ZLNB2002

DUAL TONE and POLARITY SWITCH LNB MULTIPLEX CONTROLLER ISSUE 1- NOVEMBER 1998 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 e ase de sign for this situation, each polarisation input of the ZLNB200X has a second threshold set at 9.5V. An input voltage below this threshold indicates ZLNB2001 ZLNB2002 ZLNB2003 ZLNB2004 "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 superimp...