Variable-path-length voltage-controlled oscillator circuit
First Claim
1. A programmable logic device that is proarammed using a programmable logic device programmer comprising:
- a series of linked inverter stages having controllable delay times;
a path length selection circuit that forms a ring oscillator having a selected path length from the inverter stages in response to path length configuration data;
an oscillator output connected to the ring oscillator that provides an output signal with a frequency determined by the selected path length and by the delay times of the inverter stages; and
programmable memory that is configured to store the path length configuration data and that is programmed with the path length configuration data using the programmable logic device programmer.
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Accused Products
Abstract
A variable-path-length voltage-controlled oscillator circuit is provided. The oscillator circuit has a ring oscillator formed from a series of voltage-controlled inverter stages. The path length (i.e., the number of inverter stages) in the ring is selected based on path length configuration data stored in memory. The selected path length determines the nominal or center frequency of operation of the ring oscillator. The output frequency of the oscillator circuit is voltage-tuned about this center frequency by varying the delay of each inverter stage in the ring oscillator path. Various types of voltage-controlled inverter stages may be used, including current-starved inverter stages, variable-capacitive-load inverter stages, and differential-delay inverter stages. The voltage-controlled oscillator circuit may be used in a phase-locked loop on a programmable logic device for frequency synthesis or to eliminate clock skew.
88 Citations
12 Claims
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1. A programmable logic device that is proarammed using a programmable logic device programmer comprising:
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a series of linked inverter stages having controllable delay times; a path length selection circuit that forms a ring oscillator having a selected path length from the inverter stages in response to path length configuration data; an oscillator output connected to the ring oscillator that provides an output signal with a frequency determined by the selected path length and by the delay times of the inverter stages; and programmable memory that is configured to store the path length configuration data and that is programmed with the path length configuration data using the programmable logic device programmer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A programmable logic device that is programmed using a programmable logic device programmer comprising:
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a series of linked inverter stages each having an input for a control voltage and each having a delay time controlled by the magnitude of the control voltage; a path length selection circuit connected to the linked inverter stages to form a ring oscillator having a selected one of various path lengths in response to path length configuration data; a ring oscillator output that provides an output signal at a frequency determined by the selected path length and the magnitude of the control voltage; and programmable memory that is configured to store the path length configuration data and that is programmed with the path length configuration data using the programmable logic device programmer. - View Dependent Claims (12)
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Specification