Single-PLL VCO Load Switching for Wide HDMI Frequency Lock
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Solution Overview
Problem
Existing High Definition Multimedia Interface (HDMI) receivers require multiple phase-locked loops (PLLs) to cover a wide frequency range, leading to increased silicon area consumption, power consumption, and complexity due to the limited tuning range of each PLL.
Innovation Solution
A single PLL with an analog comparator circuit and digital control circuit that automatically adjusts the tunable load of the voltage-controlled oscillator (VCO) to cover a wider frequency range by switching between multiple load circuits based on the output of the charge pump voltage, allowing for smooth operation over the HDMI frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple PLLs are used to cover the wide frequency range, then the frequency coverage is improved, but the silicon area consumption increases
Solution Approach 1:
The frequency range is divided into multiple bands, and a single PLL is used with the ability to switch between different frequency bands. The segmentation is applied to the frequency spectrum rather than physically dividing the PLL circuit into multiple units, thus maintaining frequency coverage while reducing silicon area.
Solution Approach 2:
A single PLL circuit is designed to perform multiple frequency coverage functions by incorporating band selection capability. The same PLL hardware can operate across different frequency ranges (e.g., 25-85 MHz and 85-165 MHz) by switching its operating mode, making it universal rather than dedicated to a single frequency band.
2Adaptability or versatility
If multiple PLLs are used to cover the wide frequency range, then the frequency coverage is improved, but the power consumption increases
Solution Approach 1:
The frequency spectrum is segmented into multiple bands, and the PLL is configured to activate only the necessary frequency band for the current operating conditions. This selective activation reduces power consumption compared to having multiple PLLs continuously operational or switching between them.
Solution Approach 2:
The system automatically selects the appropriate frequency band based on the input signal characteristics without requiring external control. The PLL self-adjusts its operating band to match the required frequency range, eliminating the need for multiple independently controlled PLLs and reducing overall power consumption.
3Adaptability or versatility
If multiple PLLs are used to cover the wide frequency range, then the frequency coverage is improved, but the device complexity increases
Solution Approach 1:
The frequency range is segmented into multiple operational bands within a single PLL architecture. Instead of using multiple complete PLL circuits, the invention segments the frequency coverage capability within one PLL by switching its operating parameters, thereby reducing device complexity while maintaining comprehensive frequency coverage.
Solution Approach 2:
A single PLL is designed with multi-functional capability to cover multiple frequency bands (25-85 MHz and 85-165 MHz). The PLL incorporates band selection logic and can be configured for different operating ranges, making one circuit perform the work of multiple dedicated circuits and simplifying the overall device architecture.
Data Source
AI summary
The present invention provides a method and mechanism for adapting a single phase-locked loop (PLL) for a wider range of frequencies than has been possible with prior art solutions. An analog comparator circuit that senses the output of a charge pump and provides a signal to a digital control circuit to choose a suitable load circuit for the PLL voltage controlled oscillator (VCO). The analog comparator with the digital control circuit changes the VCO loads to select the best VCO range to achieve the incoming signal frequency lock. A single PLL with the VCO load selection method disclosed, with use of built-in hysteresis, in addition to the phase and frequency feedback of the prior art, allows multiple overlapping frequency ranges to be covered in a stable fashion. This enables frequency locking of the PLL over a wide range of frequencies with a small die size and low power consumption.