PLL Charge Pump Reference Current Bootstrapping
Find Innovative SolutionsGenerate Solutions
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 not effectively addressed by current reference current generators that often consume significant power and require 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 the same as the reference current, reducing the influence of supply voltage and temperature variations, and providing improved stability and phase margin without significant power consumption or die area increase.
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 only requires basic current sources and mirrors, thereby eliminating the need for complex voltage reference circuits while maintaining current stability
Solution Approach 2:
The patent uses current mirror circuits to copy and replicate reference current across multiple branches, ensuring stability through precise current replication rather than through complex voltage regulation, which reduces both power consumption and circuit complexity
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 removes the unnecessary bandgap voltage reference circuitry and retains only the essential current mirror and current source components needed to generate stable reference current, significantly reducing the die area occupied by the reference current generator
Solution Approach 2:
The patent employs compact current mirror implementations that achieve precise current copying with minimal transistor sizes, reducing the overall die area while maintaining the stability required for accurate reference current generation
3Device complexity
If existing reference current generators are used, then the circuit complexity is reduced, but the influence of supply voltage and temperature variations increases
Solution Approach 1:
The patent implements automatic bootstrapping where the charge pump output voltage is fed back to adjust the reference current, creating a negative feedback loop that compensates for supply voltage and temperature variations without requiring complex external regulation circuits
Solution Approach 2:
The reference current generator uses itself to compensate for its own variations through the bootstrapping mechanism, where the charge pump output automatically adjusts the reference current to maintain stability despite environmental changes, eliminating the need for separate compensation circuits
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.