August 2000

ML6518

*

18 Line Hot-Insertable Active SCSI Terminator

GENERAL DESCRIPTION

NCLAMP = Negative Clamp

Circuit design patent pending.

1

FEATURES

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Fully monolithic IC solution providing active

termination for 18 lines of the SCSI bus

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Provides onboard support for hot-insertability on the

SCSI bus

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Low dropout voltage (1V) linear regulator, trimmed for

accurate termination current

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Low disconnect capacitance (typically < 5pF)

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Logic pin with active pull-up to disconnect terminator

from the SCSI bus

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Current sinking capability in excess of 8.3mA per line to

handle active negation driver overshoots above 2.85V

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Negative clamping on all lines to handle signal

assertion transients

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Regulator can source 400mA and sink 150mA while

maintaining regulation

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Current limit and thermal shutdown protection

The ML6518 BiCMOS 18 line SCSI terminator provides

active termination in SCSI systems using single-ended

drivers and receivers. Active SCSI termination helps to

effectively control analog transmission line effects such as

ringing, noise, crosstalk, and ground bounce. In addition,

the ML6518 provides support for hot insertability on the

SCSI bus.

The ML6518 provides a V-I characteristic optimized to

minimize transmission line effects during both signal

negation and assertion using a MOSFET-based

architecture. The desired V-I characteristic is achieved by

trimming one resistor in the control block. Internal

clamping controls signal assertion transients and provides

current sink capability to handle active negation driver

overshoots above 2.85V. It provides a 2.85V reference

through an internal low dropout (1V) linear regulator.

The ML6518 also provides a disconnect function which

effectively removes the terminator from the SCSI bus. The

disconnect mode capacitance is typically less than 5pF

per line. Current limiting and thermal shutdown protection

are also included.

*This Part Is End Of Life As Of August 1, 2000

BLOCK DIAGRAM

TERMPWR

LINEAR

REGULATOR

1V DROPOUT

2.85V

DISCNKT

CONTROL

BLOCK

NCLAMP

18 TERMINATION LINES

. . .

. . .

NCLAMP

NCLAMP

. . .

GND

L2

L18

L1

2.85V