CONNECTION DIAGRAMS DIP (TOP VIEW)
18 17 16 15 14 13
1 2 3 4 5 6 7
20 19
8
VCC
DIR
B1 B2 B3 B5B4 B6
A1 A2 A3 A4 A5 A6 A7 9 10
A8 GND
12 11
B7 B8
18 17 16 15 14 13
1 2 3 4 5 6 7
20 19
8
VCC
DIR
B1 B2 B3 B5B4 B6
A1 A2 A3 A4 A5 A6 A7 9 10
A8 GND
12 11
B7 B8
SN54/74LS640
SN54/74LS642 SN54/74LS641
SN54/74LS645
ENABLE
GENABLE
G
5-1
FAST AND LS TTL DATA
OCTAL BUS TRANSCEIVERS
These octal bus transceivers are designed for asynchronous two-way
communication between data buses. Control function implementation
minimizes external timing requirements. These circuits allow data transmis-
sion from the A bus to B or from the B bus to A bus depending upon the logic
level of the direction control (DIR) input. Enable input (G) can disable the
device so that the buses are effectively isolated.
DEVICE OUTPUT LOGIC
LS640 3-State Inverting
LS641 Open-Collector True
LS642 Open-Collector Inverting
LS645 3-State True
FUNCTION TABLE
CONTROL
INPUTS
OPERATION
INPUTS
LS640
LS642
LS641
LS645
G DIR
LS640
LS642
LS641
LS645
L L B data to A bus B data to A bus
L H A data to B bus A data to B bus
H X Isolation Isolation
H = HIGH Level, L = LOW Level, X = Irrelevant
SN54/74LS640
SN54/74LS641
SN54/74LS642
SN54/74LS645
OCTAL BUS TRANSCEIVERS
LOW POWER SCHOTTKY
ORDERING INFORMATION
SN54LSXXXJ Ceramic
SN74LSXXXN Plastic
SN74LSXXXDW SOIC
20
1
J SUFFIX
CERAMIC
CASE 732-03
20 1
N SUFFIX
PLASTIC
CASE 738-03
20
1
DW SUFFIX
SOIC
CASE 751D-03
5-2
FAST AND LS TTL DATA
SN54/74LS640 • SN54/74LS645
GUARANTEED OPERATING RANGES
Symbol Parameter Min Typ Max Unit
VCC Supply Voltage 54
74 4.5
4.75 5.0
5.0 5.5
5.25 V
TAOperating Ambient Temperature Range 54
74 –55
025
25 125
70 °C
IOH Output Current — High
54, 74 –3.0 mA
OH
54
74 –12
–15 mA
IOL Output Current — Low 54
74 12
24 mA
DC CHARACTERISTICS OVER OPERATING TEMPERATURE RANGE (unless otherwise specified)
Symbol
Parameter
Limits
Unit
Test Conditions
Symbol
Parameter
Min Typ Max
Unit
Test Conditions
VIH Input HIGH Voltage 2.0 V Guaranteed Input HIGH Voltage for
All Inputs
VIL
Input LOW Voltage
54 0.5
V
Guaranteed Input LOW Voltage for
VIL
Input LOW Voltage
74 0.6
V
Guaranteed Input LOW Voltage for
All Inputs
VIK Input Clamp Diode Voltage –0.65 –1.5 V VCC = MIN, IIN = –18 mA
VOH
Output HIGH Voltage
54, 74 2.4 3.4 V VCC = MIN, IOH = 3.0 mA
VOH
Output HIGH Voltage
54, 74 2.0 V VCC = MIN, IOH = MAX
VOL
Output LOW Voltage
54, 74 0.25 0.4 V IOL = 12 mA
VCC = VCC MIN,
VIN = VIL or VIH
per Truth Table
VOL
Output LOW Voltage
74 0.35 0.5 V IOL = 24 mA
VIN = VIL or VIH
per Truth Table
IOZH Output Off Current HIGH 20 µA VCC = MAX, VOUT = 2.7 V
IOZL Output Off Current LOW –400 µA VCC = MAX, VOUT = 0.4 V
IIH
A or B, DIR or G 20 µA VCC = MAX, VIN = 2.7 V
IIH Input HIGH Current
DIR or G 0.1 mA VCC = MAX, VIN = 7.0 V
IH
A or B 0.1 mA VCC = MAX, VIN = 5.5 V
IIL Input LOW Current –0.4 mA VCC = MAX, VIN = 0.4 V
IOS Output Short Circuit Current (Note 1) –40 –225 mA VCC = MAX
ICC
Power Supply Current
Total Output HIGH 70
mA
VCC = MAX
ICC
Total, Output LOW 90
mA
VCC = MAX
Total at HIGH Z 95
Note 1: Not more than one output should be shorted at a time, nor for more than 1 second.
AC CHARACTERISTICS (TA = 25°C, VCC = 5.0 V)
Symbol
Parameter
Limits
Unit
Test Conditions
Symbol
Parameter
LS640 LS645
Unit
Test Conditions
Symbol
Parameter
Min Typ Max Min Typ Max
Unit
Test Conditions
tPLH
tPHL Propagation Delay
A to B 6.0
8.0 10
15 8.0
11 15
15 ns
CL = 45 pF,
RL = 667 Ω
tPLH
tPHL Propagation Delay
B to A 6.0
8.0 10
15 8.0
11 15
15 ns
C
L = 45 pF,
RL = 667 Ω
tPZL
tPZH Output Enable Time
G, DIR to A 31
23 40
40 31
26 40
40 ns
CL = 45 pF,
RL = 667 Ω
tPZL
tPZH Output Enable Time
G, DIR to B 31
23 40
40 31
26 40
40 ns
tPLZ
tPHZ Output Disable Time
G, DIR to A 15
15 25
25 15
15 25
25 ns
CL = 5.0 pF
tPLZ
tPHZ Output Disable Time
G, DIR to B 15
15 25
25 15
15 25
25 ns
CL = 5.0 pF
5-3
FAST AND LS TTL DATA
SN54/74LS641 • SN54/74LS642
GUARANTEED OPERATING RANGES
Symbol Parameter Min Typ Max Unit
VCC Supply Voltage 54
74 4.5
4.75 5.0
5.0 5.5
5.25 V
TAOperating Ambient Temperature Range 54
74 –55
025
25 125
70 °C
VOH Output Current — High 54, 74 5.5 V
IOL Output Current — Low 54
74 12
24 mA
DC CHARACTERISTICS OVER OPERATING TEMPERATURE RANGE (unless otherwise specified)
Symbol
Parameter
Limits
Unit
Test Conditions
Symbol
Parameter
Min Typ Max
Unit
Test Conditions
VIH Input HIGH Voltage 2.0 V Guaranteed Input HIGH Voltage for
All Inputs
VIL
Input LOW Voltage
54 0.5
V
Guaranteed Input LOW Voltage for
All Inputs
VIL
Input LOW Voltage
74 0.6
V
Guaranteed Input LOW Voltage for
All Inputs
VIK Input Clamp Diode Voltage –0.65 –1.5 V VCC = MIN, IIN = –18 mA
IOH Output HIGH Current 54, 74 100 µA VCC = MIN, VOH = MAX
VOL
Output LOW Voltage
54, 74 0.25 0.4 V IOL = 12 mA
VCC = VCC MIN,
VIN = VIL or VIH
per Truth Table
VOL
Output LOW Voltage
74 0.35 0.5 V IOL = 24 mA
VIN = VIL or VIH
per Truth Table
IIH
Input HIGH Current
20 µA VCC = MAX, VIN = 2.7 V
IIH
Input HIGH Current
–0.1 mA VCC = MAX, VIN = 7.0 V
IIL Input LOW Current –0.4 mA VCC = MAX, VIN = 0.4 V
ICC
Power Supply Current
Total, Output HIGH 70
mA
VCC = MAX
ICC
Total, Output LOW 90
mA
VCC = MAX
Total at HIGH Z 95
AC CHARACTERISTICS (TA = 25°C, VCC = 5.0 V)
Symbol
Parameter
Limits
Unit
Test Conditions
Symbol
Parameter
LS641 LS642
Unit
Test Conditions
Symbol
Parameter
Min Typ Max Min Typ Max
Unit
Test Conditions
tPLH
tPHL Propagation Delay,
A to B 17
16 25
25 19
14 25
25 ns
CL = 45 pF,
RL = 667 Ω
tPLH
tPHL Propagation Delay,
B to A 17
16 25
25 19
14 25
25 ns
C
L = 45 pF,
RL = 667 Ω
tPLH
tPHL Propagation Delay,
G, DIR to A 23
34 40
50 26
43 40
60 ns
CL = 45 pF,
RL = 667 Ω
tPLH
tPHL Propagation Delay,
G, DIR to B 25
37 40
50 28
39 40
60 ns