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Motorola Semiconductors |
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8ĆBit Identity Comparator
The MC74AC521/74ACT521 is an expandable 8-bit comparator. It
compares two words of up to eight bits each and provides a LOW output when
the two words match bit for bit. The expansion input IA=B also serves as an
active LOW enable input.
• Compares Two 8-Bit Words in 6.5 ns Typ
• Expandable to Any Word Length
• 20-Pin Package
• Outputs Source/Sink 24 mA
• ′ACT521 has TTL-Compatible Inputs
VCC OA=B B7 A7 B6 A6 B5 A5 B4 A4
20 19 18 17 16 15 14 13 12 11
MC74AC521
MC74ACT521
8-BIT IDENTITY
COMPARATOR
N SUFFIX
CASE 738-03
PLASTIC
1 2 3 4 5 6 7 8 9 10
IA=B A0 B0 A1 B1 A2 B2 A3 B3 GND
DW SUFFIX
CASE 751D-04
PLASTIC
PIN NAMES
A0–A7
B0–B7
IA=B
OA=B
Word A Inputs
Word B Inputs
Expansion or Enable Input
Identity Output
TRUTH TABLE
Inputs
Outputs
IA=B
L
L
H
H
A, B
A = B*
A≠B
A = B*
A≠B
OA=B
L
H
H
H
H = HIGH Voltage Level
L = LOW Voltage Level
*A0=B0, A1=B1, A2=B2, etc.
LOGIC SYMBOL
B7 A7 B6 A6 B5 A5 B4 A4 B3 A3 B2 A2 B1 A1 B0 A0
IA=B
OA=B
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FACT DATA
5-1
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A0
B0
A1
B1
A2
B2
A3
B3
A4
B4
A5
B5
A6
B6
A7
B7
IA=B
MC74AC521 MC74ACT521
LOGIC DIAGRAM
Please note that this diagram is provided only for the understanding of logic
operations and should not be used to estimate propagation delays.
OA=B
MAXIMUM RATINGS*
Symbol
Parameter
Value
Unit
VCC
Vin
Vout
Iin
Iout
ICC
Tstg
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 Sink/Source Current, per Pin
DC VCC or GND Current per Output Pin
Storage Temperature
–0.5 to +7.0
–0.5 to VCC +0.5
–0.5 to VCC +0.5
±20
±50
±50
–65 to +150
V
V
V
mA
mA
mA
°C
* Maximum Ratings are those values beyond which damage to the device may occur. Functional operation should be restricted to the Recommended
Operating Conditions.
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FACT DATA
5-2
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