HIT HD74HC257 Datasheet
HD74HC257
Quad. 2-to-1-line Data Selectors/Multiplexers
(with noninverted 3-state outputs)
Description
The large output drive capability coupled with the 3-state feature make this device ideal for interfacing with
bus lines in a bus organized system. When the output control input line is taken high, the outputs of all four
multiplexers are sent into a high impedance state. When the output control line is low, the select input
chooses whether the A or B input is used.
Features
• High Speed Operation: tpd (Data to Y) = 10.5 ns typ (CL = 50 pF)
• High Output Current: Fanout of 15 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
Output Control Select A B Y
LL L X L
LL H X H
LHXLL
LH X H H
H X X X High impedance
Notes H: high level, L: low level, X: irrelevant
HD74HC257
Pin Arrangement
Select
1A
1B
1Y
2A
2B
2Y
GND
1
S
2
3
4
5
6
7
1A
1B
1Y
2A
2B
2Y
3Y
OC
4A
4B
4Y
3A
3B
8
16
15
14
13
12
11
10
9
V
CC
Output
control
4A
4B
4Y
3A
3B
3Y
(Top view)
Absolute Maximum Ratings
Item Symbol Rating Unit
Supply voltage range V
Input voltage V
Output voltage V
DC current drain per pin I
DC current drain per VCC, GND ICC, I
DC input diode current I
DC output diode current I
Power dissipation per package P
CC
IN
OUT
OUT
GND
IK
OK
T
Storage temperature Tstg –65 to +150 °C
–0.5 to +7.0 V
–0.5 to VCC + 0.5 V
–0.5 to VCC + 0.5 V
±35 mA
±75 mA
±20 mA
±20 mA
500 mW
2
Logic Diagram
1A
1B
2A
2B
3A
3B
4A
HD74HC257
V
CC
1Y
V
CC
2Y
V
CC
3Y
V
CC
4Y
Select
Output
control
4B
3
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