PLL Circuit Layout for Gate Leakage and Jitter Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Phase-locked loop circuits face issues with unintended voltage fluctuations due to gate leak currents, leading to jitter and reduced timing margins, particularly in high-voltage transistors which have larger variations in threshold voltage, limiting the frequency range for oscillation.
Innovation Solution
The design incorporates a low-voltage transistor with a thinner gate oxide film for the voltage controlled oscillator and a high-voltage transistor with a thicker gate oxide film for the low-pass filter, along with a buffer circuit to suppress gate leak currents and maintain stable voltage levels, ensuring a wider frequency range for oscillation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a high-voltage transistor with thicker gate oxide film is used in the voltage controlled oscillator, then breakdown voltage is improved, but gate leak current increases causing voltage fluctuations and jitter
Solution Approach 1:
The patent applies different gate oxide film thicknesses to different transistors based on their specific functional requirements. The voltage controlled oscillator uses a low-voltage transistor with thinner gate oxide film to minimize leak current and voltage fluctuations, while the low-pass filter uses a high-voltage transistor with thicker gate oxide film to withstand higher voltages. This localized optimization resolves the contradiction by matching transistor characteristics to specific circuit needs rather than using a uniform design throughout.
2Reliability
If a low-voltage transistor with thinner gate oxide film is used in the voltage controlled oscillator, then gate leak current is reduced improving voltage stability, but breakdown voltage decreases
Solution Approach 1:
The patent implements local quality by assigning different transistor types to different circuit blocks. The voltage controlled oscillator, which requires high voltage stability and low jitter, uses a low-voltage transistor with thinner gate oxide film. The low-pass filter, which tolerates voltage variations better, uses a high-voltage transistor with thicker gate oxide film. This spatial differentiation of transistor characteristics resolves the contradiction between voltage stability and breakdown voltage.
3Ease of manufacture
If transistors with uniform gate oxide film thickness are used, then manufacturing complexity is reduced, but threshold voltage variations cause jitter and limit frequency range
Solution Approach 1:
The patent applies local quality by specifying different gate oxide film thicknesses for transistors in different circuit locations based on their functional requirements. The voltage controlled oscillator uses transistors with thinner gate oxide films for lower threshold voltage and reduced jitter, while the low-pass filter uses transistors with thicker gate oxide films. This differentiated approach improves threshold voltage control precision for critical oscillation while maintaining manufacturing feasibility through standardized process variations.
Data Source
AI summary
The phase-locked loop circuit according to one embodiment includes a low-pass filter including a first transistor, and a second transistor. The low-pass filter converts a first current into a first voltage, and a second current into a second voltage. The first current and the second current are generated in accordance with a pulse width of the same signal. The first transistor includes a gate input with the first voltage, a first terminal grounded, a second terminal electrically coupled to a gate of the second transistor, and a gate oxide film thicker than that of the second transistor. The second transistor includes the gate input with the second voltage.