1999 Fairchild Semiconductor Corporation
DS010629
www.fairchildsemi.com
November 1989
Revised August 1999
7
4F2645 O
c
t
a
l
Bus T
r
ansc
eiver
74F2645
Octal Bus Transceiver
with 25
Series Resistors in the Outputs
General Description
This device is an octal bus transceiver designed for asyn-
chronous two-way data flow between the A and B busses
and is functionally equivalent to the 74F645. The 25
series resistors in the outputs reduce ringing and eliminate
the need for external resistors. Both busses are capable of
sinking 12 mA, sourcing 15 mA, have 3-STATE outputs,
and a common output enable pin. The direction of data flow
is determined by the transmit/receive (T/R) input. The
74F2645 is a low power version of the 74F245 with 25
series resistors in the outputs.
Features
s
25
series resistors in the outputs eliminates the need
for external resistors
s
Designed for asynchronous two-way data flow between
busses
s
Outputs sink 12 mA and source 15 mA
s
Transmit/receive (T/R) input controls the direction of
data flow
s
74F2645 is a low power version of the 74F245 with 25
series resistors in the outputs
Ordering Code:
Devices also available in Tape and Reel. Specify by appending the suffix letter "X" to the ordering code.
Logic Symbol
Connection Diagram
FAST
is a registered trademark of Fairchild Semiconductor Corporation.
Order Number
Package Number
Package Description
74F2645SC
M20B
20-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-013, 0.300 Wide
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2
74F2645
Unit Loading/Fan Out
Functional Description
The output enable (OE) is active LOW. If the device is dis-
abled (OE HIGH), the outputs are in the high impedance
state. The transmit/receive input (T/R) controls whether
data is transmitted from the A bus to the B bus or from the
B bus to the A bus. When T/R is LOW, B data is sent to the
A bus. If T/R is HIGH, A data is sent to the B bus.
Function Table
H
=
HIGH Voltage Level
L
=
LOW Voltage Level
X
=
Don't Care
Z
=
High Impedance State
Logic Diagram
Pin Names
Description
U.L.
Input I
IH
/I
IL
HIGH/LOW
Output I
OH
/I
OL
OE
Output Enable Input (Active LOW)
1.0/1.0
20
A/
-
0.6 mA
T/R
Transmit/Receive Input
1.0/1.0
20
A/
-
0.6 mA
A
0
A
7
Side A Inputs or
3.5/0.667
70
A/
-
0.4 mA
3-STATE Outputs
750/20
-
15 mA/12 mA
B
0
B
7
Side B Inputs or
3.5/0.667
70
A/
-
0.4 mA
3-STATE Outputs
750/20
-
15 mA/12 mA
Inputs
Outputs
OE
T/R
L
L
Bus B data to Bus A
L
H
Bus A data to Bus B
H
X
Z
3
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7
4F2645
Absolute Maximum Ratings
(Note 1)
Recommended Operating
Conditions
Note 1: Absolute maximum ratings are values beyond which the device
may be damaged or have its useful life impaired. Functional operation
under these conditions is not implied.
Note 2: Either voltage limit or current limit is sufficient to protect inputs.
DC Electrical Characteristics
Storage Temperature
-
65
C to
+
150
C
Ambient Temperature under Bias
-
55
C to
+
125
C
Junction Temperature under Bias
-
55
C to
+
150
C
V
CC
Pin Potential to Ground Pin
-
0.5V to
+
7.0V
Input Voltage (Note 2)
-
0.5V to
+
7.0V
Input Current (Note 2)
-
30 mA to
+
5.0 mA
Voltage Applied to Output
in HIGH State (with V
CC
=
0V)
Standard Output
-
0.5V to V
CC
3-STATE Output
-
0.5V to
+
5.5V
Current Applied to Output
in LOW State (Max)
twice the rated I
OL
(mA)
ESD Last Passing Voltage (Min)
4000V
Free Air Ambient Temperature
0
C to
+
70
C
Supply Voltage
+
4.5V to
+
5.5V
Symbol
Parameter
Min
Typ
Max
Units
V
CC
Conditions
V
IH
Input HIGH Voltage
2.0
V
Recognized as a HIGH Signal
V
IL
Input LOW Voltage
0.8
V
Recognized as a LOW Signal
V
CD
Input Clamp Diode Voltage
-
1.2
V
Min
I
IN
=
-
18 mA (Non I/O Pins)
V
OH
Output HIGH
10% V
CC
2.0
V
Min
I
OH
=
-
15 mA (A
n
, B
n
)
Voltage
V
OL
Output LOW
10% V
CC
0.50
V
Min
I
OL
=
1 mA (A
n
, B
n
)
Voltage
10% V
CC
0.75
I
OL
=
12 mA (A
n
, B
n
)
I
IH
Input HIGH
5.0
A
Max
V
IN
=
2.7V (Non I/O Pins)
Current
I
BVI
Input HIGH Current
7.0
A
Max
V
IN
=
7.0V (Non I/O Pins)
Breakdown Test
I
BVIT
Input HIGH Current
0.5
mA
Max
V
IN
=
5.5V (A
n
, B
n
)
Breakdown (I/O)
I
CEX
Output HIGH
50
A
Max
V
OUT
=
V
CC
Leakage Current
V
ID
Input Leakage
4.75
V
0.0
I
ID
=
1.9
A
Test
All Other Pins Grounded
I
OD
Output Leakage
3.75
A
0.0
V
IOD
=
150 mV
Circuit Current
All Other Pins Grounded
I
IL
Input LOW Current
-
0.6
mA
Max
V
IN
=
0.5V (Non I/O Pins)
I
IH
+
I
OZH
Output Leakage Current
70
A
Max
V
OUT
=
2.7V (A
n
, B
n
)
I
IL
+
I
OZL
Output Leakage Current
-
650
A
Max
V
OUT
=
0.5V (A
n
, B
n
)
I
OS
Output Short-Circuit Current
-
100
-
225
mA
Max
V
OUT
=
0V
I
ZZ
Bus Drainage Test
500
A
0.0V
V
OUT
=
5.25
I
CCL
Power Supply Current (74F2645)
82
mA
Max
V
O
=
LOW, V
IN
=
0.2V
I
CCZ
Power Supply Current (74F2645)
95
mA
Max
V
O
=
HIGH Z
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4
74F2645
AC Electrical Characteristics
Basic FAST Circuit Showing Series Resistor Placement
Symbol
Parameter
T
A
=
+
25
C
T
A
=
0
C to
+
70
C
Units
V
CC
=
+
5.0V
V
CC
=
+
5.0V
C
L
=
50 pF
C
L
=
50 pF
Min
Typ
Max
Min
Max
t
PLH
Propagation Delay
1.5
6.0
1.5
7.0
ns
t
PHL
A Input to B Output
2.5
7.5
2.5
8.0
t
PLH
Propagation Delay
1.5
6.0
1.5
7.0
ns
t
PHL
B Input to A Output
2.5
7.5
2.5
8.0
t
PZH
Enable Time
2.5
8.0
2.0
9.0
ns
t
PZL
OE Input to A Output
2.5
8.5
2.0
8.5
t
PHZ
Disable Time
1.5
7.0
1.0
8.0
t
PLZ
OE Input to A Output
1.0
5.5
1.0
5.5
t
PZH
Enable Time
2.5
7.5
2.0
9.5
ns
t
PZL
OE Input to B Output
2.5
8.5
2.5
9.0
t
PHZ
Disable Time
1.5
6.5
1.0
7.5
t
PLZ
OE Input to B Output
1.0
6.5
1.0
6.5
5
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7
4F2645 O
c
t
a
l
Bus T
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ansc
eiver
Physical Dimensions
inches (millimeters) unless otherwise noted
20-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-013, 0.300 Wide
Package Number M20B
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.
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