PLL Charge Pump Current Bootstrapping for Stable Phase Margin
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Solution Overview
Problem
Existing phase locked loops (PLLs) face stability and phase margin issues due to variability in supply voltage, temperature, and process corners, which are exacerbated by the reliance on traditional reference current generators that consume significant power and occupy large die areas.
Innovation Solution
A charge pump circuit within a PLL generates a reference current using an auxiliary current and a bootstrap current, with a current mirror ensuring source and sink currents are substantially equal to the reference current, reducing the influence of supply voltage and temperature variations, and utilizing a source follower and diode-connected transistor to stabilize the reference current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a bandgap voltage reference circuit is used to generate reference current, then the reference current stability is improved, but power consumption increases and die area increases
Solution Approach 1:
The patent extracts the essential function of generating a stable reference current from the complex bandgap voltage reference circuit, implementing it through a simplified current mirror-based architecture that achieves comparable stability without the power and area overhead of traditional bandgap circuits
Solution Approach 2:
The patent uses current mirror circuits to copy and replicate reference current values across multiple branches, achieving stable current generation through geometric scaling of transistor dimensions rather than through complex voltage reference circuits
2Stability of the object's composition
If a bandgap voltage reference circuit is used to generate reference current, then the reference current stability is improved, but die area increases
Solution Approach 1:
The patent extracts the essential function of generating a stable reference current from the complex bandgap voltage reference circuit, implementing it through a simplified current mirror-based architecture that achieves comparable stability without the power and area overhead of traditional bandgap circuits
Solution Approach 2:
The patent achieves stable reference current generation by scaling transistor width-to-length ratios and using current mirror multiplication factors, replacing the need for large-area bandgap circuitry with compact transistor-based current control
3Use of energy by moving object
If traditional reference current generators are used, then power consumption and die area are reduced, but stability and phase margin deteriorate due to supply voltage and temperature variations
Solution Approach 1:
The patent implements feedback mechanisms through the charge pump loop that continuously adjusts the reference current based on phase error detection, compensating for supply voltage and temperature variations to maintain stability while keeping power consumption low
Solution Approach 2:
The patent uses dynamically adjustable current mirror ratios and transistor sizing that can be adapted to different operating conditions, allowing the reference current to self-adjust for temperature and supply voltage changes without requiring high power consumption
Data Source
AI summary
A phase locked loop with a charge pump circuit has increased stability and phase margin. The charge pump circuit feeds back its voltage output to generate a reference current. In one embodiment, the charge pump circuit comprises a current generator responsive to a charge voltage that has been output from the charge pump. The current generator generates a reference current based on the charge voltage and a supply voltage. The reference current may comprise a bootstrap current and an auxiliary current. The charge pump circuit also comprises a current mirror that generates a source current and a sink current that are substantially the same as the reference current. The charge pump circuit further comprises a charge voltage generator to generate the charge voltage based on the source current and the sink current. A related method is also disclosed. Other embodiments are provided, and each of the embodiments can be used alone or in combination with one another.