Improved system performance with built-in VCO


October 19, 2011 -- Linear Technology Korea (CEO Hong Sa-kwak, www.linear.com) announced the introduction of the first device (product name: LTC6946) in its family of high-performance integer-N frequency synthesizers with an integrated VCO. This product provides -226 dBc/Hz normalized closed-loop in-band phase noise, excellent -274 dBc/Hz normalized in-band 1/f noise, and an industry-leading spurious output of -103 dBc. In typical 900 MHz applications, these performances play a significant role in achieving -100 dBc/Hz closed-loop phase noise at a 1 kHz offset.

This product is available in three frequency options. The LTC6946-1 is adjustable from 2.240 GHz to 3.740 GHz, the LTC6946-2 from 3.080 GHz to 4.910 GHz, and the LTC6946-3 from 3.840 GHz to 5.790 GHz. In addition, each component is equipped with an on-chip output divider programmable from 1 to 6 to extend frequency coverage to a low range of 373 MHz.

This new product family incorporates a low-noise 5.7GHz phase-locked loop (PLL), which includes a reference divider, a phase-frequency detector (PFD) phase-locked indicator, an ultra-low noise charge pump, and an interga feedback divider for implementing very low-noise PLL operation. The PLL circuit features internal self-compensation and is tightly coupled to the low-noise VCO, allowing for optimal VCO resonator tuning to achieve the best phase-noise performance. This VCO is also characterized by the fact that it does not require external components. The on-chip SPI-compatible bidirectional serial port enables frequency tuning and control, as well as readback functions for register and loop status information.

This family of frequency synthesizers features low face noise and spurious capabilities, which can improve the performance of multi-band base stations supporting LTE, W-CDMA, UMTS, CDMA, GSM, and WiMAX standards. Additionally, high-frequency operation is possible, supporting point-to-point broadband wireless access, military, aviation, and high-performance instrumentation applications.

PLLWizard™ comprehensive PC-based design tool software is provided for interactive control and interfacing with the LTC6946 evaluation board. Designers can perform simulations and optimizations with PLLWizard software and then interactively verify their designs on a physical demo board. The PLLWizard design tool software is available for free on the Linear Technology website at www.linear.com/synthesizers.

All versions of the LTC6946 can operate over a full case temperature range of -40°C to 105°C. The products are available in a 4mm x 5mm, 28-pin plastic QFN package. Pricing starts at $5.75 per unit for 1,000 units, and orders are available immediately.