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