SYSREF Clock Interpolator for Precise Rising Edge Alignment
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Solution Overview
Problem
Electronic devices with varying device clock frequencies require precise timing synchronization, as the timing windows for synchronization signals like SYSREF clocks differ significantly across systems, posing challenges in maintaining synchronization across components.
Innovation Solution
A SYSREF generation circuit comprising a frequency divider, an interpolator, and a latch, which generates a SYSREF clock signal by dividing the device clock signal and providing granular delay steps to position the rising edge of the SYSREF clock within a valid assertion window, ensuring compliance with standards like JESD204B, using an analog phase interpolator with digital-to-analog converters for precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a frequency divider is used to generate SYSREF clock from device clock, then the SYSREF clock frequency can be reduced to meet timing requirements, but the timing precision and adjustability are insufficient to position the rising edge within a narrow valid assertion window
Solution Approach 1:
The frequency divider is segmented into multiple stages (first frequency divider and second frequency divider) with different division ratios. The first frequency divider provides coarse frequency reduction while the second frequency divider provides fine-tuned frequency adjustment. This segmentation allows precise control of the SYSREF clock frequency and rising edge position within the valid assertion window, resolving the contradiction between timing precision and circuit complexity by breaking down a single complex divider into manageable stages.
Solution Approach 2:
The patent introduces dynamic adjustability to the frequency divider system through selectable division ratios and programmable control. The division ratios can be dynamically configured to match different device clock frequencies and timing requirements. This dynamic capability enables the system to adapt to varying timing windows and clock frequencies, achieving high timing precision without requiring an overly complex fixed-architecture circuit.
2Adaptability or versatility
If the SYSREF clock timing is adjusted to meet different device clock frequencies, then interoperability across components is improved, but the timing window constraints become more difficult to satisfy
Solution Approach 1:
The patent employs parameter changes by allowing the division ratios of the frequency dividers to be programmatically adjusted. This enables the SYSREF clock frequency and phase to be tuned to match different device clock frequencies while maintaining compliance with timing window requirements. The ability to change parameters (division ratios) dynamically allows the system to adapt to various interoperability scenarios without sacrificing timing precision.
Solution Approach 2:
The frequency divider circuit is designed with universal applicability through programmable division ratios that can accommodate different device clock frequencies and timing requirements. The same circuit architecture can serve multiple functions: generating SYSREF clock for different clock rates, adjusting timing offsets, and meeting various timing window constraints. This multi-functionality enhances interoperability across different components while maintaining manufacturing precision through a unified configurable approach.
3Measurement precision
If granular delay steps are introduced to position the rising edge of SYSREF clock, then timing accuracy within the valid assertion window is enhanced, but the circuit complexity and control requirements increase
Solution Approach 1:
The delay adjustment mechanism is segmented into discrete granular steps through the multi-stage frequency divider architecture. Each divider stage contributes to the overall delay adjustment in controlled increments. This segmentation provides granular control over the rising edge position without requiring a single complex continuous delay element, thereby enhancing positioning accuracy while keeping the control circuitry manageable through modular stages.
Solution Approach 2:
The patent implements partial action by providing just enough delay granularity needed to position the rising edge within the valid assertion window, rather than offering excessive continuous adjustment capability. The discrete delay steps are sufficient to meet timing requirements without over-engineering the control circuitry. This approach achieves the necessary rising edge positioning accuracy while avoiding unnecessary complexity in the control logic.
Data Source
AI summary
In some embodiments, an apparatus comprises a device clock configured to generate a device clock signal a synchronization (SYSREF) clock generation circuit configured to receive the device clock signal from the device clock. The SYSREF clock generating circuit comprises a SYSREF divider configured to generate a SYSREF clock at least partially according to the device clock signal, an interpolator configured to generate a shifted clock at least partially according to the device clock signal, and a latch coupled to the SYSREF divider and the interpolator and configured to sample the SYSREF clock at a rising edge of the shifted clock.