DUAL TONE and POLARITY SWITCH LNB
MULTIPLEX CONTROLLER
ISSUE 1- NOVEMBER 1998
DEVICE DESCRIPTION
The ZLNB200X dual polarisation and tone
switch controller is one of a wide range of
satellite receiver LNB support circuits
available from Zetex. It features two
completely independent channels, each
providing logic outputs to control LNB
polarisation selection, local oscillator
selection and downfeed disable. It is
intended for use in Twin Universal LNBs,
replacing many discrete components to save
both manufacturing cost and PCB size whilst
improving reliability.
The two polarisation control inputs of the
ZLNB200X have a nominal threshold of
14.75V. The threshold is temperature
compensated to minimise drift. Each
features a low and stable input current that
enables transient protection to be achieved
with the addition of only a single resistor per
channel.
Twin Universal LNBs can be called to
operate with one of their controlling
receivers powered down/disconnected, with
attendant cable mismatch problems. To
e ase de sign for this situation, each
polarisation input of the ZLNB200X has a
second threshold set at 9.5V. An input
voltage below this threshold indicates
ZLNB2001 ZLNB2002
ZLNB2003 ZLNB2004
"receiver not present", switching the
channels Enable pin low. This logic output
can be used to disable the associated
downfeed driver, eliminating any problems
due to cable mismatch.
Universal LNB local oscillator selection is
achieved by detection of a low level AC
voltage superimposed on the polarisation
control voltage. To facilitate this function,
the ZLNB200X includes a separate tone
detector for each channel. Full control of
detector bandwidth and sensitivity is
provided using two external resistors and
capacitors. In the ZLNB2003/4, additional
control of tone switch delays is provided to
assist with the rejection of low frequency
control signals intended for other systems.
Polarisation switch and tone detector
outputs can source and sink 10mA making
them suitable to drive TTL and CMOS logic,
pin diodes and for IF-amp supply switching.
The ZLNB200X operates from a single
supply which can be anything from 5-10V. Its
quiescent current is typically only 6mA and
this does not change significantly with load
or logic state. It is available in the space
saving QSOP16 surface mount package.
FEATURES
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Dual polarisation switch
Temperature compensated polarisation
switch threshold
Transient resistant inputs
Includes Receiver-Off detector
Dual tone switch
User adjustable filter centre frequency
and bandwidth
User adjustable tone switching delays
(ZLNB2003/4 only)
Tone and pol. outputs TTL, CMOS, Pin
diode and IF amp capable
Receiver-Off detector TTL and CMOS
compatible
Wide supply operating range
Low quiescent current
Few external components
Eliminates many discrete components
APPLICATIONS
Twin Universal LNB
Twin Universal IF switch boxes
LNB switch boxes
81
ZETEX [ ZETEX SEMICONDUCTORS ]
