Controllers cut satellite receivers down to size

Satellite LNB controllers require just three external components to function - 10 fewer than alternative single universal LNBs and 20 fewer than typical C-band LNB designs.

Integrating all bias, control and power management functions into a single chip solution, the latest satellite low noise block (LNB) controllers from Zetex Semiconductors help to achieve LNB size reductions of up to 30%.

Offered in 16-pin 3 x 3 and 4 x 4mm QFN packages, the controllers require just three external components to function, 10 fewer than alternative single universal LNBs and 20 fewer than typical C-band LNB designs.

Three LNB controllers have been introduced: the ZXNB4100 and ZXNB4200 for single universal LNBs (for respectively negative and zero volt bias FET switching topologies) and the ZXNB2200 for C-band LNB designs.

By reducing PCB size and routing complexity, component counts and the size of the aluminium housing, the new controllers are expected to have a significant impact on the overall material cost of future generations of LNBs.

At the heart of LNB designs, the ZXNB controllers provide biasing for up to three GaAs FET LNA stages and an active mixer.

To optimise system performance the drain current of LNA FETs and the active mixer is user selectable via an external reference resistor.

The onboard voltage detector allows the controller to enable the required polarisation channel, while a 22kHz tone detector with integrated filter and signal rejection handles switching between high and low band oscillators.

By bringing the voltage regulator into the LNB controller chip for the very first time, the ZXNB controllers are "self-powering" and able to provide a temperature compensated high current output voltage, sufficient to power all other parts of the LNB circuit, such as the IF amplifier stages.

The integration of power management functions means the LNB controller is also able to protect against overload, over temperature and installation errors.

Zetex Semiconductors is supporting the new product introductions with a ZXNB4200 based reference design for a single universal LNB, by far the most common and price sensitive type of LNB.

The ZXNB4100 and ZXNB4200 for single universal LNBs are priced at US $1.78 in 1000-unit quantities (3 x 3mm QFN package) and the ZXNB2200 for C-band LNBs is priced at US $1.63 in 1000-unit quantities.

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