Laddered CMOS Ring Oscillator for Low-Power Multi-Phase Timing
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Solution Overview
Problem
Traditional ring oscillators face challenges in reducing time delay and increasing oscillation frequency while maintaining low power consumption, as adding inverters increases power consumption and propagation delay, affecting frequency operation.
Innovation Solution
A ring oscillator design incorporating a series of laddered inverter quantizer (LIQAF) circuits with a feedback loop, generating phase-shifted waveforms through multiple stages, allowing for increased output phases and lower power consumption by utilizing a chain of parallelized inverters with distinct propagation delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the number of inverters is increased to increase time delay, then the oscillation frequency decreases, but the power consumption increases
Solution Approach 1:
The patent segments the traditional single inverter delay element into multiple laddered inverter quantizer (LIQAF) stages. Each LIQAF stage provides a controlled time delay through its laddered structure, allowing the total delay to be adjusted by the number of stages rather than by simply adding more inverters in series. This segmentation enables finer control over delay while reducing the overall power consumption compared to using many traditional inverters.
Solution Approach 2:
The patent introduces dynamic control of the time delay through the laddered inverter quantizer structure, where the delay can be adjusted by changing the supply voltage or by selecting different tap points in the laddered structure. This dynamic adjustment capability allows the system to optimize the balance between delay and power consumption based on operational requirements, rather than being fixed by the number of inverters.
2Speed
If the supply voltage is increased to increase oscillation frequency, then the propagation delay decreases, but the power consumption increases
Solution Approach 1:
The patent employs dynamic voltage control of the LIQAF stages to adjust the oscillation frequency. By dynamically changing the supply voltage to the LIQAF circuits, the propagation delay through each stage can be adjusted, thereby controlling the oscillation frequency. This dynamic control allows frequency adjustment without the need to continuously operate at high voltages, thus reducing average power consumption compared to simply increasing the supply voltage.
3Measurement precision
If the number of LIQAF stages is increased to increase the number of output phases, then the phase resolution increases, but the device complexity increases
Solution Approach 1:
The patent designs the LIQAF circuit to serve multiple functions: it provides time delay, generates phase-shifted outputs, and enables frequency control through a single unified structure. Each LIQAF stage generates multiple phase-shifted waveforms simultaneously, so increasing the number of stages increases both the number of phases and the phase resolution without requiring separate circuits for each function. This multi-functionality reduces the overall device complexity compared to using separate circuits for delay, phase generation, and frequency control.
Data Source
AI summary
A ring oscillator includes a first set of at least three laddered inverter quantizer (LIQAF) circuits connected in stages that are in series, including a first LIQAF circuit and a last LIQAF circuit, and a feedback circuit from the last LIQAF circuit to the first LIQAF circuit having a logical NOT output compared to the first LIQAF circuit. A voltage input creates a pair of phase shifted waveforms in the first of the at least three LIQAF circuits that propagate sequentially through the stages of the at least three LIQAF circuits. Each stage has a pair of outputs to the next stage that are then phase shifted from the previous stage in the next stage.