Ring Oscillator Clock Control for Fast Low-Power Convergence
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Solution Overview
Problem
Existing clock generators face challenges in implementing a control loop that rapidly converges to a frequency and voltage state with low electrical consumption, especially under PVT variations.
Innovation Solution
A clock generator comprising a ring oscillator, a frequency detector, and a control circuit that adjusts the loop delay parameter and supply voltage based on feedback signals to regulate the output frequency, ensuring convergence to a low-power state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a control loop is implemented to regulate clock frequency for low-power operation, then power consumption is reduced, but the convergence speed to the target frequency state becomes slow
Solution Approach 1:
The control loop is pre-configured with optimal parameters and the frequency detector is pre-calibrated to enable rapid convergence. The system prepares the control mechanism in advance with appropriate gain values and integration constants that allow quick response to frequency deviations while maintaining low steady-state power consumption.
Solution Approach 2:
The control loop parameters are made dynamic rather than static. The controller adjusts its response characteristics based on the operating state - using higher gain during transient convergence phases to reduce settling time, and lower gain during steady-state operation to minimize power consumption. This dynamic adaptation resolves the contradiction between fast convergence and low power operation.
2Loss of energy
If the supply voltage is reduced to lower power consumption, then energy efficiency improves, but the frequency stability under PVT variations deteriorates
Solution Approach 1:
A feedback mechanism continuously monitors the actual clock frequency and compares it with the target frequency. The frequency detector generates error signals that are fed back to the control loop, which then adjusts the ring oscillator parameters to compensate for frequency deviations caused by low supply voltage and PVT variations, thereby maintaining frequency stability while operating at reduced power consumption.
Solution Approach 2:
The system dynamically changes multiple parameters including supply voltage, loop delay, and oscillator bias currents to maintain optimal frequency stability at low power. By coordinating adjustments of these parameters rather than relying on a single parameter, the system achieves frequency regulation even at reduced supply voltages where traditional single-parameter control would fail.
3Speed
If the loop delay parameter is minimized to increase frequency, then the output frequency increases, but the phase margin and oscillation stability are compromised
Solution Approach 1:
The loop delay parameter is made dynamically adjustable rather than fixed. The control loop continuously optimizes the delay parameter based on real-time feedback about oscillation stability and frequency requirements. This allows the system to use minimal delay for maximum frequency when stable, while automatically increasing delay when stability margins are compromised, thus dynamically resolving the trade-off between frequency and stability.
Solution Approach 2:
Multiple related parameters are changed in coordination - not just the loop delay but also the oscillator stage delays, buffer characteristics, and loading conditions. This multi-parameter optimization allows the system to push the loop delay to its stability limit while maintaining oscillation stability through compensating changes in other parameters, thereby achieving maximum frequency without sacrificing reliability.
Data Source
AI summary
The present disclosure relates to a clock generator comprising: a ring oscillator configured to generate an output frequency signal; a frequency detector configured to compare a frequency of the output frequency signal with r times a frequency of a reference frequency signal and to generate a feedback signal; and a control circuit configured to: control a loop delay parameter of the ring oscillator and a supply voltage of the ring oscillator based on the feedback signal; reduce the frequency of the output frequency signal when its frequency is higher than r times the frequency of the reference frequency signal by reducing the supply voltage; and increase the frequency of the output frequency signal when its frequency is lower than r times the frequency of the reference frequency signal by reducing the loop delay parameter.