DisplayPort CDR Multi-Band Oscillator With Automatic Band Selection
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Solution Overview
Problem
Existing DisplayPort clock data recovery (CDR) circuits struggle to support a wide range of data rates from 1.62 Gb/s to 20 Gb/s, often using manual band selection and single-band oscillators that fail to maintain noise and jitter characteristics, and multi-band oscillators lack automatic band setting capabilities.
Innovation Solution
A method and apparatus for automatic band selection using a wideband clock and data recovery circuit with a multi-band oscillator, employing a bang-bang phase detector, logic gates, a latch, and an up-down counter to automatically adjust bands based on data rate detection, ensuring fast frequency tracking and stable clock generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single-band oscillator is used to support a wide range of frequencies, then the frequency range is expanded, but noise and jitter characteristics deteriorate due to great gain requirements
Solution Approach 1:
The oscillator is divided into multiple bands (first band and second band) with different frequency ranges. The first band covers lower frequencies while the second band covers higher frequencies, allowing each band to operate with optimized gain characteristics that maintain low noise and jitter, while collectively supporting a wide frequency range from 1.62 Gb/s to 20 Gb/s
Solution Approach 2:
The system dynamically switches between different oscillator bands based on the detected data rate. The automatic band selection circuit monitors the incoming signal frequency and automatically selects the appropriate band, enabling the oscillator to adapt its operating characteristics to match the required frequency while maintaining optimal noise and jitter performance
2Reliability
If a multi-band oscillator is used to maintain noise and jitter characteristics, then noise and jitter performance is improved, but automatic band setting capability is lost requiring manual selection
Solution Approach 1:
The system incorporates an automatic band selection circuit that autonomously monitors the incoming signal characteristics and automatically selects the appropriate oscillator band without requiring manual intervention. The circuit detects the data rate and automatically configures the oscillator to the correct band, making the system self-configuring and eliminating the need for external manual band selection
Solution Approach 2:
The automatic band selection circuit continuously monitors the incoming signal frequency and provides feedback to the oscillator control logic. Based on this feedback, the system automatically adjusts the oscillator band selection to match the detected data rate, creating a closed-loop system that maintains optimal performance across varying frequency conditions
3Adaptability or versatility
If existing CDR circuits are used for DisplayPort, then they can operate in single-band mode, but they fail to support data rates up to 20 Gb/s
Solution Approach 1:
The oscillator system is designed to perform multiple functions by incorporating both first and second bands within a single integrated structure. The same oscillator circuit can operate in different band configurations to support various data rates from 1.62 Gb/s to 20 Gb/s, making the CDR circuit universally applicable across different DisplayPort versions and data rate requirements without requiring separate hardware designs
Data Source
AI summary
Provided are a method and an apparatus for automatic band selection for DisplayPort. The method may include: performing an operation on output signals of a bang-bang phase detector (BBPFD) by respective logic gates and outputting the output signal on which the operation has been performed; generating CUP, CDN, and HOLD signals according to a predefined condition by inputting the output signal to a latch; increasing or decreasing a bit count by inputting the generated CUP, CDN and HOLD signals to an up-down counter; and adjusting a band in correspondence with the increase or decrease in the bit count.