Dual Charge Pump PLL Filtering for Low-Noise Jitter Suppression
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Solution Overview
Problem
Classic PLL circuits face challenges in suppressing long-term jitter without increasing circuit scale, as they struggle to manage noise from resistance elements while maintaining capacitance values within specifications.
Innovation Solution
The PLL circuit design includes a phase comparator, first and second charge pumps, a filter that removes high-frequency components, an integrator for current integration, and a voltage-current conversion circuit, allowing for independent adjustment of capacitance and resistance values without mutual influence, thereby reducing noise and jitter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the capacitance value of the capacitative element Cint is increased to suppress long-term jitter, then the long-term jitter is reduced, but the circuit scale increases
Solution Approach 1:
The patent divides the single charge pump into two separate charge pumps (first charge pump and second charge pump), each handling different frequency components. The first charge pump handles low-frequency components while the second charge pump handles high-frequency components, allowing independent optimization without increasing overall circuit scale
Solution Approach 2:
The patent introduces a frequency dimension by separating the charge pump functionality into two distinct frequency domains. By using two charge pumps with different operating characteristics, the system can suppress long-term jitter through proper frequency-domain separation without requiring larger capacitance values
2Object-generated harmful factors
If the resistance value of the resistance element Rpr is decreased to reduce noise, then the noise is reduced, but the long-term jitter suppression capability deteriorates
Solution Approach 1:
The patent segments the noise and jitter suppression functions into two separate charge pumps. The first charge pump is optimized for low-frequency jitter suppression with higher resistance tolerance, while the second charge pump handles high-frequency noise with lower resistance requirements, allowing both objectives to be achieved simultaneously
Solution Approach 2:
Different charge pumps are designed with different local characteristics optimized for their specific frequency domains. The first charge pump has parameters optimized for low-frequency operation while the second charge pump has parameters optimized for high-frequency operation, allowing each to perform its specific function effectively
3Stability of the object's composition
If the capacitance value of the capacitative element Cint is increased to maintain zero point frequency, then the zero point frequency is maintained, but the circuit scale increases
Solution Approach 1:
The patent segments the frequency stabilization function across two charge pumps with different capacitance values. The first charge pump uses a larger capacitance for low-frequency stability while the second charge pump uses a smaller capacitance for high-frequency response, maintaining overall zero point frequency stability without requiring a single large capacitance value
Solution Approach 2:
The system dynamically handles different frequency components through two separate charge pumps, allowing the zero point frequency to be maintained through coordinated operation rather than relying on a single large capacitance value, thus avoiding circuit scale increase
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
This configuration effectively suppresses output noise and long-term jitter within specified ranges without increasing the circuit scale, improving stability and performance.
Implementation Method 1
a filter that outputs a first current obtained by removing a high frequency component of the output current of the first charge pump
Implementation Method 2
an integrator that integrates the output current of the second charge pump and outputs an integrated result
Implementation Method 3
a voltage-current conversion circuit that outputs a second current according to an integrated result of the integrator
Data Source
AI summary
A PLL circuit includes: a phase comparator for detecting a phase difference between a reference signal and a feedback signal; a first charge pump for outputting a current Ipr according to a detection result of the phase comparator; a second charge pump for outputting a current Iint according to the detection result of the phase comparator; a filter for outputting a current Iprop from which a high frequency component of the Ipr is removed; an integrator for integrating the Iint; a voltage-current conversion circuit for outputting a current Ivi according to an integrated result of the integrator; and an oscillator that generates an oscillating signal of a frequency according to a current Iro, a sum of the Iprop and the Ivi, and feeds it back to the phase comparator.