1999 Fairchild Semiconductor Corporation
DS009964
www.fairchildsemi.com
November 1988
Revised November 1999
7
4
AC
5
21
74ACT521 8-Bi
t Ident
i
t
y Com
p
ar
ator
74AC521 74ACT521
8-Bit Identity Comparator
General Description
The AC/ACT521 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 I
A
=
B
also serves as an active LOW enable
input.
Features
s
I
CC
reduced by 50%
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
ACT521 has TTL-compatible inputs
Ordering Code:
Device also available in Tape and Reel. Specify by appending suffix letter "X" to the ordering table.
Logic Symbols
IEEE/IEC
Connection Diagram
Pin Descriptions
FACT
is a trademark of Fairchild Semiconductor Corporation.
Order Number
Package Number
Package Description
74AC521SC
M20B
20-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-013, 0.300" Wide Body
74AC521SJ
M20D
20-Lead Small Outline Package (SOP), EIAJ TYPE II, 5.3mm Wide
74AC521PC
N20A
20-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300" Wide
74ACT521SC
M20B
20-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-013, 0.300" Wide Body
74ACT521SJ
M20D
20-Lead Small Outline Package (SOP), EIAJ TYPE II, 5.3mm Wide
74ACT521PC
N20A
20-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300" Wide
Pin Names
Description
A
0
A
7
Word A Inputs
B
0
B
7
Word B Inputs
T
A
=
B
Expansion or Enable Input
O
A
=
B
Identity Output
www.fairchildsemi.com
2
74AC521
74ACT521
Truth Table
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
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
Inputs
Outputs
I
A
=
B
A, B
O
A
=
B
L
A
=
B (Note 1)
L
L
A
H
H
A
=
B (Note 1)
H
H
A
H
3
www.fairchildsemi.com
74
A
C
52
1
74ACT521
Absolute Maximum Ratings
(Note 2)
Recommended Operating
Conditions
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, output/input loading variables. Fairchild does not rec-
ommend operation of FACT
circuits outside databook specifications.
DC Electrical Characteristics for AC
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
.
Supply Voltage (V
CC
)
-
0.5V to
+
7.0V
DC Input Diode Current (I
IK
)
V
I
=
-
0.5V
-
20 mA
V
I
=
V
CC
+
0.5V
+
20 mA
DC Input Voltage (V
I
)
-
0.5V to V
CC
+
0.5V
DC Output Diode Current (I
OK
)
V
O
=
-
0.5V
-
20 mA
V
O
=
V
CC
+
0.5V
+
20 mA
DC Output Voltage (V
O
)
-
0.5V to V
CC
+
0.5V
DC Output Source
or Sink Current (I
O
)
50 mA
DC V
CC
or Ground Current
per Output Pin (I
CC
or I
GND
)
50 mA
Storage Temperature (T
STG
)
-
65
C to
+
150
C
Junction Temperature (T
J
)
PDIP
140
C
Supply Voltage (V
CC
)
AC
2.0V to 6.0V
ACT
4.5V to 5.5V
Input Voltage (V
I
)
0V to V
CC
Output Voltage (V
O
)
0V to V
CC
Operating Temperature (T
A
)
-
40
C to
+
85
C
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
125 mV/ns
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
Symbol
Parameter
V
CC
T
A
=
+
25
C
T
A
=
-
40
C to
+
85
C
Units
Conditions
(V)
Typ
Guaranteed Limits
V
IH
Minimum HIGH Level
3.0
1.5
2.1
2.1
V
OUT
=
0.1V
Input Voltage
4.5
2.25
3.15
3.15
V
or V
CC
-
0.1V
5.5
2.75
3.85
3.85
V
IL
Maximum LOW Level
3.0
1.5
0.9
0.9
V
OUT
=
0.1V
Input Voltage
4.5
2.25
1.35
1.35
V
or V
CC
-
0.1V
5.5
2.75
1.65
1.65
V
OH
Minimum HIGH Level
3.0
2.99
2.9
2.9
Output Voltage
4.5
4.49
4.4
4.4
V
I
OUT
=
-
50
A
5.5
5.49
5.4
5.4
V
IN
=
V
IL
or V
IH
3.0
2.56
2.46
I
OH
=
-
12 mA
4.5
3.86
3.76
V
I
OH
=
-
24 mA
5.5
4.86
4.76
I
OH
=
-
24 mA (Note 3)
V
OL
Maximum LOW Level
3.0
0.002
0.1
0.1
Output Voltage
4.5
0.001
0.1
0.1
V
I
OUT
=
50
A
5.5
0.001
0.1
0.1
V
IN
=
V
IL
or V
IH
3.0
0.36
0.44
I
OL
= 12 mA
4.5
0.36
0.44
V
I
OL
= 24 mA
5.5
0.36
0.44
I
OL
= 24 mA (Note 3)
I
IN
Maximum Input
5.5
0.1
1.0
A
V
I
=
V
CC
, GND
(Note 5)
Leakage Current
I
OLD
Minimum Dynamic
5.5
75
mA
V
OLD
=
1.65V Max
I
OHD
Output Current (Note 4)
5.5
-
75
mA
V
OHD
=
3.85V Min
I
CC
Maximum Quiescent
5.5
4.0
40.0
A
V
IN
=
V
CC
(Note 5)
Supply Current
or GND
www.fairchildsemi.com
4
74AC521
74ACT521
DC Electrical Characteristics for ACT
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.
AC Electrical Characteristics for AC
Note 8: Voltage Range 3.3 is 3.3V
0.3V
Voltage Range 5.0 is 5.0V
0.5V
Symbol Parameter
V
CC
T
A
=
+
25
C
T
A
=
-
40
C to
+
85
C
Units
Conditions
(V)
Typ
Guaranteed Limits
V
IH
Minimum HIGH Level
4.5
1.5
2.0
2.0
V
V
OUT
=
0.1V
Input Voltage
5.5
1.5
2.0
2.0
or V
CC
-
0.1V
V
IL
Maximum LOW Level
4.5
1.5
0.8
0.8
V
V
OUT
=
0.1V
Input Voltage
5.5
1.5
0.8
0.8
or V
CC
-
0.1V
V
OH
Minimum HIGH Level
4.5
4.49
4.4
4.4
V
I
OUT
=
-
50
A
Output Voltage
5.5
5.49
5.4
5.4
V
IN
=
V
IL
or V
IH
4.5
3.86
3.76
V
I
OH
=
-
24 mA
5.5
4.86
4.76
I
OH
=
-
24 mA (Note 6)
V
OL
Maximum LOW Level
4.5
0.001
0.1
0.1
V
I
OUT
=
50
A
Output Voltage
5.5
0.001
0.1
0.1
V
IN
=
V
IL
or V
IH
4.5
0.36
0.44
V
I
OL
= 24 mA
5.5
0.36
0.44
I
OL
= 24 mA (Note 6)
I
IN
Maximum Input
5.5
0.1
1.0
A
V
I
=
V
CC
, GND
Leakage Current
I
CCT
Maximum
5.5
0.6
1.5
mA
V
I
=
V
CC
-
2.1V
I
CC
/Input
I
OLD
Minimum Dynamic
5.5
75
mA
V
OLD
=
1.65V Max
I
OHD
Output Current (Note 7)
5.5
-
75
mA
V
OHD
=
3.85V Min
I
CC
Maximum Quiescent
5.5
4.0
40.0
A
V
IN
=
V
CC
Supply Current
or GND
V
CC
T
A
=
+
25
C
T
A
=
-
40
C to
+
85
C
Symbol
Parameter
(V)
C
L
=
50 pF
C
L
=
50 pF
Units
(Note 8)
Min
Typ
Max
Min
Max
t
PLH
Propagation Delay
3.3
3.5
7.0
11.0
3.0
12.0
ns
A
n
or B
n
to O
A
=
B
5.0
2.5
5.0
8.0
2.0
9.0
t
PHL
Propagation Delay
3.3
4.5
7.5
11.5
3.5
12.5
ns
A
n
or B
n
to O
A
=
B
5.0
3.0
5.5
8.5
2.5
9.0
t
PLH
Propagation Delay
3.3
3.0
5.5
8.0
2.5
9.0
ns
I
A
=
B
to O
A
=
B
5.0
2.5
4.0
6.0
2.0
7.0
t
PHL
Propagation Delay
3.3
3.0
5.5
8.0
2.5
9.0
ns
I
A
=
B
to O
A
=
B
5.0
2.0
4.0
6.0
2.0
7.0
5
www.fairchildsemi.com
74
A
C
52
1
74ACT521
AC Electrical Characteristics for ACT
Note 9: Voltage Range 5.0 is 5.0V
0.5V
Capacitance
V
CC
T
A
=
+
25
C
T
A
=
-
40
C to
+
85
C
Symbol
Parameter
(V)
C
L
=
50 pF
C
L
=
50 pF
Units
(Note 9)
Min
Typ
Max
Min
Max
t
PLH
Propagation Delay
5.0
3.0
5.5
9.0
2.5
9.5
ns
A
n
or B
n
to O
A
=
B
t
PHL
Propagation Delay
5.0
3.0
6.0
10.0
2.5
11.0
ns
A
n
or B
n
to O
A
=
B
t
PLH
Propagation Delay
5.0
2.0
4.0
6.5
2.0
7.0
ns
I
A
=
B
to O
A
=
B
t
PHL
Propagation Delay
5.0
2.5
5.0
7.5
2.0
8.0
ns
I
A
=
B
to O
A
=
B
Symbol
Parameter
Typ
Units
Conditions
C
IN
Input Capacitance
4.5
pF
V
CC
=
OPEN
C
PD
Power Dissipation Capacitance
40
pF
V
CC
=
5.0V
www.fairchildsemi.com
6
74AC521
74ACT521
Physical Dimensions
inches (millimeters) unless otherwise noted
20-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-013, 0.300" Wide Body
Package Number M20B
7
www.fairchildsemi.com
74
A
C
52
1
74ACT521
Physical Dimensions
inches (millimeters) unless otherwise noted (Continued)
20-Lead Small Outline Package (SOP), EIAJ TYPE II, 5.3mm Wide
Package Number M20D
www.fairchildsemi.com
8
74AC521
7
4
AC
T
521 8-
Bit
I
dent
it
y Compar
ator
Physical Dimensions
inches (millimeters) unless otherwise noted (Continued)
20-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300" Wide
Package Number N20A
Fairchild does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and
Fairchild reserves the right at any time without notice to change said circuitry and specifications.
LIFE SUPPORT POLICY
FAIRCHILD'S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT
DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF FAIRCHILD
SEMICONDUCTOR CORPORATION. As used herein:
1. Life support devices or systems are devices or systems
which, (a) are intended for surgical implant into the
body, or (b) support or sustain life, and (c) whose failure
to perform when properly used in accordance with
instructions for use provided in the labeling, can be rea-
sonably expected to result in a significant injury to the
user.
2. A critical component in any component of a life support
device or system whose failure to perform can be rea-
sonably expected to cause the failure of the life support
device or system, or to affect its safety or effectiveness.
www.fairchildsemi.com
PDF 
ZIP