MOTOROLA MC74ACT257MEL, MC74ACT257DR2, MC74ACT257D, MC74ACT257ML1, MC74ACT257ML2 Datasheet
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Quad 2 Input Multiplexer with 3 State Outputs
The MC74AC257/74ACT257 is a quad 2-input multiplexer with 3-state outputs. Four bits of data from two sources can be selected using a Common Data Select input. The four outputs present the selected data in true (noninverted) form. The outputs may be switched to a high impedance state by placing a logic HIGH on the common Output Enable (OE) input, allowing the outputs to interface directly with bus-oriented systems.
•Multiplexer Expansion by Tying Outputs Together
•Noninverting 3-State Outputs
•Outputs Source/Sink 24 mA
•′ACT257 Has TTL Compatible Inputs
VCC |
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OE |
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I0c |
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I1c |
Zc |
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I0d |
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I1d |
Zd |
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PIN NAMES |
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S |
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Common Data Select Input |
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OE |
3-State Output Enable Input |
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I0a±I0d |
Data Inputs from Source 0 |
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1 |
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4 |
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6 |
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7 |
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8 |
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I1a±I1d |
Data Inputs from Source 1 |
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S |
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I0a |
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I1a |
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Za |
I0b |
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I1b |
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Zb |
GND |
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Za±Zd |
3-State Multiplexer Outputs |
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TRUTH TABLE |
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Output |
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Select |
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Data |
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Outputs |
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Enable |
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Input |
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Inputs |
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OE |
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S |
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I0 |
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I1 |
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Z |
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H |
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X |
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X |
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X |
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Z |
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L |
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H |
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X |
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L |
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H |
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X |
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H |
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H |
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L |
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L |
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X |
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L |
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L |
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H |
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X |
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H |
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H = HIGH Voltage Level
L = LOW Voltage Level
X = Immaterial
Z = High Impedance
MC74AC257
MC74ACT257
QUAD 2-INPUT
MULTIPLEXER WITH 3-STATE OUTPUTS
N SUFFIX
CASE 648-08
PLASTIC
D SUFFIX
CASE 751B-05
PLASTIC
LOGIC SYMBOL
OE I0a I1a I0b I1b I0c I1c I0d I1d
S
Za |
Zb |
Zc |
Zd |
FACT DATA
5-1
MC74AC257 MC74ACT257
FUNCTIONAL DESCRIPTION
The MC74AC257/74ACT257 is a quad 2-input multiplexer with 3-state outputs. It selects four bits of data from two sources under control of a Common Data Select input. When the Select input is LOW, the I0x inputs are selected and when Select is HIGH, the I1x inputs are selected. The data on the selected inputs appears at the outputs in true (noninverted) form. The device is the logic implementation of a 4-pole, 2-position switch where the position of the switch is determined by the logic levels supplied to the Select input. The logic equations for the outputs are shown below:
Za = OE•(I1a•S+I0a•S)
Zb = OE•(I1b•S+I0b•S)
Zc = OE•(I1c•S+I0c•S)
Zd = OE•(I1d•S+I0d•S)
When the Output Enable input (OE) is HIGH, the outputs are forced to a high impedance state. If the outputs are tied together, all but one device must be in the high impedance state to avoid high currents that would exceed the maximum ratings. Designers should ensure the Output Enable signals to 3-state devices whose outputs are tied together are designed so there is no overlap.
LOGIC DIAGRAM
OE |
I0a |
I1a |
I0b |
I1b |
I0c |
I1c |
I0d |
I1d |
S |
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Za |
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Zb |
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Zc |
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Zd |
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Please note that this diagram is provided only for the understanding of logic operations and should not be used to estimate propagation delays.
FACT DATA
5-2
MC74AC257 MC74ACT257
MAXIMUM RATINGS*
Symbol |
Parameter |
Value |
Unit |
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VCC |
DC Supply Voltage (Referenced to GND) |
±0.5 to +7.0 |
V |
Vin |
DC Input Voltage (Referenced to GND) |
±0.5 to VCC +0.5 |
V |
Vout |
DC Output Voltage (Referenced to GND) |
±0.5 to VCC +0.5 |
V |
Iin |
DC Input Current, per Pin |
±20 |
mA |
Iout |
DC Output Sink/Source Current, per Pin |
±50 |
mA |
ICC |
DC VCC or GND Current per Output Pin |
±50 |
mA |
Tstg |
Storage Temperature |
±65 to +150 |
°C |
*Maximum Ratings are those values beyond which damage to the device may occur. Functional operation should be restricted to the Recommended Operating Conditions.
RECOMMENDED OPERATING CONDITIONS
Symbol |
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Typ |
Max |
Unit |
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VCC |
Supply Voltage |
′AC |
2.0 |
5.0 |
6.0 |
V |
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′ACT |
4.5 |
5.0 |
5.5 |
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Vin, Vout |
DC Input Voltage, Output Voltage (Ref. to GND) |
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0 |
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VCC |
V |
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Input Rise and Fall Time (Note 1) |
VCC @ 3.0 V |
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150 |
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tr, tf |
VCC @ 4.5 V |
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40 |
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ns/V |
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′AC Devices except Schmitt Inputs |
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VCC @ 5.5 V |
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25 |
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tr, tf |
Input Rise and Fall Time (Note 2) |
VCC @ 4.5 V |
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10 |
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ns/V |
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′ACT Devices except Schmitt Inputs |
VCC @ 5.5 V |
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8.0 |
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TJ |
Junction Temperature (PDIP) |
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140 |
°C |
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TA |
Operating Ambient Temperature Range |
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±40 |
25 |
85 |
°C |
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IOH |
Output Current Ð High |
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±24 |
mA |
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IOL |
Output Current Ð Low |
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24 |
mA |
1.Vin from 30% to 70% VCC; see individual Data Sheets for devices that differ from the typical input rise and fall times.
2.Vin from 0.8 V to 2.0 V; see individual Data Sheets for devices that differ from the typical input rise and fall times.
FACT DATA
5-3
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