LX5122CDBT Ver la hoja de datos (PDF) - Microsemi Corporation
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LX5122CDBT Datasheet PDF : 4 Pages
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UltraMAX
VCC VCC
DISC1
DISC2
PRODUCT DATABOOK 1996/1997
ULTRA 27-LINE, PLUG AND PLAY SCSI TERMINATOR
PRODUCTION DATA SHEET
TERM POWER
BLOCK DIAGRAM
CURRENT
BIASING
CIRCUIT
24mA CURRENT
LIMITING CIRCUIT
2.85V
LX5122
DATA OUTPUT
PIN DB(0)
1.4V
1 OF 27 CHANNELS
FUNCTIONAL DESCRIPTION
Cable transmission theory suggests that in order to optimize
signal speed and quality, the termination should act both as
an ideal voltage reference when the line is released (de-asserted)
and as an ideal current source when the line is active (asserted).
Common active terminators, which consist of Linear Regulators
in series with resistors (typically 110Ω), are a compromise. As
the line voltage increases, the amount of current decreases
POWER UP / POWER DOWN FUNCTION TABLE
DISC1 DISC2 W1 W2 N1 T1-T18
L
H
DC DC DC Enabled
H
L
DC DC DC Disabled
H
H
DC DC DC Disabled
L
L
H
H
H Enabled
L
L
H
H
L Enabled
L
L
H
L
H Enabled
L
L
H
L
L Disabled
L
L
L
H
H Enabled
L
L
L
H
L Disabled
L
L
L
L
H Disabled
L
L
L
L
L Disabled
linearly by the equation V = I * R. The UltraMAX LX5122, with
its unique new architecture, applies the maximum amount of
current regardless of line voltage until the termination high
threshold (2.85V) is reached.
Acting as a near ideal line terminator, the LX5122 closely
reproduces the optimum case when the device is enabled. To
enable the device the DISC1 and DISC2 pins must be driven
per the above table. During this mode of operation,
quiescent current is 12mA and the device will
T19-T27 respond to line demands by delivering 24mA on
assertion and by imposing 2.85V on de-assertion.
Disabled
Enabled
Disabled
Enabled
Enabled
Disable mode places the device in a sleep state,
where a meager 150µA of quiescent current is
consumed. Additionally, all outputs are in a Hi-
Z (impedance) state. Sleep mode can be used
for power conservation or to completely eliminate
the terminator from the SCSI chain.
Enabled
An additional feature of the LX5122 is its com-
Enabled patibility with active negation drivers.
Enabled
Enabled
Disabled
Disabled
Copyright © 1999
Rev. 1.0 6/99
3
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