°
°
°
°
FAST AND LS TTL DATA
5-503
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