Circuits, systems, and methods for a voltage controlled oscillator with coarse, fine, and center tuning

Abstract

Circuits, systems, and methods for generating a variable oscillator output. The circuits generally comprise a capacitor configured to receive first and second currents of a first polarity (e.g., charging currents) and a third current of a second polarity opposite to the first polarity (e.g., a discharge current). The circuit further comprises a first circuit configured to receive a bias input, a second circuit configured to receive a coarse control input, and a third circuit configured to receive a fine control input. The first circuit is further configured to provide the first current in response to the bias input. The second circuit is further configured to provide the second current in response to the coarse control input, such that the second current generally has a magnitude of from zero to a multiple of the magnitude of the first current. The third circuit is further configured to provide the third current when the capacitor has a voltage that passes a threshold voltage determined by the fine control input. The present invention advantageously provides for producing a variable oscillator output over a broad range with the coarse control input, while also having low gain with the fine control input. The present invention is also advantageously suitable for standard integrated circuit manufacturing processes because the bias input can be adjusted to compensate for process variations.