lx5112 Microsemi Corporation, lx5112 Datasheet - Page 4

• Manufacturer Part Number: lx5112
• Description: Ultra 9 - Channel Scsi Terminator
• Manufacturer: Microsemi Corporation

LX5111/5112
4
DISCONNECT (5111)
DISCONNECT (5112)
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 LX5111/5112, with
their unique new architecture ap-
plies the maximum amount of
current regardless of line voltage
until the termination high threshold
(2.85V) is reached.
closely reproduce the optimum case when the devices are
enabled.
(DISCONNECT pin for the LX5112) must be pulled logic High
(logic Low for the LX5112). During this mode of operation,
quiescent current is 6mA and the devices will respond to line
demands by delivering 24mA on assertion, and by imposing
Acting as a near ideal line terminators, the LX5111/5112
To enable the device the DISCONNECT pin
1.4V
TERM POWER
PRODUCTION DATA - Information contained in this document is proprietary to Linfinity, and is current as of publication date. This document
may not be modified in any way without the express written consent of Linfinity. Product processing does not necessarily include testing of
all parameters. Linfinity reserves the right to change the configuration and performance of the product and to discontinue product at any time.
P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7
THERMAL
LIMITING
CIRCUIT
U L T R A 9 - C
DISCONNECT DISCONNECT
P
LX5111
Open
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
H
L
UltraMAX is a trademark of Linfinity Microelectronics Inc.
U
B L O C K D I A G R A M
P
H A N N E L
/ P
LX5112
Open
H
OWER
L
CURRENT
D
BIASING
CIRCUIT
S C S I T
OWN
D
2.85V on deassertion.
DISCONNECT pin (DISCONNECT pin for the LX5112) must be
driven logic Low (logic High for the LX5112). This mode of
operation places the devices in a sleep state where a meager
275µA of quiescent current is consumed. Additionally, all outputs
Outputs
Enabled
this reason, the LX5111/5112 have been optimized to have only
3pF of capacitance per output in the sleep state.
compatibility with active negation drivers. These devices handle
up to 60mA of sink current for drivers which exceed the 2.85V
output high.
A T A
An additional feature of the LX5111/5112 IC's are their
HI Z
HI Z
F
UNCTION
E R M I N A T O R
S
Quiescent
H E E T
Current
275µA
275µA
T
6mA
ABLE
LIMITING CIRCUIT
24mA CURRENT
In order to disable the device, the
2.85V
are in a Hi-Z (impedance) state.
Sleep mode can be used for power
conservation or to completely elimi-
nate the terminator from the SCSI
chain. In the second case, termi-
nation node capacitance is impor-
tant to consider. The terminators
will appear as a parasitic distributed
capacitance on the line, which can
detract from bus performance. For
1 OF 9 CHANNELS
UltraMAX
DATA OUTPUT
PIN DB(0)
Copyright © 1997
Rev. 1.1
12/97