ZLNB2012

ZLNB2012 DUAL TONE AND POLARITY SWITCH LNB MULTIPLEX CONTROLLER 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 mi...