鈩?/div>
DESCRIPTION
Intended for analog and digital satellite receivers,
the LNBK20D2 is a monolithic linear voltage
regulator, assembled in SO-20, specifically
designed to provide the powering voltages and the
interfacing signals to the LNB downconverter
situated in the antenna via the coaxial cable. It has
the same functionality of the LNBP1X and
LNBP20 series, at a reduced output current
capability. Since most satellite receivers have two
antenna ports, the output voltage of the regulator
is available at one of two logic-selectable output
pins (LNBA, LNBB). When the IC is powered and
put in Stand-by (EN pin LOW), both regulator
outputs are disabled to allow the antenna
downconverters to be supplied/controlled by
others satellite receivers sharing the same coaxial
lines. In this occurrence the device will limit at 3
mA (max) the backward current that could flow
from LNBA and LNBB output pins to GND.
For slave operation in single dish, dual receiver
systems, the bypass function is implemented by
an electronic switch between the Master Input pin
鈩?/div>
SO-20
(MI) and the LNBA pin, thus leaving all LNB
powering and control functions to the Master
Receiver. This electronic switch is closed when
the device is powered and EN pin is LOW.
The regulator outputs can be logic controlled to be
13 or 18 V (typ.) by mean of the VSEL pin for
remote controlling of LNBs. Additionally, it is
possible to increment by 1V (typ.) the selected
voltage value to compensate the excess voltage
drop along the coaxial cable (LLC pin HIGH).
In order to reduce the power dissipation of the
device when the lowest output voltage is selected,
the regulator has two Supply Input pins V
CC1
and
V
CC2
. They must be powered respectively at 16V
(min) and 23V (min), and an internal switch
automatically will select the suitable supply pin
according to the selected output voltage. If
adequate heatsink is provided and higher power
losses are acceptable, both supply pins can be
powered by the same 23V source without
affecting any other circuit performance.
The ENT (Tone Enable) pin activates the internal
oscillator so that the DC output is modulated by a
卤0.3 V, 22KHz (typ.) square wave. This internal
oscillator is factory trimmed within a tolerance of
卤2KHz, thus no further adjustments neither
external components are required.
A burst coding of the 22KHz tone can be
accomplished thanks to the fast response of the
ENT input and the prompt oscillator start-up. This
helps designers who want to implement the
DiSEqC protocols (*).
In order to improve design flexibility and to allow
implementation of newcoming LNB remote control
standards, an analogic modulation input pin is
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