TECHNICAL DATA
IN74HC251A
8-Input Data Selector/Multiplexer
with 3-State Outputs
High-Performance Silicon-Gate CMOS
The IN74HC251A is identical in pinout to the LS/ALS251. The
device inputs are compatible with standard CMOS outputs; with pullup
resistors, they are compatible with LS/ALSTTL outputs.
The device selects one of the eight binary Data Inputs, as determined
by the Address Inputs. The Output Enable pin must be at a low level for
the selected data to appear at the outputs. If Output Enable is high, the Y
and the Y outputs are in the high-impedance state. This 3-State feature
allows the IN74HC251A to be used in bus-oriented systems.
•
Outputs Directly Interface to CMOS, NMOS, and TTL
•
Operating Voltage Range: 2.0 to 6.0 V
•
Low Input Current: 1.0
µA
•
High Noise Immunity Characteristic of CMOS Devices
ORDERING INFORMATION
IN74HC251AN Plastic
IN74HC251AD SOIC
T
A
= -55° to 125° C for all packages
PIN ASSIGNMENT
LOGIC DIAGRAM
FUNCTION TABLE
Inputs
A2
X
L
L
L
L
PIN 16 =V
CC
PIN 8 = GND
H
H
H
A1
X
L
L
H
H
L
L
H
A0
X
L
H
L
H
L
H
L
OE
H
L
L
L
L
L
L
L
Outputs
Y
Z
D0
D1
D2
D3
D4
D5
D6
Y
Z
D0
D1
D2
D3
D4
D5
D6
H H
H
L
D7
D7
D0,D1...D7=the level of the respective D
input
Z = high-impedance state
X = don’t care
Rev. 00
IN74HC251A
MAXIMUM RATINGS
*
Symbol
V
CC
V
IN
V
OUT
I
IN
I
OUT
I
CC
P
D
Tstg
T
L
*
Parameter
DC Supply Voltage (Referenced to GND)
DC Input Voltage (Referenced to GND)
DC Output Voltage (Referenced to GND)
DC Input Current, per Pin
DC Output Current, per Pin
DC Supply Current, V
CC
and GND Pins
Power Dissipation in Still Air, Plastic DIP+
SOIC Package+
Storage Temperature
Lead Temperature, 1 mm from Case for 10 Seconds
(Plastic DIP or SOIC Package)
Value
-0.5 to +7.0
-1.5 to V
CC
+1.5
-0.5 to V
CC
+0.5
±25
±50
±75
750
500
-65 to +150
260
Unit
V
V
V
mA
mA
mA
mW
°C
°C
Maximum Ratings are those values beyond which damage to the device may occur.
Functional operation should be restricted to the Recommended Operating Conditions.
+Derating - Plastic DIP: - 10 mW/°C from 65° to 125°C
SOIC Package: : - 7 mW/°C from 65° to 125°C
RECOMMENDED OPERATING CONDITIONS
Symbol
V
CC
V
IN
, V
OUT
T
A
t
r
, t
f
Parameter
DC Supply Voltage (Referenced to GND)
DC Input Voltage, Output Voltage (Referenced to GND)
Operating Temperature, All Package Types
Input Rise and Fall Time
(Figure 1)
V
CC
=2.0 V
V
CC
=4.5 V
V
CC
=6.0 V
Min
2.0
0
-55
0
0
0
Max
6.0
V
CC
+125
1000
500
400
Unit
V
V
°C
ns
This device contains protection circuitry to guard against damage due to high static voltages or electric fields.
However, precautions must be taken to avoid applications of any voltage higher than maximum rated voltages to this
high-impedance circuit. For proper operation, V
IN
and V
OUT
should be constrained to the range GND≤(V
IN
or
V
OUT
)≤V
CC
.
Unused inputs must always be tied to an appropriate logic voltage level (e.g., either GND or V
CC
). Unused
outputs must be left open.
Rev. 00
IN74HC251A
DC ELECTRICAL CHARACTERISTICS
(Voltages Referenced to GND)
V
CC
Symbol
Parameter
Test Conditions
V
Guaranteed Limit
25
°C
to
-55°C
1.5
3.15
4.2
0.3
0.9
1.2
1.9
4.4
5.9
3.98
5.48
0.1
0.1
0.1
0.26
0.26
±0.1
±0.5
≤85
°C
1.5
3.15
4.2
0.3
0.9
1.2
1.9
4.4
5.9
3.84
5.34
0.1
0.1
0.1
0.33
0.33
±1.0
±5.0
≤125
°C
1.5
3.15
4.2
0.3
0.9
1.2
1.9
4.4
5.9
3.7
5.2
0.1
0.1
0.1
0.4
0.4
±1.0
±10
µA
µA
V
Unit
V
IH
Minimum High-
Level Input Voltage
Maximum Low -
Level Input Voltage
Minimum High-
Level Output Voltage
V
OUT
=0.1 V or V
CC
-0.1 V
⎢I
OUT
⎢≤
20
µA
V
OUT
=0.1 V or V
CC
-0.1 V
⎢I
OUT
⎢ ≤
20
µA
V
IN
=V
IH
or V
IL
⎢I
OUT
⎢ ≤
20
µA
V
IN
=V
IH
or V
IL
⎢I
OUT
⎢ ≤
4.0 mA
⎢I
OUT
⎢ ≤
5.2 mA
2.0
4.5
6.0
2.0
4.5
6.0
2.0
4.5
6.0
4.5
6.0
2.0
4.5
6.0
4.5
6.0
6.0
6.0
V
V
IL
V
V
OH
V
V
OL
Maximum Low-
Level Output Voltage
V
IN
=V
IH
or V
IL
⎢I
OUT
⎢ ≤
20
µA
V
IN
=V
IH
or V
IL
⎢I
OUT
⎢ ≤
4.0 mA
⎢I
OUT
⎢ ≤
5.2 mA
I
IN
I
OZ
Maximum Input
Leakage Current
Maximum Three-
State Leakage
Current
Maximum Quiescent
Supply Current
(per Package)
V
IN
=V
CC
or GND
Output in High-Impedance
State
V
IN
= V
IL
or V
IH
V
OUT
=V
CC
or GND
V
IN
=V
CC
or GND
I
OUT
=0µA
I
CC
6.0
8.0
80
160
µA
Rev. 00
IN74HC251A
AC ELECTRICAL CHARACTERISTICS
(C
L
=50pF,Input t
r
=t
f
=6.0 ns)
V
CC
Symbol
Parameter
V
Guaranteed Limit
25
°C
to
-55°C
185
37
31
205
41
35
195
39
33
145
29
25
220
44
37
150
30
26
75
15
13
10
15
≤85°C
≤125°C
Unit
t
PLH
, t
PHL
Maximum Propagation Delay, Input D to
Output Y or Y (Figures 1,2 and 5)
Maximum Propagation Delay , Input A to
Output Y or Y (Figures 3 and 5)
Maximum Propagation Delay , Output Enable to
Output Y (Figures 4 and 6)
Maximum Propagation Delay , Output Enable to
Output Y (Figures 4 and 6)
Maximum Propagation Delay , Output Enable to
Output Y (Figures 4 and 6)
Maximum Propagation Delay , Output Enable to
Output Y (Figures 4 and 6)
Maximum Output Transition Time, Any Output
(Figures 1 and 6)
Maximum Input Capacitance
Maximum Three-State Output Capacitance
(Output in High-Impedance State)
Power Dissipation Capacitance (Per Package)
2.0
4.5
6.0
2.0
4.5
6.0
2.0
4.5
6.0
2.0
4.5
6.0
2.0
4.5
6.0
2.0
4.5
6.0
2.0
4.5
6.0
-
-
230
46
39
255
51
43
245
48
42
180
36
31
275
55
47
190
38
33
95
19
16
10
15
280
56
48
310
62
53
295
59
50
220
44
38
330
66
56
225
45
38
110
22
19
10
15
ns
t
PLH
, t
PHL
ns
t
PLZ
, t
PHZ
ns
t
PZL
, t
PZH
ns
t
PLZ
, t
PHZ
ns
t
PZL
, t
PZH
ns
t
TLH
, t
THL
ns
C
IN
C
OUT
pF
pF
Typical @25°C,V
CC
=5.0 V
36
pF
C
PD
Used to determine the no-load dynamic power
consumption: P
D
=C
PD
V
CC2
f+I
CC
V
CC
Figure 1. Switching Waveforms
Figure 2. Switching Waveforms
Rev. 00
IN74HC251A
Figure 3. Switching Waveforms
Figure 4. Switching Waveforms
Figure 5. Test Circuit
Figure 6.Test Circuit
EXPANDED LOGIC DIAGRAM
Rev. 00
单片机
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