74AC520 • 74ACT520 8-Bit Identity Comparator
February 1989
Revised November 1999
74AC520 • 74ACT520
8-Bit Identity Comparator
General Description
The AC/ACT520 are expandable 8-bit comparators. They
compare two words of up to eight bits each and provide a
LOW output when the two words match bit for bit. The
expansion input I
A
=
B
also serves as an active LOW enable
input.
Features
s
Compares two 8-bit words in 6.5 ns typ
s
Expandable to any word length
s
20-pin package
s
Outputs source/sink 24 mA
s
ACT520 has TTL-compatible inputs
Ordering Code:
Order Number
74AC520SC
74AC520PC
74ACT520SC
74ACT520SJ
74ACT520PC
Package Number
M20B
N20A
M20B
M20D
N20A
Package Description
20-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-013, 0.300” Wide Body
20-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300” Wide
20-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-013, 0.300” Wide Body
20-Lead Small Outline Package (SOP), EIAJ TYPE II, 5.3mm Wide
20-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300” Wide
Device also available in Tape and Reel. Specify by appending suffix letter “X” to the ordering code.
Logic Symbols
Connection Diagram
IEEE/IEC
Pin Descriptions
Pin Names
A
0
–A
7
B
0
–B
7
T
A
=
B
O
A
=
B
Description
Word A Inputs
Word B Inputs
Expansion or Enable Input
Identity Output
FACT is a trademark of Fairchild Semiconductor Corporation.
© 1999 Fairchild Semiconductor Corporation
DS010194
www.fairchildsemi.com
74AC520 • 74ACT520
Truth Table
Inputs
I
A
=
B
L
L
H
H
H
=
HIGH Voltage Level
L
=
LOW Voltage Level
Note 1:
*A
0
=
B
0
, A
1
=
B
1
, A
2
=
B
2
, etc.
Logic Diagram
Outputs
O
A
=
B
L
H
H
H
A, B
A
=
B (Note 1)
A
≠Β
A
=
B (Note 1)
A
≠Β
Please note that this diagram is provided only for the understanding of logic
operations and should not be used to estimate propagation delays.
Applications
Ripple Expansion
Parallel Expansion
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2
74AC520 • 74ACT520
Absolute Maximum Ratings
(Note 2)
Supply Voltage (V
CC
)
DC Input Diode Current (I
IK
)
V
I
= −0.5V
V
I
=
V
CC
+
0.5V
DC Input Voltage (V
I
)
DC Output Diode Current (I
OK
)
V
O
= −0.5V
V
O
=
V
CC
+
0.5V
DC Output Voltage (V
O
)
DC Output Source
or Sink Current (I
O
)
DC V
CC
or Ground Current
per Output Pin (I
CC
or I
GND
)
Storage Temperature (T
STG
)
Junction Temperature (T
J
)
PDIP
140°C
±50
mA
−65°C
to
+150°C
±50
mA
−20
mA
+20
mA
−0.5V
to V
CC
+
0.5V
−20
mA
+20
mA
−0.5V
to V
CC
+
0.5V
−0.5V
to
+7.0V
Recommended Operating
Conditions
Supply Voltage (V
CC
)
AC
ACT
Input Voltage (V
I
)
Output Voltage (V
O
)
Operating Temperature (T
A
)
Minimum Input Edge Rate (∆V/∆t)
AC Devices
V
IN
from 30% to 70% of V
CC
V
CC
@ 3.3V, 4.5V, 5.5V
Minimum Input Edge Rate (∆V/∆t)
ACT Devices
V
IN
from 0.8V to 2.0V
V
CC
@ 4.5V, 5.5V
125 mV/ns
Note 2:
Absolute maximum ratings are those values beyond which damage
to the device may occur. The databook specifications should be met, with-
out exception, to ensure that the system design is reliable over its power
supply, temperature, and output/input loading variables. Fairchild does not
recommend operation of FACT circuits outside databook specifications.
2.0V to 6.0V
4.5V to 5.5V
0V to V
CC
0V to V
CC
−40°C
to
+85°C
125 mV/ns
DC Electrical Characteristics for AC
Symbol
V
IH
Parameter
Minimum HIGH Level
Input Voltage
V
IL
Maximum LOW Level
Input Voltage
V
OH
Minimum HIGH Level
Output Voltage
V
CC
(V)
3.0
4.5
5.5
3.0
4.5
5.5
3.0
4.5
5.5
3.0
4.5
5.5
V
OL
Maximum LOW Level
Output Voltage
3.0
4.5
5.5
3.0
4.5
5.5
I
IN
(Note 5)
I
IH
I
IL
I
OLD
I
OHD
I
CC
Maximum Input Leakage Current
Maximum Input HIGH Leakage Current
Maximum Input LOW Leakage Current
Minimum Dynamic
Output Current (Note 4)
Maximum Quiescent Supply Current
5.5
5.5
5.5
5.5
5.5
5.5
5.5
2.3
4.0
4.8
−0.3
0.002
0.001
0.001
T
A
= +25°C
Typ
1.5
2.25
2.75
1.5
2.25
2.75
2.99
4.49
5.49
2.1
3.15
3.85
0.9
1.35
1.65
2.9
4.4
5.4
2.56
3.86
4.86
0.1
0.1
0.1
0.36
0.36
0.36
±0.1
10.0
−0.6
T
A
= −40°C
to
+85°C
Guaranteed Limits
2.1
3.15
3.85
0.9
1.35
1.65
2.9
4.4
5.4
V
IN
=
V
IL
or V
IH
2.46
3.76
4.76
0.1
0.1
0.1
V
IN
=
V
IL
or V
IH
0.44
0.44
0.44
±1.0
10.0
−1.0
75
−75
40.0
8.0
µA
µA
mA
mA
mA
µA
mA
V
I
OL
= 12 mA
I
OL
= 24 mA
I
OL
= 24 mA (Note 3)
V
I
=
V
CC
, GND, A Inputs Only
V
I
=
V
CC
, B Inputs Only
V
I
=
V
CC
, B Inputs Only
V
OLD
=
1.65V Max
V
OHD
=
3.85V Min
V
IN
=
V
CC
V
IN
=
GND
V
I
OUT
=
50
µA
V
I
OH
=
−12
mA
I
OH
=
−24
mA
I
OH
=
−24
mA (Note 3)
V
I
OUT
= −50 µA
V
V
OUT
=
0.1V
or V
CC
−
0.1V
V
Units
Conditions
V
OUT
=
0.1V
or V
CC
−
0.1V
I
CC
(Note 5) Maximum Quiescent Supply Current
Note 3:
All outputs loaded; thresholds on input associated with output under test.
Note 4:
Maximum test duration 2.0 ms, one output loaded at a time.
Note 5:
I
IN
and I
CC
@ 3.0V are guaranteed to be less than or equal to the respective limit @ 5.5V V
CC
.
3
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74AC520 • 74ACT520
DC Electrical Characteristics for ACT
Symbol
V
IH
V
IL
V
OH
Parameter
Minimum HIGH Level
Input Voltage
Maximum LOW Level
Input Voltage
Minimum HIGH Level
Output Voltage
V
CC
(V)
4.5
5.5
4.5
5.5
4.5
5.5
4.5
5.5
V
OL
Maximum LOW Level
Output Voltage
4.5
5.5
4.5
5.5
I
IN
I
IH
I
IL
I
CCT
I
OLD
I
OHD
I
CC
I
CC
Maximum Input
Leakage Current
Maximum Input
HIGH Leakage Current
Maximum Input
LOW Leakage Current
Maximum
I
CC
/Input
Minimum Dynamic
Output Current (Note 7)
Maximum Quiescent
Supply Current
Maximum Quiescent
Supply Current
5.5
5.5
5.5
5.5
5.5
5.5
5.5
5.5
2.3
4.0
4.8
−0.3
0.6
0.001
0.001
T
A
= +25°C
Typ
1.5
1.5
1.5
1.5
4.49
5.49
2.0
2.0
0.8
0.8
4.4
5.4
3.86
4.86
0.1
0.1
0.36
0.36
±0.1
10.0
−0.6
T
A
= −40°C
to
+85°C
Guaranteed Limits
2.0
2.0
0.8
0.8
4.4
5.4
3.76
4.76
0.1
0.1
0.44
0.44
±1.0
10.0
−1.0
1.5
75
−75
40.0
8.0
µA
µA
mA
mA
mA
mA
µA
mA
V
Units
V
V
V
Conditions
V
OUT
=
0.1V
or V
CC
−
0.1V
V
OUT
=
0.1V
or V
CC
−
0.1V
I
OUT
= −50 µA
V
IN
=
V
IL
or V
IH
V
I
OH
= −24
mA
I
OH
= −24
mA (Note 6)
I
OUT
=
50
µA
V
IN
=
V
IL
or V
IH
V
I
OL
= 24 mA
I
OL
= 24 mA (Note 6)
V
I
=
V
CC
, GND
V
I
=
V
CC
B Inputs Only
V
I
=
V
CC
B Inputs Only
V
I
=
V
CC
−
2.1V
V
OLD
=
1.65V Max
V
OHD
=
3.85V Min
V
IN
=
V
CC
or GND
V
IN
=
GND
Note 6:
All outputs loaded; thresholds on input associated with output under test.
Note 7:
Maximum test duration 2.0 ms, one output loaded at a time.
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4
74AC520 • 74ACT520
AC Electrical Characteristics for AC
V
CC
Symbol
t
PLH
t
PHL
t
PLH
t
PHL
Parameter
Propagation Delay
A
n
or B
n
to O
A
=
B
Propagation Delay
A
n
or B
n
to O
A
=
B
Propagation Delay
I
A
=
B
to O
A
=
B
Propagation Delay
I
A
=
B
to O
A
=
B
Note 8:
Voltage Range 3.3 is 3.3V
±
0.3V
Voltage Range 5.0 is 5.0V
±
0.5V
T
A
= +25°C
C
L
=
50 pF
Min
4.0
2.5
4.5
3.0
3.5
2.5
3.5
2.5
Typ
7.5
5.5
8.0
5.5
5.5
4.5
5.5
4.5
Max
11.5
8.5
12.0
9.0
8.5
6.5
8.5
6.5
T
A
= −40°C
to
+85°C
C
L
=
50 pF
Min
3.0
2.0
3.5
2.5
2.5
2.0
2.5
2.0
Max
13.0
9.5
13.5
10.0
9.5
7.0
9.5
7.0
ns
ns
ns
ns
Units
(V)
(Note 8)
3.3
5.0
3.3
5.0
3.3
5.0
3.3
5.0
AC Electrical Characteristics for ACT
V
CC
Symbol
t
PLH
t
PHL
t
PLH
t
PHL
Parameter
Propagation Delay
A
n
or B
n
to O
A
=
B
Propagation Delay
A
n
or B
n
to O
A
=
B
Propagation Delay
I
A
=
B
to O
A
=
B
Propagation Delay
I
A
=
B
to O
A
=
B
Note 9:
Voltage Range 5.0 is 5.0V
±
0.5V
T
A
= +25°C
C
L
=
50 pF
Min
3.0
3.0
2.0
2.5
Typ
5.5
6.0
4.0
5.0
Max
8.5
10.0
6.0
7.5
T
A
= −40°C
to
+85°C
C
L
=
50 pF
Min
2.5
2.5
2.0
2.0
Max
9.5
11.5
6.5
8.5
ns
ns
ns
ns
Units
(V)
(Note 9)
5.0
5.0
5.0
5.0
Capacitance
Symbol
C
IN
C
PD
Parameter
Input Capacitance
Power Dissipation Capacitance
Typ
4.5
40
Units
pF
pF
V
CC
=
OPEN
V
CC
=
5.0V
Conditions
5
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