Injection-Locked Oscillator Circuit With Expanded PVT Lock Range
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Solution Overview
Problem
Injection-locked oscillators have a limited lock range, making them unstable under PVT variations, as the free-running frequency of on-chip oscillators often deviates from the reference signal frequency, leading to reduced stability and inability to maintain lock.
Innovation Solution
A circuit and method utilizing multiple injection-locked oscillators with a lock detector, alignment monitor, self-samplers, and a clock selector to determine and select a locked oscillator, expanding the lock range by sampling outputs and adjusting based on pulse reference signals, without increasing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single injection-locked oscillator is used to generate frequency signals, then the circuit structure is simple, but the lock range is narrow and cannot cover PVT-induced frequency variations
Solution Approach 1:
The patent divides a single oscillator system into multiple parallel injection-locked oscillators (N≥2), each with different free-running frequencies. This segmentation allows the system to cover a broader frequency range through PVT variations, as each oscillator responds differently to process, voltage, and temperature changes, thereby expanding the overall lock range while maintaining individual oscillator simplicity
Solution Approach 2:
The patent combines multiple injection-locked oscillators into a unified system with a shared reference signal input and a common selection mechanism. By merging the outputs of N oscillators through an OR gate and selection circuitry, the system achieves an expanded lock range that covers the frequency variations caused by PVT, while the combined structure provides redundancy and improved reliability
2Adaptability or versatility
If multiple injection-locked oscillators with different free-running frequencies are used, then the lock range is expanded, but the device complexity increases
Solution Approach 1:
The patent implements dynamic selection among multiple oscillators based on their locking status. The selection circuitry dynamically switches between different oscillators depending on which ones are successfully locked to the reference signal, allowing the system to adapt to PVT variations in real-time. This dynamic approach enables the system to maintain functionality across a wide frequency range without requiring all oscillators to operate simultaneously at full power
Solution Approach 2:
The system employs self-diagnosis and self-selection mechanisms where the oscillators automatically indicate their locking status through their output signals. The selection circuitry automatically identifies and selects a locked oscillator without external intervention, enabling the system to self-adjust to PVT variations. This self-service capability reduces the need for complex external control mechanisms while maintaining expanded lock range
3Adaptability or versatility
If a wide lock range is achieved through multiple oscillators, then PVT variations are covered, but power consumption increases
Solution Approach 1:
The patent activates multiple oscillators in parallel but only selects one locked oscillator for final output. By using partial action (activating N oscillators but selecting only 1 for output), the system achieves expanded lock range coverage while limiting power consumption to essentially one fully-active oscillator plus the overhead of N oscillators operating at reduced power levels. The OR gate logic ensures that power is not wasted on multiple simultaneous full-power outputs
Solution Approach 2:
The system continuously monitors the locking status of multiple oscillators and discards (deactivates or ignores) those that are not locked. When PVT variations cause frequency drift, the system recovers by switching to a different oscillator that remains locked. This discard-and-recover mechanism allows the system to maintain expanded lock range capability while minimizing power consumption by actively using only the necessary oscillator at any given time
Data Source
AI summary
The present disclosure provides a circuit and method for expanding the lock range of injection-locked oscillators. The circuit includes N injection-locked oscillators and a lock detector, where the lock detector includes an alignment monitor, a clock selector, and N self-samplers. A pulse reference signal is inputted into the N injection-locked oscillators, and the output of each injection-locked oscillator is connected to the clock selector and the corresponding self-sampler. The self-samplers sample the outputs of the N injection-locked oscillators and output the sampling results to the alignment monitor. The alignment monitor monitors the sampling results, determines the locking conditions of the injection-locked oscillators, and turns off the unlocked oscillators. The clock selector selects a locked oscillator and transmits the output of the locked oscillator as a system lock.