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Synthesizer touts -226dBc/Hz in-band phase noise

Posted: 21 Dec 2011 ?? ?Print Version ?Bookmark and Share

Keywords:broadband wireless? synthesizer? charge pump?

Linear Technology Corp. has released a 6GHz integer-N frequency synthesizer with -226dBc/Hz normalized closed-loop in-band phase noise. The LTC6945 also features -274dBc/Hz normalized in-band 1/f noise, a wideband phase noise floor of -157dBc/Hz and -102dBc spurious output. In a normal 900MHz application, these performance attributes enable a closed-loop phase noise of -100dBc/Hz at 1kHz offset, added the company.

The LTC6945 is made to work in conjunction with an external low noise VCO up to 6GHz. In addition, the device has an on-chip output divider that is programmable from 1 through 6 to extend the tuning frequency coverage to as low as 350MHz, noted Linear Tech.


The LTC6945 comprises a reference buffer and a reference divider.

The device comprises a low noise reference buffer, a reference divider, phase-frequency detector (PFD) with phase-locked indicator, an ultralow noise programmable charge pump and an integer feedback divider to attain very low noise PLL operation, stated the company. The on-chip SPI-compatible bidirectional serial port allows frequency tuning and control, and read back of the register and loop status information.

The low phase noise and spurious capabilities of the LTC6945 enhance the performance of RF and wireless equipment of all types, including multiband base stations supporting LTE, WCDMA, UMTS, CDMA, multicarrier GSM and WiMAX standards. Its wide frequency range also supports point-to-point broadband wireless access, military, avionics and high performance test and measurement applications, Linear Tech stated.

The PLLWizard PC-based design tool software is available to facilitate interactive control and to interface with the LTC6945's evaluation board. Designers can perform simulations and optimization with the PLLWizard software, and then interactively verify their designs on the actual demonstration circuit.

The LTC6945 operates from -40C to 105C. It is available from stock in a 4 x 5mm, 28-lead plastic QFN package, priced starting at $4.95 each in 1,000-piece quantities.

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