Charge-Sharing DCO Locking for Low-Error PLL Frequency Generation
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Solution Overview
Problem
Phase locked loops (PLLs) in circuits face challenges in generating high-frequency signals with reduced phase and frequency errors, particularly in applications requiring precise phase tracking and temperature compensation.
Innovation Solution
A ring based digitally controlled oscillator (DCO) is coupled with a charge-sharing circuit, incorporating charge-sharing capacitors, switches, and digital-to-analog converters (DACs), which adjusts the closed loop transfer function to reduce phase errors by sharing charge during specific time intervals, aligning oscillating signal phases with ideal waveforms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a phase locked loop is used to generate high-frequency signals, then the output signal frequency can be multiplied from a reference signal, but phase errors and frequency errors increase
Solution Approach 1:
The patent implements a feedback mechanism where the oscillating signal from the DCO is compared against an ideal waveform to detect phase errors. A charge-sharing circuit then applies corrective voltage adjustments based on these detected errors, continuously refining the output signal to reduce phase and frequency deviations while maintaining high-frequency operation
Solution Approach 2:
The patent replaces traditional analog phase-adjustment mechanisms with a digitally controlled oscillator that uses digital-to-analog converters and charge-sharing circuits. This substitution allows for more precise electronic control of phase and frequency by sharing charge between capacitors under digital control, achieving better precision at high frequencies
2Measurement precision
If charge-sharing capacitors and switches are added to the DCO circuit, then phase errors are reduced, but device complexity increases
Solution Approach 1:
The patent merges the charge-sharing circuit functionality directly into the DCO structure by integrating capacitors and switches with the existing oscillator circuitry. The DACs and charge-sharing elements are combined with the DCO cores, allowing phase correction to be achieved through integrated circuit operations rather than separate external components, thus managing complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The charge-sharing mechanism effectively reduces phase and frequency errors in the output oscillating signal, enhancing the precision and stability of high-frequency signal generation in PLLs.
Implementation Method 1
the charge on the connection node capacitor is shared with the charge on the charge-sharing capacitor at each charge-sharing time interval
Data Source
AI summary
An integrated circuit device includes a digitally controlled oscillator (DCO), two charge-sharing capacitors, two charge-sharing switches, two pre-charge switches, and two DACs. The DCO has a first inverter and a second inverter. A first charge-sharing capacitor has a first terminal coupled to an input terminal of the first inverter through a first charge-sharing switch. A first DAC has an output terminal coupled to the first terminal of the first charge-sharing capacitor through a first pre-charge switch. A second charge-sharing capacitor has a first terminal coupled to an input terminal or an output terminal of the second inverter through a second charge-sharing switch. A second DAC has an output terminal coupled to the first terminal of the second charge-sharing capacitor through a second pre-charge switch.