LX5219CPW MICROSEMI [Microsemi Corporation], LX5219CPW Datasheet - Page 4

• Manufacturer Part Number: LX5219CPW
• Description: ULTRA 9 - CHANNEL SCSI TERMINATOR
• Manufacturer: MICROSEMI [Microsemi Corporation]

LX5219
4
Cable transmission theory suggests to optimize signal speed
and quality, the termination should act both as an ideal voltage
reference when the line is released (deasserted) 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
110 ), are a compromise. As the
line voltage increases, the amount
of current decreases linearly by the
equation V = I * R. The LX5219,
with its unique new architecture
applies the maximum amount of
current regardless of line voltage
until the termination high thresh-
old (2.85V) is reached.
reproduces the optimum case when the device is enabled.
To enable the device the Disable Pin must be pulled logic
High or left Open. During this mode of operation, quiescent
current is 6mA and the device will respond to line demands
Acting as a near ideal line terminator, the LX5219 closely
DISABLE
PIN
1.4V
TERM POWER
THERMAL
LIMITING
CIRCUIT
P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7
U L T R A 9 - C
P
P
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
OWER
(LX5219)
Disable
Open
H
L
U
B L O C K D I A G R A M
P
H A N N E L
/ P
OWER
CURRENT
BIASING
CIRCUIT
Outputs
D
Enabled
Enabled
OWN
HI Z
S C S I T
D
by delivering 24mA on assertion and by imposing 2.85V on
deassertion. In order to disable the device, the Disable pin
must be driven logic Low. This mode of operation places
the device in a sleep state where a meager 275µA of quiescent
current is consumed. Additionally, all outputs are in a Hi-Z
LX5219 has been optimized to have only 3pF of capacitance
per output in the sleep state.
active negation drivers. The device handles up to 60mA of
sink current for drivers which exceed the 2.85V output high.
A T A
An additional feature of the LX5219 is its compatibility with
F
UNCTION
E R M I N A T O R
S
Quiescent
Current
H E E T
275µA
6mA
6mA
T
ABLE
LIMITING CIRCUIT
24mA CURRENT
2.85V
(impedance) state. Sleep mode can
be used for power conservation or
to completely eliminate the termi-
nator from the SCSI chain. In the
second case, termination node ca-
pacitance is important to consider.
The terminator will appear as a
parasitic distributed capacitance on
the line, which can detract from bus
performance. For this reason, the
1 OF 9 CHANNELS
DATA OUTPUT
PIN DB(0)
UltraMAX
Copyright © 1998
Rev. 1.8
3/98