PLL Supply Pre-Boost for Frequency Overshoot and Voltage Droop
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Solution Overview
Problem
Phase locked loops (PLLs) experience frequency overshoot when correcting phase or frequency changes, leading to increased supply voltage guard bands, which negatively impact system performance and limit the effectiveness of adaptive frequency scaling techniques.
Innovation Solution
An apparatus that temporarily boosts the supply voltage before a potential frequency overshoot event, allowing the PLL to lock quickly without long-term voltage guard bands, and reduces the voltage back to the expected level, thereby absorbing the overshoot impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the PLL is overdamped to mitigate frequency overshoot, then frequency stability is improved, but lock/relock time increases significantly
Solution Approach 1:
The patent applies preliminary action by detecting voltage droop conditions before they cause frequency overshoot and proactively adjusting the PLL parameters or supply voltage. The droop detector circuit monitors voltage conditions and triggers preventive measures (such as adjusting damping factors or voltage levels) before the frequency overshoot occurs, thus maintaining frequency stability without requiring excessive damping that would slow down lock/relock times.
2Stability of the object's composition
If supply voltage guard bands are increased to absorb frequency overshoot, then frequency stability is improved, but system performance decreases and minimum operating voltage increases
Solution Approach 1:
The patent detects voltage droop conditions in advance and triggers preventive voltage adjustments before frequency overshoot occurs. By proactively managing voltage levels based on detected droop conditions, the system maintains frequency stability without needing to permanently increase supply voltage guard bands, thus preserving system performance and keeping minimum operating voltage requirements low.
Solution Approach 2:
The system uses self-service by implementing an automatic droop detection and response mechanism that operates without external intervention. The droop detector circuit continuously monitors voltage conditions and automatically triggers corrective actions (such as adjusting PLL parameters or supply voltage) when droop is detected, enabling the system to self-correct frequency stability issues without impacting overall performance.
3Productivity
If adaptive frequency scaling is used to improve performance, then productivity is improved, but frequency overshoot occurs during transitions
Solution Approach 1:
The patent implements feedback by using a droop detector circuit that continuously monitors supply voltage conditions during AFS transitions. When voltage droop is detected, the system receives feedback and automatically adjusts PLL parameters or voltage levels to prevent frequency overshoot. This closed-loop feedback mechanism enables aggressive AFS transitions to improve performance while maintaining frequency stability through real-time corrections.
Data Source
AI summary
An apparatus and method are described, which prior to an event that could result in frequency overshoot, sends a signal to a voltage regulator or generator requesting a temporary supply voltage and/or current boost. This enables a clocking source, such as a phase locked loop (PLL) to lock fast while not needing any long-term voltage guard bands. The apparatus and scheme allows for on-the-fly change in supply voltage and/or clock frequency for a processor with little to no impact on Vmin During the clock frequency overshoot, the supply voltage is temporarily boosted and then reduced down to the expected voltage level of the power supply. Such boost allows for absorbing the clock frequency overshoot impact. The supply voltage level can be reduced in a step-wise fashion to avoid any potential undershoot in clock frequency.