SN75970B
SCSI DIFFERENTIAL CONVERTER-CONTROL
SLLS323A – NOVEMBER 1999 – REVISED JANUARY 2000
DGG OR DL PACKAGE
(TOP VIEW)
Provides High-Voltage Differential SCSI
from Single-Ended Controller When Used
With the SN75971B Data Transceiver
RSTFLTR
RESET
DSENS
CLK40
GND
X2
1
56
55
54
53
52
51
50
49
48
47
46
45
Nine Transceivers Meet or Exceed the
Requirements of ANSI Standard EIA-485
and ISO-8482 Standards
X1/CLK20
NC
2
3
BATN–
BATN+
BACK–
BACK+
BREQ–
BREQ+
BC/D–
BC/D+
4
ESD Protection on Bus Pins to 12 kV
5
Packaged in Shrink Small-Outline Package
with 25 mil Terminal Pitch and Thin
Small-Package with 20 mil Terminal Pitch
AATN–
TEST
6
7
AACK–
TIMEOUT
AREQ–
AC/D–
8
Low Disabled Supply Current 32 mA Typ
Thermal Shutdown Protection
9
10
11
12
Positive- and Negative-Current Limiting
Power-Up/-Down Glitch Protection
Open-Circuit Failsafe Receivers
V
V
CC
CC
GND 13
GND 14
44 GND
43 GND
15
16
17
18
19
20
21
22
23
24
25
26
27
28
42
41
40
39
38
37
36
35
34
33
32
31
30
29
GND
GND
GND
GND
GND
GND
description
The SN75970B SCSI differential converter-
control, when used in conjunction with one or
more of its companion data transceiver(s),
provides the superior electrical performance of
differential SCSI from a single-ended SCSI bus
controller. A 16-bit, Fast-SCSI bus can be
implemented with just three devices (two for data
and one for control) in the space-efficient, 56-pin,
shrink small-outline package (SSOP) as well as
the even smaller TSSOP and a few external
components.
V
V
CC
CC
DRVBUS
SDB
BMSG–
BMSG+
BI/O–
AMSG–
AI/O–
ASEL–
NC
BI/O+
BSEL+
BSEL–
BBSY+
BBSY–
BRST+
BRST–
ABSY–
NC
ARST–
NC
The SN75970B is available in a B2 (20 Mxfer)
version and a B1 (10 Mxfer) version.
NC – No internal connection
Terminals 13 through 17 and 40 through 44 are
connected together to the package lead frame and
signal ground.
In a typical differential SCSI node, the SCSI
controller provides the enables for each external
RS-485 transceiver. This could require as many
as 27 additional terminals for a 16-bit differential bus controller or relegate a 16-bit single-ended controller to
only an 8-bit differential bus. Using the standard nine SCSI control signals, the SN75970B control transceiver
decodes the state of the bus and enables the SN75971B data transceiver(s) to transmit the single-ended SCSI
input signals differentially to the cable or receive the differential cable signals and drive the single-ended outputs
to the controller.
The single-ended SCSI bus interface consists of CMOS bidirectional inputs and outputs. The drivers are rated
at ±16 mA of output current. The receiver inputs are pulled high with approximately 4 mA to eliminate the need
for external pullup resistors for the open-drain outputs of most single-ended SCSI controllers. The single-ended
side of the device is not intended to drive the SCSI bus directly.
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
Copyright 2000, Texas Instruments Incorporated
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.
1
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265