February 1997

ML6599

*

Hot-Insertable Active SCSI Terminator

GENERAL DESCRIPTION

The ML6599 BiCMOS 9 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 ML6599 provides support for hot-insertability on the

SCSI bus.

The ML6599 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 ML6599 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.

*Some Packages Are Obsolete

BLOCK DIAGRAM

NCLAMP = Negative Clamp

TERMPWR

LINEAR

REGULATOR

1V DROPOUT

2.85V

DISCNKT

CONTROL

BLOCK

NCLAMP

9 TERMINATION LINES

. . .

. . .

NCLAMP

NCLAMP

. . .

GND

L2

L9

L1

2.85V

1

FEATURES

s

Fully monolithic IC solution providing active

termination for 9 lines of the SCSI bus

s

Provides on board support for hot-insertability on the

SCSI bus

s

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

accurate termination current

s

Output capacitance typically < 5pF

s

Disconnect mode — logic pin to disconnect terminator

from the SCSI bus, <100

µA

s

Current sinking — can sink current in excess of 10mA

per line to handle active negation driver overshoots

above 2.85V

s

Negative clamping on all lines to handle signal

assertion transients

s

Regulator can source 200mA and sink 100mA while

maintaining regulation

s

Current limit & thermal shutdown protection