
U LT R A 9 - C
H A N N E L
S C S I T
E R M I N A T O R
LX5111/5112
P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7
Copyright 1997
Rev. 1.1 12/97
4
P
R O D U C T I O N
D
A T A
S
H E E T
UltraMAX
B L O C K D I A G R A M
F U N C T I O N A L D E S C R I P T I O N
THERMAL
LIMITING
CIRCUIT
TERM POWER
CURRENT
BIASING
CIRCUIT
1.4V
DISCONNECT (5111)
DISCONNECT (5112)
24mA CURRENT
LIMITING CIRCUIT
DATA OUTPUT
PIN DB(0)
2.85V
1 OF 9 CHANNELS
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.
Acting as a near ideal line terminators, the LX5111/5112
closely reproduce the optimum case when the devices are
enabled. To enable the device the DISCONNECT pin
(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
2.85V on deassertion. In order to disable the device, the
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
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
this reason, the LX5111/5112 have been optimized to have only
3pF of capacitance per output in the sleep state.
An additional feature of the LX5111/5112 IC's are their
compatibility with active negation drivers. These devices handle
up to 60mA of sink current for drivers which exceed the 2.85V
output high.
UltraMAX is a trademark of Linfinity Microelectronics Inc.
PRODUCTION DATA - Information contained in this document is proprietary to Linfinity, and is current as of publication date. This document
Outputs
Quiescent
Current
H
L
L
H
Enabled
HI Z
HI Z
6mA
275μA
275μA
Open
Open
LX5111
DISCONNECT
LX5112
DISCONNECT
P
OWER
U
P
/ P
OWER
D
OWN
F
UNCTION
T
ABLE