CDR Charge Pump Circuit With Reduced Glitch Current
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing clock data recovery (CDR) systems face inadequacies due to high undesirable glitch currents caused by mismatched charge injection during phase switching, leading to static phase offset and significant parasitic capacitance, which affects device performance and jitter in high-data communication applications.
Innovation Solution
A charge pump circuit with a bias section and a switch section, including resistors directly coupled to a low-pass filter, is designed to generate controlled bias signals and reduce glitch currents by minimizing parasitic capacitance and noise, using PMOS and NMOS switches with resistors to manage charge injection effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional charge pump circuits are used in CDR systems, then charge injection can be achieved, but high glitch currents and parasitic capacitance cause static phase offset and performance degradation
Solution Approach 1:
A current recycling circuit is introduced as an intermediary component between the charge pump and the loop filter. This circuit acts as a mediator that captures and recycles the glitch current generated during phase detector switching, preventing it from directly injecting unwanted charge into the loop filter and causing static phase offset. The intermediary circuit thus isolates the harmful effect while preserving the useful charge injection function.
Solution Approach 2:
The patent converts the harmful glitch current into a beneficial resource by recycling it. The current recycling circuit captures the glitch current that would otherwise be wasted and causes harm, and redirects it to provide useful charge injection when needed. This transforms a harmful byproduct into a useful component of the charge pump operation, improving overall efficiency and reducing the need for additional charge injection current.
2Measurement precision
If charge pump current is increased to improve phase detection accuracy, then measurement precision improves, but glitch current and noise increase
Solution Approach 1:
The charge pump operation is segmented into distinct phases: useful charge injection phase and glitch current generation phase. The current recycling circuit separates these phases by capturing glitch current during switching transitions and storing it for later useful injection. This segmentation allows the system to maintain high charge injection current for accuracy while isolating the noise-generating glitch events, preventing them from degrading signal quality.
3Speed
If switching speed is increased to improve time response, then speed improves, but glitch current magnitude increases
Solution Approach 1:
The current recycling circuit performs preliminary action by pre-capturing and storing glitch current before it can cause harm. During phase detector switching, the recycling circuit is already in position to capture the glitch current immediately as it is generated, preventing it from directly affecting the loop filter. This preliminary capture action allows for fast switching without proportionally increasing the harmful effects of glitch current.
Data Source
AI summary
The present invention is directed to electrical circuits. According to an embodiment, the present invention provides a charge pump circuit with a bias section and a switch section. The switch section includes a first switch coupled to an early signal and a second switch coupled to a late signal. The charge pump additionally includes a low-pass filter. The switch section includes a first resistor and a second resistor. The first resistor is directly coupled to the first switch and the low-pass filter. The second resistor is directly coupled to the second switch and the first resistor. There are other embodiments as well.