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ZLNB2003Q16

DUAL TONE and POLARITY SWITCH LNB MULTIPLEX CONTROLLER

Zetex => Diodes 

DUAL TONE and POLARITY SWITCH LNB

MULTIPLEX CONTROLLER

ISSUE 1- NOVEMBER 1998

ZLNB2001 ZLNB2002

ZLNB2003 ZLNB2004

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

ease design for this situation, each

polarisation input of the ZLNB200X has a

second threshold set at 9.5V. An input

voltage below this threshold indicates

"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

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