August 2000
ML6518*
18 Line Hot-Insertable Active SCSI Terminator
GENERAL DESCRIPTION
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.
FEATURES
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Fully monolithic IC solution providing active
termination for 18 lines of the SCSI bus
Provides onboard support for hot-insertability on the
SCSI bus
Low dropout voltage (1V) linear regulator, trimmed for
accurate termination current
Low disconnect capacitance (typically < 5pF)
Logic pin with active pull-up to disconnect terminator
from the SCSI bus
Current sinking capability in excess of 8.3mA per line to
handle active negation driver overshoots above 2.85V
Negative clamping on all lines to handle signal
assertion transients
Regulator can source 400mA and sink 150mA while
maintaining regulation
Current limit and thermal shutdown protection
*This Part Is End Of Life As Of August 1, 2000
BLOCK DIAGRAM
TERMPWR
V
REF
DISCNKT
2.85V
LINEAR
REGULATOR
1V DROPOUT
2.85V
GND
R
TRIM
V
REF
CONTROL
BLOCK
MOSFETs WITH I
MAX
= 24mA
...
NCLAMP
...
...
...
NCLAMP
NCLAMP
L1
L2
...
L18
18 TERMINATION LINES
NCLAMP = Negative Clamp
Circuit design patent pending.
1
MICRO-LINEAR [ MICRO LINEAR CORPORATION ]
