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SN74ALS638A, SN74ALS639A, SN74AS638A, SN74AS639
OCTAL BUS TRANSCEIVERS
SDAS123A – DECEMBER 1983 – REVISED JANUARY 1995
•
•
•
•
Bidirectional Bus Transceivers in
High-Density 20-Pin Packages
Choice of True or Inverting Logic
A-Bus Outputs Are Open Collector;
B-Bus Outputs Are 3 State
Package Options Include Plastic
Small-Outline (DW) Packages and
Standard Plastic (N) 300-mil DIPs
DEVICE
A
OUTPUT
Open collector
Open collector
B
OUTPUT
3 state
3 state
LOGIC
Inverting
True
DW OR N PACKAGE
(TOP VIEW)
SN74ALS638A, SN74AS638A
SN74ALS639A, SN74AS639
DIR
A1
A2
A3
A4
A5
A6
A7
A8
GND
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
V
CC
OE
B1
B2
B3
B4
B5
B6
B7
B8
description
These octal bus transceivers are designed for asynchronous two-way communication between open-collector
and 3-state buses. The devices transmit data from the A bus (open-collector) to the B bus (3 state) or from the
B bus to the A bus, depending on the logic level at the direction-control (DIR) input. The output-enable (OE) input
can be used to disable the device so the buses are isolated.
The -1 version of SN74ALS638A is identical to the standard version, except that the recommended maximum
I
OL
is increased to 48 mA.
The SN74ALS638A, SN74ALS639A, SN74AS638A, and SN74AS639 are characterized for operation from 0°C
to 70°C.
FUNCTION TABLE
INPUTS
OE
L
L
H
DIR
L
H
X
OPERATION
SN74ALS638A
SN74AS638A
B data to A bus
A data to B bus
Isolation
SN74ALS639A
SN74AS639
B data to A bus
A data to B bus
Isolation
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
Copyright
©
1995, Texas Instruments Incorporated
POST OFFICE BOX 655303
•
DALLAS, TEXAS 75265
1
SN74ALS638A, SN74ALS639A, SN74AS638A, SN74AS639
OCTAL BUS TRANSCEIVERS
SDAS123A – DECEMBER 1983 – REVISED JANUARY 1995
logic symbols
†
SN74ALS638A, SN74AS638A
OE
DIR
19
1
G3
3 EN1 [BA]
3 EN2 [AB]
1
2
A2
A3
A4
A5
A6
A7
A8
3
4
5
6
7
8
9
17
16
15
14
13
12
11
B2
B3
B4
B5
B6
B7
B8
A2
A3
A4
A5
A6
A7
A8
3
4
5
6
7
8
9
18
B1
OE
DIR
19
1
SN74ALS639A, SN74AS639
G3
3 EN1 [BA]
3 EN2 [AB]
1
2
17
16
15
14
13
12
11
B2
B3
B4
B5
B6
B7
B8
18
B1
A1
2
A1
2
† These symbols are in accordance with ANSI/IEEE Std 91-1984 and IEC Publication 617-12.
logic diagrams (positive logic)
SN74ALS638A, SN74AS638A
OE
19
OE
19
SN74ALS639A, SN74AS639
DIR
1
DIR
1
A1
2
18
B1
A1
2
18
B1
To Seven Other Transceivers
To Seven Other Transceivers
absolute maximum ratings over operating free-air temperature range (unless otherwise noted)
‡
Supply voltage, V
CC
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 V
Input voltage, V
I
: All inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 V
A-bus I/O ports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 V
B-bus I/O ports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5 V
Operating free-air temperature range, T
A
: SN74ALS638A, SN74ALS639A . . . . . . . . . . . . . . . . . 0°C to 70°C
Storage temperature range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 65°C to 150°C
‡ Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, and
functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not
implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
2
POST OFFICE BOX 655303
•
DALLAS, TEXAS 75265
SN74ALS638A, SN74ALS639A, SN74AS638A, SN74AS639
OCTAL BUS TRANSCEIVERS
SDAS123A – DECEMBER 1983 – REVISED JANUARY 1995
recommended operating conditions
SN74ALS638A
SN74ALS639A
MIN
VCC
VIH
VIL
VOH
IOH
IOL
Supply voltage
High-level input voltage
Low-level input voltage
High-level output voltage
High-level output current
Low-level
Low level output current
A ports
B ports
A or B ports
0
4.5
2
0.8
5.5
– 15
24
48†
70
NOM
5
MAX
5.5
V
V
V
V
mA
mA
°C
UNIT
TA
Operating free-air temperature
† Applies only to the SN74ALS638A-1 version and only if VCC is between 4.75 V and 5.25 V
electrical characteristics over recommended operating free-air temperature range (unless
otherwise noted)
PARAMETER
VIK
IOH
VOH
TEST CONDITIONS
VCC = 4.5 V,
VCC = 4.5 V,
VCC = 4.5 V to 5.5 V,
B ports
VCC = 4 5 V
4.5
II = – 18 mA
VOH = 5.5 V
IOH = – 0.4 mA
IOH = – 3 mA
IOH = – 15 mA
IOL = 12 mA
IOL = 24 mA
IOL = 48 mA†
VI = 7 V
VI = 5.5 V
VI = 2 7 V
2.7
VI = 0 4 V
0.4
VO = 2.25 V
Outputs high
Outputs low
Outputs disabled
Outputs high
SN74ALS639A
VCC = 5.5 V
Outputs low
Outputs disabled
– 30
18
26
16
25
30
33
VCC – 2
2.4
2
0.25
0.35
0.35
0.4
0.5
0.5
0.1
0.1
20
20
– 0.1
– 0.1
– 112
30
41
30
40
50
54
mA
mA
µA
mA
mA
V
3.2
SN74ALS638A
SN74ALS639A
MIN
A ports
TYP‡
MAX
– 1.5
0.1
V
mA
V
UNIT
VOL
A or B ports
Control inputs
A or B ports
Control inputs
A or B ports§
Control inputs
A or B ports§
B ports
SN74ALS638A
VCC = 4.5 V
II
IIH
IIL
IO¶
VCC = 5 5 V
5.5
VCC = 5 5 V
5.5 V,
VCC = 5 5 V
5.5 V,
VCC = 5.5 V,
VCC = 5.5 V
ICC
† Applies only to the SN74ALS638A-1 version and only if VCC is between 4.75 V and 5.25 V
‡ All typical values are at VCC = 5 V, TA = 25°C.
§ For I/O ports, the parameters IIH and IIL include the off-state output current.
¶ The output conditions have been chosen to produce a current that closely approximates one half of the true short-circuit output current, IOS.
POST OFFICE BOX 655303
•
DALLAS, TEXAS 75265
3
SN74ALS638A, SN74ALS639A, SN74AS638A, SN74AS639
OCTAL BUS TRANSCEIVERS
SDAS123A – DECEMBER 1983 – REVISED JANUARY 1995
switching characteristics (see Figure 1)
VCC = 4.5 V to 5.5 V,
CL = 50 pF,
RL = 680
Ω
(A outputs)
,
R1 = R2 = 500
Ω
(B outputs)
,
TA = MIN to MAX†
SN74ALS638A
MIN
tPLH
tPHL
tPLH
tPHL
tPLH
tPHL
tPZH
tPZL
tPHZ
tPLZ
A
B
2
B
A
A
B
B
2
8
8
5
OE
OE
OE
10
5
5
2
3
MAX
12
12
25
30
25
45
20
22
10
15
SN74ALS639A
MIN
2
2
10
5
10
10
6
8
2
3
MAX
12
12
30
22
30
35
21
25
10
16
ns
ns
ns
ns
ns
PARAMETER
FROM
(INPUT)
TO
(OUTPUT)
UNIT
† For conditions shown as MIN or MAX, use the appropriate value specified under recommended operating conditions.
absolute maximum ratings over operating free-air temperature range (unless otherwise noted)
‡
Supply voltage, V
CC
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 V
Input voltage, V
I
: All inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 V
A-bus I/O ports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 V
B-bus I/O ports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5 V
Operating free-air temperature range, T
A
: SN74AS638A, SN74AS639 . . . . . . . . . . . . . . . . . . . . 0°C to 70°C
Storage temperature range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 65°C to 150°C
‡ Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, and
functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not
implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
recommended operating conditions
SN74AS638A
SN74AS639
MIN
VCC
VIH
VIL
VOH
IOH
IOL
TA
Supply voltage
High-level input voltage
Low-level input voltage
High-level output voltage
High-level output current
Low-level output current
Operating free-air temperature
A ports
B ports
A or B ports
0
4.5
2
0.8
5.5
– 15
64
70
NOM
5
MAX
5.5
V
V
V
V
mA
mA
°C
UNIT
4
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•
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