National Semiconductor Corporation

Kim Yeow Wong

David Lindsay Broughton

Jeffrey Mark Huard

A circuit and method for providing a tunable capacitance for a voltage control oscillator (VCO) in which at least one P-N junction varactor and at least one metal oxide semiconductor (MOS) accumulation-mode varactor are effectively coupled and tuned in parallel, thereby providing a net tunable capacitance with which the VCO will realize an optimal combination of quality factor, phase noise, and gain characteristics.

Tunable capacitance circuit for voltage control oscillator

A method for internally resetting a charge pump is provided that includes receiving an up signal and a down signal simultaneously. A feedback signal is generated based on the up and down signals. The feedback signal is provided internally to the charge pump. The charge pump is reset based on the feedback signal.

Method and system for internally resetting a charge pump

Oscillator control circuitry for a phase lock loop, including phase detection circuitry, control signal generator circuitry, bias control circuitry and charge pump circuitry. The control signal generator circuitry introduces specific and distinct time delays to the phase signals from the phase detection circuitry representing the phase difference between the reference and oscillator output signals. These time delays cause the bias control circuitry to enable and disable the output charge pump circuitry slightly before and after, respectively, those time intervals during which an output source (&ldquo;pump up&rdquo;) or sink (&ldquo;pump down&rdquo;) current is needed to drive the oscillator via the loop filter. This produces charge pump circuitry output signals with significantly faster rise and fall times and shorter pulse widths, thereby resulting in a charge pump output signal with higher SNR and reduced spurious signal energy.

Growing community of inventors

Renton, WA, United States of America

Kim Yeow Wong