Cascoded Charge Pump Fast Turn On Off Speed
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Solution Overview
Problem
Conventional charge pumps in phase locked loops exhibit slow turn-on and turn-off response times, leading to noise introduction due to the ripple effect caused by the sequential activation of cascoded switches, which affects the alignment of reference and divided frequency phases.
Innovation Solution
The integration of additional switches and capacitors in the charge pump circuit allows for simultaneous turn-on and turn-off of cascoded switches, reducing ripple delay and improving response times by directly coupling slower nodes with control signals and voltage sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If cascoded switches are used in the charge pump to maintain constant current, then current stability is improved, but turn-on and turn-off response times become slow
Solution Approach 1:
The patent applies preliminary action by pre-charging capacitor C1 through switch P10 before the main switching operation. When switch P5 needs to turn on, the capacitor C1 is already charged and can immediately supply current, eliminating the delay that would otherwise occur while the cascoded switches sequentially activate. This pre-positioning of energy resolves the contradiction by maintaining current stability through the capacitor while achieving fast response times through immediate discharge capability.
2Ease of operation
If sequential activation of cascoded switches is used, then current control is simplified, but ripple delay increases causing noise
Solution Approach 1:
The patent introduces capacitor C1 as an intermediary element between the control switches and the current output. This capacitor absorbs the ripple effects generated by sequential switch activation and smooths the current delivery. The intermediary capacitor maintains the simplicity of cascoded switch control while eliminating the harmful noise and ripple that would otherwise be generated by the sequential activation mechanism.
3Speed
If additional switches and capacitors are added to reduce response time, then response speed is improved, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the charge pump circuit into distinct functional modules: the cascoded switch row for current control, the capacitor C1 for speed enhancement, and switch P10 for capacitor charging. This modular segmentation allows each component to perform its specific function efficiently, achieving fast response times without creating an undifferentiated complex circuit. The segmented architecture makes the additional components manageable and purpose-driven rather than arbitrarily complex.
Data Source
AI summary
A charge pump includes a first switch coupled between a first voltage source and a first node, second switch coupled between the first node and a second node, a third switch coupled between the second node and a third node, the third node is for outputting from the charge pump. A fourth switch is coupled between the output node and a fourth node, a fifth switch is coupled between the fourth node and a fifth node, and a sixth switch is coupled between the fifth node and ground. A seventh switch is coupled between ground and the first node and an eighth switch is coupled between a second voltage source and the fifth node. A first capacitor is coupled between the second node and a first voltage signal and a second capacitor is coupled between the fourth node and a second voltage signal.