SN75970B Datasheet, PDF (1/23 Pages) Texas Instruments – SCSI DIFFERENTIAL CONVERTER-CONTROL

SN75970B
SCSI DIFFERENTIAL CONVERTER-CONTROL
SLLS323A – NOVEMBER 1999 – REVISED JANUARY 2000
D Provides High-Voltage Differential SCSI
from Single-Ended Controller When Used
DGG OR DL PACKAGE
(TOP VIEW)
With the SN75971B Data Transceiver
D Nine Transceivers Meet or Exceed the
Requirements of ANSI Standard EIA-485
and ISO-8482 Standards
D ESD Protection on Bus Pins to 12 kV
D Packaged in Shrink Small-Outline Package
with 25 mil Terminal Pitch and Thin
Small-Package with 20 mil Terminal Pitch
D Low Disabled Supply Current 32 mA Typ
D Thermal Shutdown Protection
D Positive- and Negative-Current Limiting
D Power-Up/-Down Glitch Protection
D Open-Circuit Failsafe Receivers
RSTFLTR ₁
RESET ₂
DSENS ₃
CLK40 4
GND 5
AATN – 6
TEST 7
AACK – 8
TIMEOUT 9
AREQ – 10
AC/D – 11
V_CC 12
GND 13
GND 14
56 ^X2
55 ^X1/CLK20
54 ^NC
53 BATN –
52 BATN+
51 BACK –
50 BACK+
49 BREQ –
48 BREQ+
47 BC/D –
46 BC/D+
45 V_CC
44 GND
43 GND
description
GND 15
GND 16
42 GND
41 GND
The SN75970B SCSI differential converter-
GND 17 40 GND
control, when used in conjunction with one or
more of its companion data transceiver(s),
V_CC 18
DRVBUS 19
39 V_CC
38 BMSG –
provides the superior electrical performance of
SDB 20 37 BMSG+
differential SCSI from a single-ended SCSI bus
AMSG – 21 36 BI/O –
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.
AI/O – 22
ASEL– ²³
NC ²⁴
ABSY – ²⁵
NC ²⁶
ARST – ²⁷
35 BI/O+
34 _BSEL+
33 _{BSEL –}
32 _BBSY+
31 _{BBSY –}
30 _BRST+
The SN75970B is available in a B2 (20 Mxfer)
NC ^{28 29} BRST –
version and a B1 (10 Mxfer) version.
In a typical differential SCSI node, the SCSI
controller provides the enables for each external
RS-485 transceiver. This could require as many
NC – No internal connection
Terminals 13 through 17 and 40 through 44 are
connected together to the package lead frame and
signal ground.
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.
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.
• POST OFFICE BOX 655303 DALLAS, TEXAS 75265
Copyright © 2000, Texas Instruments Incorporated
1