ZLNB2006

The ZLNB2006/09/10 group of dual polarisation and tone switch controller are part of a wide range of satellite receiver LNB support circuits available from Zetex. Each part features two completely independent channels, each providing logic outputs to control LNB polarisation selection, local oscillator selection and the ZLNB2009/10 also provides downfeed disable. They are intended for use in Twin Universal and Quad LNBs, replacing many discrete components to save both manufacturing cost and PCB size whilst improving reliability.

The two polarisation control inputs of the ZLNB2006/09/10 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.

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 ZLNB2006 has a second threshold set at 9.5V. An input voltage below this threshold indicates "receiver not present", switching the relevant control channels high. 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 ZLNB2006/09/10 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 ZLNB2006/9, 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 ZLNB2006 suitable to drive TTL and CMOS logic, pin diodes and IF-amp supply switching.

The ZLNB2006/09/10 operates from a single supply which can be anything from 5-10V. Their quiescent current is typically only 6mA and this does not change significantly with load or logic state. They are available in the space saving QSOP16 or QSOP20 surface mount package.