November 1988
Revised December 1998
7
4
A
C
646
·
7
4
A
C
T646 Octal
T
r
ans
ceiver
/Regi
st
er w
i
th
3-
ST
A
T
E O
u
t
put
s
© 1999 Fairchild Semiconductor Corporation
DS010132.prf
www.fairchildsemi.com
74AC646 · 74ACT646
Octal Transceiver/Register with 3-STATE Outputs
General Description
The AC/ACT646 consist of registered bus transceiver cir-
cuits, with outputs, D-type flip-flops and control circuitry
providing multiplexed transmission of data directly from the
input bus or from the internal storage registers. Data on the
A or B bus will be loaded into the respective registers on
the LOW-to-HIGH transition of the appropriate clock pin
(CPAB or CPBA). The four fundamental data handling
functions available are illustrated in Figure 1, Figure 2, Fig-
ure 3, and Figure 4.
Features
s
Independent registers for A and B buses
s
Multiplexed real-time and stored data transfers
s
3-STATE outputs
s
300 mil dual-in-line package
s
Outputs source/sink 24 mA
s
ACT646 has TTL compatible inputs
Ordering Code:
Device also available in Tape and Reel. Specify by appending suffix letter "X" to the ordering code.
Logic Symbols
IEEE/IEC
Connection Diagram
Pin Assignment
for DIP and SOIC
Pin Descriptions
FACT
TM
is a trademark of Fairchild Semiconductor Corporation.
Order Number
Package Number
Package Description
74AC646SC
M24B
24-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-013, 0.300" Wide Body
74AC646SPC
N24C
24-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-100, 0.300" Wide
74ACT646SPC
N24C
24-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-100, 0.300" Wide
Pin Names
Description
A
0
A
7
Data Register A Inputs
Data Register A Outputs
B
0
B
7
Data Register B Inputs
Data Register B Outputs
CPAB, CPBA
Clock Pulse Inputs
SAB, SBA
Transmit/Receive Inputs
G
Output Enable Input
DIR
Direction Control Input
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2
74A
C646
· 74A
CT646
Function Table
H
=
HIGH Voltage Level
L
=
LOW Voltage Level
X
=
Immaterial
=
LOW-to-HIGH Transition
Note 1: The data output functions may be enabled or disabled by various signals at the G and DIR inputs. Data input functions are always enabled; i.e., data
at the bus pins will be stored on every LOW-to-HIGH transition of the appropriate clock inputs.
Real Time Transfer
A-Bus to B-Bus
FIGURE 1.
Real Time Transfer
B-Bus to A-Bus
FIGURE 2.
Storage from
Bus to Register
FIGURE 3.
Transfer from
Register to Bus
FIGURE 4.
Inputs
Data I/O (Note 1)
Function
G
DIR
CPAB CPBA
SAB
SBA
A
0
A
7
B
0
B
7
H
X
H or L
H or
L
X
X
Isolation
H
X
X
X
X
Input
Input
Clock A
n
Data into A Register
H
X
X
X
X
Clock B
n
Data into B Register
L
H
X
X
L
X
A
n
to B
n
--Real Time (Transparent Mode)
L
H
X
L
X
Input
Output
Clock A
n
Data into A Register
L
H
H or L
X
H
X
A Register to B
n
(Stored Mode)
L
H
X
H
X
Clock A
n
Data into A Register and Output to B
n
L
L
X
X
X
L
B
n
to A
n
--Real Time (Transparent Mode)
L
L
X
X
L
Output
Input
Clock B
n
Data into B Register
L
L
X
H or L
X
H
B Register to A
n
(Stored Mode)
L
L
X
X
H
Clock B
n
Data into B Register and Output to A
n
3
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7
4
A
C
646
· 7
4
A
C
T646
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.
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4
74A
C646
· 74A
CT646
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, and output/input loading variables. Fairchild does not
recommend operation of FACT
TM
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
I
OUT
=
-
50
µ
A
Output Voltage
4.5
4.49
4.4
4.4
V
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
I
OUT
=
50
µ
A
Output Voltage
4.5
0.001
0.1
0.1
V
5.5
0.001
0.1
0.1
V
IN
=
V
IL
or V
IH
3.0
0.36
0.44
I
OH
= 12 mA
4.5
0.36
0.44
V
I
OL
= 24 mA
5.5
0.36
0.44
I
OH
= 24 mA (Note 3)
I
IN
(Note 5)
Maximum Input Leakage Current
5.5
±
0.1
±
1.0
µ
A
V
I
=
V
CC
, GND
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
(Note 5)
Maximum Quiescent Supply Current
5.5
8.0
80.0
µ
A
V
IN
=
V
CC
or GND
I
OZT
Maximum I/O
V
I
(OE)
=
V
IL
, V
IH
Leakage Current
5.5
±
0.6
±
6.0
µ
A
V
I
=
V
CC
, GND
V
O
=
V
CC
, GND
5
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7
4
A
C
646
· 7
4
A
C
T646
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
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
µ
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
µ
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)
Maximum Input
Leakage Current
5.5
±
0.1
±
1.0
µ
A
V
I
=
V
CC
, GND
Maximum
I
CC
/Input
5.5
0.6
1.5
mA
V
I
=
V
CC
-
2.1V
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
8.0
80.0
µ
A
V
IN
=
V
CC
Supply Current
or GND
I
OZT
Maximum I/O
V
I
(OE)
=
V
IL
, V
IH
Leakage Current
5.5
±
0.6
±
6.0
µ
A
V
I
=
V
CC
, GND
V
O
=
V
CC
, 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
4.0
10.5
16.5
3.0
18.5
ns
Clock to Bus
5.0
2.5
7.5
12.0
2.0
13.0
t
PHL
Propagation Delay
3.3
3.0
9.5
14.5
2.5
16.0
ns
Clock to Bus
5.0
2.0
6.5
10.5
1.5
11.5
t
PLH
Propagation Delay
3.3
2.5
7.5
12.0
2.0
13.5
ns
Bus to Bus
5.0
1.5
5.0
8.0
1.0
9.0
t
PHL
Propagation Delay
3.3
1.5
7.5
12.5
1.5
13.5
ns
Bus to Bus
5.0
1.5
5.0
9.0
1.0
9.5
t
PLH
Propagation Delay
3.3
2.0
8.5
13.5
1.5
15.5
SBA or SAB to A
n
or B
n
5.0
1.5
6.0
10.0
1.5
11.0
ns
(w/ A
n
or B
n
HIGH or LOW)
t
PHL
Propagation Delay
3.3
1.5
8.5
13.5
1.5
15.0
SBA or SAB to A
n
or B
n
5.0
1.5
6.0
10.0
1.5
11.0
ns
(w/ A
n
or B
n
HIGH or LOW)
t
PZH
Enable Time
3.3
2.5
7.0
11.5
2.0
12.5
ns
G to A
n
or B
n
5.0
1.5
5.0
8.5
1.5
9.0
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6
74A
C646
· 74A
CT646
AC Electrical Characteristics for AC
(Continued)
Note 8: Voltage Range 3.3 is 3.3V
±
0.3V
Voltage Range 5.0 is 5.0V
±
0.5V
AC Operating Requirements for AC
Note 9: Voltage Range 3.3 is 3.3V
±
0.3V
Voltage Range 5.0 is 5.0V
±
0.5V
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
PZL
Enable Time
3.3
2.5
7.5
12.5
2.0
14.0
ns
G to A
n
or B
n
5.0
1.5
5.5
9.0
1.5
10.0
t
PHZ
Disable Time
3.3
3.0
8.0
12.5
2.5
13.5
ns
G to A
n
or B
n
5.0
2.0
6.5
10.0
2.0
11.0
t
PLZ
Disable Time
3.3
2.0
7.5
12.0
2.0
13.5
ns
G to A
n
or B
n
5.0
1.5
6.0
9.5
1.5
10.5
t
PZH
Enable Time
3.3
2.0
6.5
11.0
1.5
12.0
ns
DIR to A
n
or B
n
5.0
1.5
5.0
7.5
1.0
8.5
t
PZL
Enable Time
3.3
2.5
7.0
11.5
2.0
13.0
ns
DIR to A
n
or B
n
5.0
1.5
5.0
8.0
1.0
9.0
t
PHZ
Disable Time
3.3
2.5
7.5
11.5
1.5
12.5
ns
DIR to A
n
or B
n
5.0
1.5
5.5
9.5
1.5
10.0
t
PLZ
Disable Time
3.3
1.5
7.5
12.0
1.5
13.5
ns
DIR to A
n
or B
n
5.0
1.5
5.5
9.5
1.5
10.5
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)
Typ
Guaranteed Minimum
t
S
Setup Time, HIGH or LOW
3.3
2.0
5.0
5.5
ns
Bus to Clock
5.0
1.5
4.0
4.5
t
H
Hold Time, HIGH or LOW
3.3
-
1.5
0
0
ns
Bus to Clock
5.0
-
0.5
0.5
1.0
t
W
Clock Pulse Width
3.3
2.0
3.5
4.5
ns
HIGH or LOW
5.0
2.0
3.5
3.5
7
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7
4
A
C
646
· 7
4
A
C
T646
AC Electrical Characteristics for ACT
Note 10: Voltage Range 5.0 is 5.0V
±
0.5V
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 10)
Min
Typ
Max
Min
Max
t
PLH
Propagation Delay
5.0
3.5
12.0
14.5
3.0
16.0
ns
Clock to Bus
t
PHL
Propagation Delay
5.0
4.0
12.0
14.5
3.5
16.0
ns
Clock to Bus
t
PLH
Propagation Delay
5.0
3.0
8.5
10.5
2.5
11.5
ns
Bus to Bus
t
PHL
Propagation Delay
5.0
2.5
8.5
10.5
2.0
11.5
ns
Bus to Bus
t
PLH
Propagation Delay
SBA or SAB to A
n
to B
n
5.0
3.0
9.5
11.5
2.5
12.5
ns
(w/A
n
or B
n
HIGH or LOW)
t
PHL
Propagation Delay
SBA or SAB to A
n
to B
n
5.0
3.0
9.5
11.5
2.5
12.5
ns
(w/A
n
or B
n
HIGH or LOW)
t
PZH
Enable Time
5.0
2.0
9.0
11.0
1.5
12.0
ns
G to A
n
or B
n
t
PZL
Enable Time
5.0
3.5
9.0
11.0
3.0
12.0
ns
G to A
n
or B
n
t
PHZ
Disable Time
5.0
5.0
10.5
13.0
4.5
14.5
ns
G to A
n
or B
n
t
PLZ
Disable Time
5.0
3.5
10.0
12.5
3.0
14.0
ns
G to A
n
or B
n
t
PZH
Enable Time
5.0
2.0
6.5
10.5
1.5
11.5
ns
DIR to A
n
or B
n
t
PZL
Enable Time
5.0
3.5
6.5
10.5
3.0
11.5
ns
DIR to A
n
or B
n
t
PHZ
Disable Time
5.0
5.0
8.5
12.5
4.5
13.5
ns
DIR to A
n
or B
n
t
PLZ
Disable Time
5.0
3.5
8.5
12.5
3.0
13.5
ns
DIR to A
n
or B
n
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8
74A
C646
· 74A
CT646
AC Operating Requirements for ACT
Note 11: 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 11)
Typ
Guaranteed Minimum
t
S
Setup Time, HIGH or LOW
5.0
2.5
7.0
8.0
ns
BUS to Clock
t
H
Hold Time, HIGH or LOW
5.0
0
2.5
2.5
ns
Bus to Clock
t
W
Clock Pulse Width
5.0
4.5
7.0
8.0
ns
HIGH or LOW
Symbol
Parameter
Typ
Units
Conditions
C
IN
Input Capacitance
4.5
pF
V
CC
=
OPEN
C
I/O
Input/Output Capacitance
15.0
pF
V
CC
=
5.0V
C
PD
Power Dissipation Capacitance
60.0
pF
V
CC
=
5.0V
9
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7
4
A
C
646
· 7
4
A
C
T646
Physical Dimensions
inches (millimeters) unless otherwise noted
24-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-013, 0.300" Wide Body
Package Number M24B
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.
74
A
C
646
·
74
A
C
T646 Octal
T
r
ansc
eiver
/Regi
st
er w
i
th 3-
ST
A
T
E O
u
t
puts
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
Physical Dimensions
inches (millimeters) unless otherwise noted (Continued)
24-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-100, 0.300" Wide
Package Number N24C
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