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DS2127

Ultra3 LVD/SE SCSI 14-Line Terminator

Maxim Integrated 

Ultra3 LVD/SE SCSI 14-Line Terminator

Figure 1. Block Diagram

DIFF_CAP

ISO

2.15V

0.6V

DELAY/

LVD

LVD

FILTER

SE

HVD

SE

THERMAL

SHUTDOWN

10µA

LVD SE HVD

1.30V

DS2127

CONTROL LOGIC

BANDGAP

2.15V

REFGEN AND 1.30V

TRIM

0.6V

1.25V 2.85V

(LVD) (SE)

SE

HVD/ISO

LVD

ALL SWITCHES UP

ALL SWITCHES CENTER

ALL SWITCHES DOWN

110Ω

52Ω

124Ω

52Ω

110Ω

52Ω

124Ω

52Ω

VREF

LVD

SE

DIFFSENS

R1N

R1P

R14N

R14P

Pin Description

PIN

1, 2, 11–24,

37–48

NAME

FUNCTION

Signal Termination. Connect to SCSI bus signal lines. Asserting ISO removes the terminators from the

R_ _ P, R_ _ N SCSI bus. R_ _ P pins are the ground line for SE operation and the positive lines in differential mode.

R_ _ N pins are the signal lines in SE operation and the negative lines in differential mode.

3

4–9, 28–33

TPWR

HS_GND

Termination Power. Connect to the SCSI TERMPWR line and decouple with a ceramic

2.2µF capacitor.

Heat-Sink Ground. Internally connected to the mounting pad. These pins must be connected to

ground. These pins should be connected to a ground plane with the layout optimized for

heat transfer.

Regulator Output Voltage. This must be decoupled with a 4.7µF capacitor. Asserting ISO floats this

10

VREF

output. A high-frequency capacitor (0.1µF) should also be placed on the VREF pin in applications that

use fast rise/fall-time drivers.

25

GND

Signal Ground

26

SE

SE Mode Indicator. A high state indicates SE mode detected on SCSI bus.

27

LVD

LVD Mode Indicator. A high state indicates LVD mode detected on SCSI.

34

DIFF_CAP

DIFFSENSE Capacitor. Connect a 0.1µF capacitor for the DIFFSENSE filter. Input to detect the type of

device (differential or single-ended) on the SCSI bus.

35

DIFFSENS DIFFSENSE. Output to drive the SCSI bus DIFFSENS line.

Isolation Input. When pulled high, terminating resistors and biasing current sources are removed from

36

ISO

the SCSI bus. When not connected to ground, the pin has a 10µA current source pulling the pin to the

high state.

4 _____________________________________________________________________

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