Ring VCO Level Shifting for 50% Duty Ratio Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing ring voltage controlled oscillators face challenges in maintaining a consistent duty ratio of output signals due to variations in transistor corners, which affect the speed and efficiency of the oscillator's operation.
Innovation Solution
The proposed solution involves a ring voltage controlled oscillator with an inverter chain circuit and a level shift circuit that includes P-channel and N-channel MOS transistors, coupled with a common mode voltage providing circuit to adjust the common mode voltage based on transistor corners, ensuring a duty ratio of 50% by adjusting the common mode voltage magnitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional ring VCO is used, then the oscillator can operate with simple structure, but the duty ratio of output signal varies due to transistor corner variations
Solution Approach 1:
A common mode voltage providing circuit is introduced as an intermediary component between the inverter chain and the output. This circuit dynamically adjusts the common mode voltage level based on transistor corner characteristics, thereby mediating the effect of process variations on the output signal duty ratio and maintaining consistent 50% duty ratio across different transistor corners.
Solution Approach 2:
The invention changes the common mode voltage parameter dynamically to compensate for transistor corner variations. By adjusting the common mode voltage level, the circuit counteracts the effects of process variations on transistor switching characteristics, ensuring that the output signal maintains a consistent duty ratio despite changes in transistor performance.
2Ease of manufacture
If transistor corners vary, then manufacturing cost may be reduced, but the speed and efficiency of the oscillator deteriorates
Solution Approach 1:
The common mode voltage providing circuit implements a feedback mechanism that senses the output signal characteristics and adjusts the common mode voltage accordingly. This feedback loop compensates for speed variations caused by transistor corner differences, ensuring that oscillators manufactured with varying transistor characteristics all achieve the target operating speed and efficiency.
3Device complexity
If no common mode voltage adjustment is applied, then the circuit complexity is low, but the output signal duty ratio consistency deteriorates
Solution Approach 1:
The common mode voltage providing circuit serves as an intermediary that stabilizes the duty ratio without requiring major structural changes to the oscillator core. By inserting this relatively simple voltage adjustment stage, the invention achieves stable 50% duty ratio output while maintaining the overall simplicity of the oscillator architecture.
Data Source
AI summary
A ring voltage controlled oscillator includes an inverter chain circuit including inverters disposed in stages, the inverters being coupled to each other in a chain form, and a level shift circuit configured to receive an output signal from the inverter chain circuit to output a level-shifted final output signal. The level shift circuit includes an output inverter including a PMOS transistor and an NMOS transistor, coupled in series between a power supply terminal and a ground voltage terminal, and a common mode voltage providing circuit configured to provide a common mode voltage to the output signal from the inverter chain circuit to generate an intermediate output signal, the common mode voltage being provided in different magnitudes depending on transistor corners of the NMOS transistor and the PMOS transistor. The output inverter receives and inverts the intermediate output signal to generate the level-shifted final output signal.