74AC646 • 74ACT646 Octal Transceiver/Register with 3-STATE Outputs
November 1988
Revised October 2000
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 Figures 1, 2, 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:
Order Number
74AC646SC
74AC646SPC
74ACT646SC
74ACT646SPC
Package Number
M24B
N24C
M24B
N24C
Package Description
24-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-013, 0.300 Wide
24-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 Wide
24-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-013, 0.300 Wide
24-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
CPAB, CPBA
SAB, SBA
G
DIR
FACT is a trademark of Fairchild Semiconductor Corporation.
Description
Data Register A Inputs
Data Register A Outputs
Data Register B Inputs
Data Register B Outputs
Clock Pulse Inputs
Transmit/Receive Inputs
Output Enable Input
Direction Control Input
© 2000 Fairchild Semiconductor Corporation
DS010132
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74AC646 • 74ACT646
Function Table
Inputs
G
H
H
H
L
L
L
L
L
L
L
L
DIR
X
X
X
H
H
H
H
L
L
L
L
CPAB CPBA
H or L H or L
SAB
X
X
X
L
L
H
H
X
X
X
X
SBA
X
X
X
X
X
X
X
L
L
H
H
Output
Input
Input
Input
Input
Data I/O (Note 1)
Function
A
0
–A
7
B
0
–B
7
Isolation
Clock A
n
Data into A Register
Clock B
n
Data into B Register
A
n
to B
n
—Real Time (Transparent Mode)
Output Clock A
n
Data into A Register
A Register to B
n
(Stored Mode)
Clock A
n
Data into A Register and Output to B
n
B
n
to A
n
—Real Time (Transparent Mode)
Clock B
n
Data into B Register
B Register to A
n
(Stored Mode)
Clock B
n
Data into B Register and Output to A
n
X
X
X
X
X
X
H or L
X
X
X
X
X
H or L
H
=
HIGH Voltage Level
L
=
LOW Voltage Level
X
=
Immaterial
=
LOW-to-HIGH Transition
X
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
Real Time Transfer
B-Bus to A-Bus
FIGURE 1.
Storage from
Bus to Register
FIGURE 2.
Transfer from
Register to Bus
FIGURE 3.
FIGURE 4.
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74AC646 • 74ACT646
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.
3
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74AC646 • 74ACT646
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
−
0.5V to
+
7.0V
−
20 mA
+
20 mA
−
0.5V to V
CC
+
0.5V
−
20 mA
+
20 mA
−
0.5V to V
CC
+
0.5V
±
50 mA
±
50 mA
−
65
°
C to
+
150
°
C
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
OLD
I
OHD
I
CC
(Note 5)
I
OZT
Maximum Input Leakage Current
Minimum Dynamic
Output Current (Note 4)
Maximum Quiescent Supply Current
Maximum I/O
Leakage Current
5.5
±0.6
±6.0
µA
5.5
5.5
5.5
5.5
8.0
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
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
75
−75
80.0
µA
mA
mA
µA
V
I
OH
= 12 mA
I
OL
= 24 mA
I
OH
= 24 mA (Note 3)
V
I
=
V
CC
, GND
V
OLD
=
1.65V Max
V
OHD
=
3.85V Min
V
IN
=
V
CC
or GND
V
I
(OE)
=
V
IL
, V
IH
V
I
=
V
CC
, GND
V
O
=
V
CC
, GND
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
.
Units
Conditions
V
OUT
=
0.1V
V
or V
CC
−
0.1V
V
OUT
=
0.1V
V
or V
CC
−
0.1V
V
I
OUT
= −50 µA
I
OH
=
−12
mA
V
I
OH
=
−24
mA
I
OH
=
−24
mA (Note 3)
V
I
OUT
=
50
µA
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74AC646 • 74ACT646
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
CCT
I
OLD
I
OHD
I
CC
I
OZT
Maximum Input
Leakage Current
Maximum
I
CC
/Input
Minimum Dynamic
Output Current (Note 7)
Maximum Quiescent
Supply Current
Maximum I/O
Leakage Current
5.5
±0.6
±6.0
µA
5.5
5.5
5.5
5.5
5.5
8.0
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
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
1.5
75
−75
80.0
µA
mA
mA
mA
µA
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
−
2.1V
V
OLD
=
1.65V Max
V
OHD
=
3.85V Min
V
IN
=
V
CC
or GND
V
I
(OE)
=
V
IL
, V
IH
V
I
=
V
CC
, GND
V
O
=
V
CC
, 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.
5
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