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Synthesizers tout 0.37-5.79GHz frequency range

Posted: 03 Oct 2011 ?? ?Print Version ?Bookmark and Share

Keywords:frequency synthesizer? phase-locked loop? VCO?

Linear Technology Corp. has rolled out a range of integer-N frequency synthesizers with integrated VCO. The LTC6946 features -226dBc/Hz normalized closed-loop in-band phase noise, -274dBc/Hz normalized in-band 1/f noise and -103dBc spurious output.

In a typical 900MHz application, these performance attributes help to achieve a closed-loop phase noise of -100dBc/Hz at 1kHz offset. The device is available in three frequency options. The LTC6946-1 tunes from 2.240-3.740GHz, the LTC6946-2 from 3.080-4.910GHz and the LTC6946-3 covers 3.840-5.790GHz. In addition, each part has an on-chip output divider that is programmable from 1 through 6 to extend frequency coverage as low as 373MHz.

This family of devices integrates low noise 5.7GHz phase-locked loop (PLL) that includes a reference divider and phase-frequency detector (PFD) with phase-locked indicator. According to Linear Tech, the synthesizers have ultralow noise charge pump and integer feedback divider to attain very low noise PLL operation, said the company. The PLL circuit is tightly coupled to a low noise VCO, as well as, internal self-calibration to ensure optimum VCO resonator tuning for best phase noise performance, added the company. The VCO requires no external components. The on-chip SPI compatible bidirectional serial port allows frequency tuning and control, and read back of register and loop status information.


The synthesizers feature ultralow noise charge pump.


The LTC6946 includes a reference divider and phase-frequency detector.

The low phase noise and spurious capabilities of this family of frequency synthesizers enhance the performance of multiband base stations supporting LTE, W-CDMA, UMTS, CDMA, GSM and WiMAX standards, noted Linear Tech. Its high frequency capability also supports point-to-point broadband wireless access, military, avionics, and high performance test and measurement applications.

The PLLWizard comprehensive PC-based design tool software is available to facilitate interactive control and interface with the LTC6946's evaluation board. Designers can perform simulations and optimization with the software, and then interactively verify their designs on the actual demonstration circuit. The PLLWizard design tool is available free from Linear Tech's website.

All versions of the LTC6946 are specified over the full case temperature range from -40C to 105C. The products are available in 4 x 5mm, 28-lead plastic QFN package. Prices start at $5.75 each in 1,000-piece quantities.

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