LX5121CDB Microsemi Corporation, LX5121CDB Datasheet - Page 3

• Manufacturer Part Number: LX5121CDB
• Description: ULTRA 27-LINE/ PLUG AND PLAY SCSI TERMINATOR
• Manufacturer: Microsemi Corporation

UltraMAX
Copyright © 1999
Rev. 1.0
DISC1
Cable transmission
theory suggests that in
order to optimize sig-
nal speed and quality,
the
should act both as an
ideal voltage refer-
ence when the line is
released (de-asserted)
and as an ideal current
source when the line
is active (asserted).
Common active termi-
nators, which consist
of Linear Regulators in
series with resistors
(typically 110 ), are a
compromise. As the
line voltage increases, the amount of current decreases linearly
by the equation V = I * R. The UltraMAX LX5121, with its
unique new architecture, applies the maximum amount of
current regardless of line voltage until the termination high
threshold (2.85V) is reached.
5/99
Acting as a near ideal line terminator, the LX5121 closely
V
CC
termination
V
CC
DISC2
1.4V
DISC1
TERM POWER
H
H
H
H
H
H
H
H
H
L
L
P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7
ULTRA 27-L
P
DISC2
P
H
H
H
H
H
H
H
H
H
R O D U C T I O N
F U N C T I O N A L D E S C R I P T I O N
L
L
OWER
I N E
U
B L O C K D I A G R A M
P
W1
, P
DC
DC
DC
H
H
H
H
L
L
L
L
/ P
L U G A N D
OWER
W2
DC
DC
DC
H
H
H
H
L
L
L
L
D
CURRENT
BIASING
OWN
D
CIRCUIT
P
escent 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.
active negation drivers.
A T A
LAY
An additional feature of the LX5121 is its compatibility with
N1
DC
DC
DC
H
H
H
H
L
L
L
L
F
UNCTION
SCSI T
S
Disabled
Disabled
Disabled
Disabled
Disabled
Disabled
Enabled
Enabled
Enabled
Enabled
Enabled
T1-T18
H E E T
T
ERMINATOR
ABLE
LIMITING CIRCUIT
24mA CURRENT
Disabled
Disabled
Disabled
Disabled
T19-T27
Enabled
Enabled
Enabled
Enabled
Enabled
Enabled
Enabled
2.85V
1 OF 27 CHANNELS
reproduces the opti-
mum case when the
device is enabled. To
enable the device the
DISC1 and DISC2 pins
must be driven per the
above table.
this mode of operation,
quiescent current is
12mA and the device
will respond to line de-
mands by delivering
24mA on assertion and
by imposing 2.85V on
de-assertion.
mode places the device
in a sleep state, where
a meager 150µA of qui-
LX5121
DATA OUTPUT
PIN DB(0)
Disable
During
3