ML6518 Datasheet, PDF (1/8 Pages) Micro Linear Corporation – 18 Line Hot-Insertable Active SCSI Terminator

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
s Fully monolithic IC solution providing active
termination for 18 lines of the SCSI bus
s Provides onboard support for hot-insertability on the
SCSI bus
s Low dropout voltage (1V) linear regulator, trimmed for
accurate termination current
s Low disconnect capacitance (typically < 5pF)
s Logic pin with active pull-up to disconnect terminator
from the SCSI bus
s Current sinking capability in excess of 8.3mA 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 400mA and sink 150mA while
maintaining regulation
s Current limit and thermal shutdown protection
*This Part Is End Of Life As Of August 1, 2000
BLOCK DIAGRAM
TERMPWR
VREF
DISCNKT
GND
LINEAR
REGULATOR
1V DROPOUT
2.85V
NCLAMP
MOSFETs WITH I_MAX = 24mA
...
NCLAMP = Negative Clamp
NCLAMP
NCLAMP
...
L1
L2
L18
18 TERMINATION LINES
2.85V
RTRIM
VREF _CONTROL
BLOCK
...
Circuit design patent pending.
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