SN75971B

SCSI DIFFERENTIAL CONVERTER-DATA

SLLS322A – NOVEMBER 1999 – REVISED JANUARY 2000

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POST OFFICE BOX 655303

From Single-Ended Controller When Used

With the SN75970B Control Transceiver

Standard RS-485 and ISO-8482 Standards

with 25 mil Terminal Pitch and Thin

Small-Package with 20 mil Terminal Pitch

description

The SN75971B SCSI differential converter-data is a

9-channel RS-485 transceiver. When used in conjunc-

tion with its companion control transceiver, the

SN75970B, the resulting chip set provides the superior

electrical performance of differential SCSI from a

single-ended

SCSI

bus

or

controller.

A

16-bit

Ultra-SCSI (or Fast-20) SCSI bus can be implemented

with just three devices (two data and one control) in the

space efficient, 56-pin, shrink small-outline package

(SSOP) or thin shink small outline package (TSSOP)

and a few external components. An 8-bit SCSI bus

requires only one data and one control transceiver.

The SN75971B is available in a B2 (20 Mxfer)

version and a B1 (10 Mxfer) version.

In a typical differential SCSI node, the SCSI controller

provides an enable for each external RS-485

transceiver channel. This could require as many as 27

extra 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 SCSIcontrol signals, the SN75970B control transceiver decodes the

state of the bus and enables the SN75971B data transceiver to transmit the single-ended SCSI input signals

(A side) differentially to the cable or receive the differential cable signals (B side) and drive the single-ended

outputs to the controller.

A reset function, which disables all outputs and clears internal latches, can be accomplished from two external

inputs and two internally-generated signals. RESET (reset) and DSENS (differential sense) are available to

external circuits for a bus reset or to disable all outputs should a single-ended cable be inadvertently connected

to a differential connector. Internally-generated power-up and thermal-shutdown signals have the same affect

when the supply voltage is below approximately 3.5 V or the junction temperature exceeds 175

°C.

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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SDB

DRVBUS

GND

ADBP –

NC

ADB7 –

NC

ADB6 –

NC

ADB5 –

NC

GND

GND

GND

GND

GND

ABD4 –

NC

ADB3 –

NC

ADB2 –

NC

ADB1 –

NC

ADB0 –

NC

DSENS

RESET

GND

BDBP –

BDBP +

BDB7 –

BDB7 +

BDB6 –

BDB6 +

BDB5 –

BDB5 +

GND

GND

GND

GND

GND

BDB4 –

BDB4 +

BDB3 –

BDB3 +

BDB2 –

BDB2 +

BDB1 –

BDB1 +

BDB0 –

BDB0 +

DGG OR DL PACKAGE

(TOP VIEW)

NC – No internal connection

Pins 13 – 17 and 40 – 44 are connected

together to the package lead frame and

to signal ground.