LVD SCSI 27-Line Regulator

4

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Detailed Description

The DS2129 provides three regulated outputs. The

REG1 provides a 1.75V output, and the REG2 provides

a 0.75V output. Both regulators can sink and source

200mA of current. These regulators are current-limited

to less than 700mA. The thermal-shutdown circuit dis-

ables the output buffers should the die temperature

exceed +150°C. With a pi network of resistors (475

Ω,

121

Ω, 475Ω) connected to these two outputs, the

DS2129 provides common-mode bias, differential bias,

and common impedance and differential impedance,

as required in a terminator specified in SPI-2 and SPI-3

standards for a SCSI system. The third regulator pro-

vides a 1.3V output for DIFFSENSE signaling.

Chip Information

TRANSISTOR COUNT: 3778 CMOS and 80 BIPOLAR

PROCESS: BiCMOS

SUBSTRATE CONNECTED TO GROUND

Thermal Information

Thermal Resistance (junction-to-ambient):

Thermal Resistance (junction-to-case):

Pin Description

PIN

NAME

FUNCTION

1, 8, 9,

10, 15,

16

N.C.

No Connection. Do not connect pins.

2

TERMPWR

Termination Power. Connect to SCSI

TERMPWR line and decouple with a

4.7µF ceramic capacitor.

3

REG2

Regulator 2, 0.75V Output. Decouple

with a 4.7µF ceramic capacitor.

4

GND

Signal Ground

5, 11–14

HS_GND

Heat-Sink Ground. Internally

connected to the mounting pad.

Should be connected to ground.

6

REG1

Regulator 1, 1.75V Output. Decouple

with a 4.7µF ceramic capacitor.

7

DIFFSENSE

DIFFSENSE Output. Drives the SCSI

bus DIFFSENSE line.