SN75970B

SCSI DIFFERENTIAL CONVERTER-CONTROL

SLLS323A – NOVEMBER 1999 – REVISED JANUARY 2000

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POST OFFICE BOX 655303

from Single-Ended Controller When Used

With the SN75971B Data Transceiver

Requirements of ANSI Standard EIA-485

and ISO-8482 Standards

with 25 mil Terminal Pitch and Thin

Small-Package with 20 mil Terminal Pitch

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.

The SN75970B is available in a B2 (20 Mxfer)

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

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.

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RSTFLTR

RESET

DSENS

CLK40

GND

AATN –

TEST

AACK –

TIMEOUT

AREQ –

AC/D –

GND

GND

GND

GND

GND

DRVBUS

SDB

AMSG –

AI/O –

ASEL–

NC

ABSY –

NC

ARST –

NC

X2

X1/CLK20

NC

BATN –

BATN+

BACK –

BACK+

BREQ –

BREQ+

BC/D –

BC/D+

GND

GND

GND

GND

GND

BMSG –

BMSG+

BI/O –

BI/O+

BSEL+

BSEL –

BBSY+

BBSY –

BRST+

BRST –

DGG OR DL PACKAGE

(TOP VIEW)

NC – No internal connection

Terminals 13 through 17 and 40 through 44 are

connected together to the package lead frame and

signal ground.