RLC Pulse Injection for Synchronizing Independent SoC Clocks
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Solution Overview
Problem
Multi-node systems with independent time bases face challenges in synchronizing their timing, as existing methods require direct adjustment of capacitors or other circuit components, which is not feasible in all configurations, especially in low-power applications like augmented reality eyewear devices.
Innovation Solution
An external passive RLC circuit is used to inject current pulses from a primary node's clock generator into a secondary node's clock generator, shifting its resonant frequency to synchronize with the primary node's output without altering capacitors, utilizing a ring oscillator and feedback circuit to maintain synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct adjustment of capacitors or circuit components is used to synchronize timing, then synchronization accuracy is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent introduces an external passive RLC circuit as an intermediary between the primary and secondary clock generator circuits. This RLC circuit receives current pulses from the primary node and injects them into the secondary node's clock generator, serving as a mediator that transfers timing information without requiring direct component adjustment between nodes. The RLC circuit's resonant frequency is pulled by the injected pulses to match the primary node's frequency, achieving synchronization through this intermediate element.
Solution Approach 2:
The patent replaces the mechanical/electrical adjustment of capacitors and circuit components with an electrical signal-based approach. Instead of physically adjusting capacitor values or circuit components to match frequencies, the system uses current pulse injection to electronically 'pull' the secondary crystal's resonant frequency to match the primary node. This substitution eliminates the need for manual component adjustment while maintaining synchronization accuracy.
2Measurement precision
If capacitor adjustment is performed to synchronize independent time bases, then timing synchronization is improved, but ease of operation deteriorates
Solution Approach 1:
The system enables self-service synchronization where the secondary node automatically adjusts its timing to match the primary node through the current pulse injection mechanism. The external passive RLC circuit and ring oscillator work together to automatically pull the secondary crystal's frequency to match the primary node's frequency without requiring manual intervention. The system self-regulates to maintain synchronization, eliminating the need for operators to adjust capacitors.
Solution Approach 2:
The external passive RLC circuit serves as an intermediary that simplifies the synchronization operation. Instead of requiring direct capacitor adjustment on the secondary node, the RLC circuit mediates the frequency matching process by receiving standardized current pulses from the primary node and translating them into appropriate frequency adjustments for the secondary node's crystal oscillator.
3Ease of operation
If current pulses are injected into clock generator circuit, then synchronization is achieved without capacitor adjustment, but device complexity increases
Solution Approach 1:
The patent extracts the synchronization complexity from the individual node circuits and places it in an external passive RLC circuit. By moving the frequency-matching functionality to an external component, the core clock generator circuits within each node remain simple and unchanged. The external RLC circuit handles all the complexity of frequency pulling and synchronization, allowing the internal node circuits to remain straightforward while achieving precise synchronization.
4Adaptability or versatility
If independent time bases are used in multi-node systems, then node independence is improved, but timing synchronization deteriorates
Solution Approach 1:
The system implements a feedback mechanism where current pulses from the primary node's clock generator are continuously injected into the secondary node's clock generator through the external passive RLC circuit. This creates a feedback loop that constantly corrects any frequency drift in the secondary node, pulling its resonant frequency to match the primary node. The feedback ensures that even though nodes operate with independent time bases, they remain synchronized through continuous frequency correction.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method effectively synchronizes the timing of nodes without requiring capacitor adjustments, ensuring accurate timestamping across nodes in low-power applications, such as augmented reality systems, by using current pulses to 'pull' the secondary node's crystal into synchronization with the primary node's frequency.
Implementation Method 1
shifting its resonant frequency to synchronize with the primary node's output
Implementation Method 2
inject current pulses generated from the clock generator circuit of a primary node into the clock generator circuit of a secondary node
Implementation Method 3
utilizing a ring oscillator and feedback circuit to maintain synchronization
Data Source
AI summary
A circuit includes a first system-on-chip (SoC) driven by a first clock generator and a second SoC driven by a second clock generator where the first clock generator and the second clock generator have independent time bases. The first and second clock generators are synchronized using an RLC circuit external to the first clock generator and the second clock generator that converts an output of the first clock generator into current pulses and injects the current pulses into the second clock generator to pull an output of the second clock generator into synchronization with the output of the first clock generator. The RLC circuit converts a voltage output of the first clock generator into current pulses at the resonant frequency or specific harmonics of the output of the first clock generator. The second clock generator may include a ring oscillator into which the current pulses are injected.