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US 7,248,123 B2Granted
Phase locked loop with floating capacitor boost circuit
AssigneeCeva Services Limited
InventorJohn M. Horan
Life of this patent
Estimating the term…
Abstract
Charge from a charge pump of a PLL is dumped to a loop filter of the PLL. The dumped charge is temporarily stored in a capacitor, between the charge pump and the loop filter. A voltage of the capacitor is shifted, while temporarily storing the dumped charge. Other embodiments are also described and claimed.
Claims18
A method for operating a phase locked loop (PLL) circuit, comprising:
- dumping charge from a charge pump to a loop filter of the PLL;
- temporarily storing the dumped charge in a capacitor between the charge pump and the loop filter;
- and
- shifting a voltage of the capacitor while temporarily storing the dumped charge, by floating the capacitor.
1 more element
A phase locked loop (PLL) circuit, comprising:
- a voltage controlled oscillator (VCO);
- a phase detector having a charge pump with an output coupled to an input of the VCO;
- a loop filter coupled between the phase detector and the VCO;
- and
- a boost circuit coupled between the phase detector and the VCO input, the boost circuit having switch circuitry to (a) alternatively couple a capacitor to the charge pump output in a first state and to the VCO input in a second state, and (b) alternatively couple a voltage in series with the capacitor in the second state and remove the voltage in the first state.
2 more elements
A phase locked loop (PLL) circuit, comprising:
- means for dumping charge onto an input control node of a voltage controlled oscillator (VCO) of the PLL in response to detecting a phase difference between a reference signal and a feedback signal derived from an output of the VCO;
- and
- means for boosting the input control node voltage without using said dumping means.
Dependencies are inferred from the claim text.