
SN54ALS640B, SN54AS640, SN74ALS640B, SN74AS640
OCTAL BUS TRANSCEIVERS
WITH 3-STATE OUTPUTS
SDAS122A – DECEMBER 1983 – REVISED JANUARY 1995
Copyright 1995, Texas Instruments Incorporated
1
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
• Bidirectional Bus Transceivers in
High-Density 20-Pin Packages
• Inverting Logic
• Package Options Include Plastic
Small-Outline (DW) Packages, Ceramic
Chip Carriers (FK), and Standard Plastic (N)
and Ceramic (J) 300-mil DIPs
description
These octal bus transceivers are designed for
asynchronous two-way communication between
data buses. These devices transmit data from the
A bus to the B bus or from the B bus to the A bus,
depending upon the level at the direction-control
(DIR) input. The output-enable (OE
) input can be
used to disable the device so that the buses are
effectively isolated.
The -1 version of the SN74ALS640B is identical to
the standard version, except that the
recommended maximum I
OL
for the -1 version is
increased to 48 mA. There is no -1 version of the
SN54ALS640B.
The SN54ALS640B and SN54AS640 are
characterized for operation over the full military
temperature range of –55°C to 125°C. The
SN74ALS640B and SN74AS640 are
characterized for operation from 0°C to 70°C.
FUNCTION TABLE
INPUTS
OE DIR
L L B data to A bus
L HA data to B bus
H X Isolation
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
DIR
A1
A2
A3
A4
A5
A6
A7
A8
GND
V
CC
OE
B1
B2
B3
B4
B5
B6
B7
B8
SN54ALS640B, SN54AS640 ...J PACKAGE
SN74ALS640B, SN74AS640 . . . DW OR N PACKAGE
(TOP VIEW)
3212019
9
10 11 12 13
4
5
6
7
8
18
17
16
15
14
B1
B2
B3
B4
B5
A3
A4
A5
A6
A7
SN54ALS640B, SN54AS640 . . . FK PACKAGE
(TOP VIEW)
A2
A1
DIR
B7
B6
OE
A8
GND
B8
V
CC
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.