LX5218CDW Просмотр технического описания (PDF) - Microsemi Corporation
Номер в каталоге
Компоненты Описание
Список матч
LX5218CDW Datasheet PDF : 12 Pages
| |||
LX5218
TERM POWER
PRODUCT DATABOOK 1996/1997
9-CHANNEL PLUG AND PLAY SCSI TERMINATOR
PRODUCTION DATA SHEET
BLOCK DIAGRAM
THERMAL
LIMITING
CIRCUIT
CURRENT
BIASING
CIRCUIT
24mA CURRENT
LIMITING CIRCUIT
DISC1
DISC2
2.85V
UltraMAX
DATA OUTPUT
PIN DB(0)
1 OF 9 CHANNELS
FUNCTIONAL DESCRIPTION
Cable transmission theory suggests to optimize signal speed respond to line demands by delivering 24mA on assertion and
and quality, the termination should act both as an ideal voltage by imposing 2.85V on deassertion. In order to disable the
reference when the line is released (deasserted) and as an device, the DISC1 and DISC2 pins must be driven logic Low.
ideal current source when the line is active (asserted). This mode of operation places the device in a sleep state where
Common active terminators,
a meager 275µA of quiescent cur-
which consist of Linear Regulators
in series with resistors (typically
110Ω), are a compromise. As the
line voltage increases, the amount
POWER UP / POWER DOWN FUNCTION TABLE
DISC1 DISC2
Outputs
Quiescent
Current
rent is consumed. Additionally, all
outputs are in a Hi-Z (impedance)
state. Sleep mode can be used for
power conservation or to com-
of current decreases linearly by the
equation V = I * R. The LX5218,
H
with its unique new architecture
H
applies the maximum amount of
L
H
Enabled
L
Enabled
H
Enabled
6mA
6mA
6mA
pletely eliminate the terminator
from the SCSI chain. In the second
case, termination node capacitance
is important to consider. The ter-
current regardless of line voltage
L
L
Disabled
275µA
minator will appear as a parasitic
until the termination high thresh- Open Open
Enabled
6mA
distributed capacitance on the line,
old (2.85V) is reached.
which can detract from bus per-
Acting as a near ideal line ter-
formance. For this reason, the
minator, the LX5218 closely reproduces the optimum case LX5218 has been optimized to have only 3pF of capacitance
when the device is enabled. To enable the device the DISC1 per output in the sleep state.
and DISC2 Pins must be pulled logic High, Open, or any
An additional feature of the LX5218 is its compatibility with
combination of both High and Low. During this mode of active negation drivers. The device handles up to 60mA of
operation, quiescent current is 6mA and the device will sink current for drivers which exceed the 2.85V output high.
4
Copyright © 1997
Rev. 1.7 12/97
Share Link: 