Digitally-tuned oscillator including a self-calibrating RC oscillator circuit
First Claim
Patent Images
1. A digitally-tuned oscillator (DTO) comprising:
- a switched-capacitor digital to analog converter (DAC); and
an RC oscillator coupled to the switched capacitor DAC.
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Abstract
A digitally-tuned oscillator (DTO) includes a digital-to-analog converter (DAC) and an RC oscillator. The RC oscillator includes an RC circuit for forming a time constant equal to the RC product. However, this RC time constant is not used in the manner of a typical RC network to set the frequency of oscillation. Instead, the RC oscillator disclosed herein includes a separate oscillator, such as a voltage-controlled oscillator (VCO), and uses the RC time constant to compare with the oscillator-generated period and to adjust the frequency of the overall RC oscillator circuit in accordance with the comparison. The RC oscillator is self-calibrating.
99 Citations
26 Claims
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1. A digitally-tuned oscillator (DTO) comprising:
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a switched-capacitor digital to analog converter (DAC); and an RC oscillator coupled to the switched capacitor DAC. - View Dependent Claims (2, 3, 4, 5)
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6. A digitally-tuned oscillator (DTO) comprising:
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a switched-capacitor digital to analog converter (DAC); and an RC oscillator coupled to the switched capacitor DAC, the RC oscillator including; an RC network for setting an RC time constant; a core oscillator for generating a timing signal at a controlled frequency having an input terminal for controlling frequency of the core oscillator; a comparator coupled to the RC network and the core oscillator for comparing an indicator of the controlled frequency to an indicator of the RC time constant; and means responsive to the comparator for adjusting the frequency of the core oscillator. - View Dependent Claims (7, 8, 9, 10, 11)
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12. A digitally-tuned oscillator (DTO) comprising:
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a switched-capacitor digital to analog converter (DAC); and an RC oscillator coupled to the Switched capacitor DAC, the RC oscillator including; a first input terminal coupled to an input resistance R; a second input terminal coupled to an input capacitance C; a ramp and hold circuit coupled to the first and second input terminals for establishing a time constant proportional to a multiplication product of the input resistance R and the input capacitance C; an oscillator generating an output timing signal having a period of oscillation established by a control input signal; a comparator coupled to the ramp and hold circuit and to the oscillator to compare an integer multiple of periods of the output timing signal to the time constant; and a control signal generator coupled to the oscillator and responsive to the comparator by generating an incremental signal to the control input signal to adjust the period of oscillation. - View Dependent Claims (13, 14, 15, 16, 17)
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18. A digitally-tuned oscillator (DTO) comprising:
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a switched-capacitor digital to analog converter (DAC); and an RC oscillator coupled to the switched capacitor DAC, the RC oscillator including; a resistance R; a capacitance C; time constant means coupled to the resistance R and the capacitance C for establishing a time constant proportional to the multiplication product of the resistance R and the capacitance C; an oscillator means for generating a timing signal having a period of oscillation established by a control signal; a comparator means coupled to the time constant means and coupled to the oscillator means for comparing an integer multiple of periods of the timing signal to the time constant; and means coupled to the oscillator means and responsive to the comparator means for generating a control signal to adjust the period of oscillation of the timing signal, the control signal being generated by incrementing a previous version of the control signal. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26)
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Specification