DEVICE DESCRIPTION
The ZLNB2012 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, Quad and multiple feed
Universal LNBs, replacing many discrete components
to save both manufacturing cost and PCB size whilst
improving reliability.
The two highly accurate polarisation control inputs of
the ZLNB2012 have a nominal threshold of 14.25V and
to meet the required demanding needs from some
broadcasters they have a switching range of 14.0V to
14.5V. 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.
Multi Feed LNBs can be called to operate with one or
more of their controlling receivers powered
down/disconnected, with attendant cable mismatch
problems. To ease design for this situation, each
polarisation input of the ZLNB2012 has a second
threshold set at 9V. An input voltage below this
threshold indicates“ receiver not present”, and
switches the relevant control channels high. This logic
output can be used to disable the associated downfeed
driver, eliminating any problems due to cable
mismatch.
FEATURES
·
Dual polarisation and tone switch
·
Reduced Cost Solution, only 2 external components
per channel
·
Close tolerance (14-14.5V) and temperature
compensated polarisation switch
·
Multiplexer IC direct drive
·
Tone and pol. Outputs are TTL, CMOS, Pin diode and
IF amp capable
·
Transient resistant inputs
·
Includes Receiver-Off detector
·
User adjustable filter centre frequency and
bandwidth
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 ZLNB2012 includes a separate tone
detector for each channel. Control of detector
bandwidth and sensitivity is provided using an
external resistor and capacitor for each channel. The
tone detector has been designed give excellent
rejection of low frequency control signals and
DiSEqC™ tone bursts.
The ZLNB2012 has been specifically designed to
minimise the solution cost whilst being flexible. The
ZLNB2012 only requires two external components per
channel to give full user control and functionality. The
ZLNB2012 also includes complimentary outputs so
that it can directly drive many multiplexer IC’s without
the need of an inverter. Any unused outputs can be left
open circuit without any effect to the remaining circuits
operation Polarisation switch and tone detector
outputs can directly drive TTL and CMOS logic, pin
diodes, IF-amp supply switching and multiplexer IC’s.
The ZLNB2012 operates from a single supply which
can be anything from 5-8V. Its quiescent current is
typically only 9mA and this does not change
significantly with load or logic state. It is available in the
space saving QSOP16 surface mount package.
·
Low frequency and DiSEqC control signals
rejection
·
Eliminates many close tolerance discrete
components
·
Wide supply operating range
·
Low quiescent current
APPLICATIONS
·
Twin Universal LNB’s
·
Quad Universal LNB’s
·
Multi Feed Universal LNB’s
·
LNB switch boxes
PROVISIONAL ISSUE A - OCTOBER 2001
1
DUAL TONE AND POLARITY SWITCH
LNB MULTIPLEX CONTROLLER
ZLNB2012
