Pre-Emphasis Driver Circuit With Low-Pass Filtering for Jitter Control
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Solution Overview
Problem
High-speed serial links face challenges in maintaining accurate data transmission due to signal losses and voltage jitter caused by pre-emphasis variations, leading to intersymbol interference and overstress conditions in driver switches.
Innovation Solution
The implementation of a method that generates a pre-emphasis signal as a phase-shifted and scaled version of the digital data signal, combined with low-pass filtering of current sources in a driver switch circuit to reduce voltage jitter, involves a transmitter circuit with multiple filters and current sources, and a driver switch circuit that adds the pre-emphasis signal to the digital data signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If pre-emphasis is applied to compensate for signal losses in high-speed data transmission, then signal amplitude and transition steepness are improved, but voltage jitter and intersymbol interference increase
Solution Approach 1:
The driver circuit is segmented into multiple independent current sources (first pull-up, second pull-up, first pull-down, second pull-down) that can be independently controlled. This segmentation allows selective application of pre-emphasis to specific signal components while isolating others, thereby reducing unwanted voltage jitter and intersymbol interference while maintaining signal integrity at high speeds.
Solution Approach 2:
Different current sources are assigned different functions with localized control: some current sources apply pre-emphasis to enhance signal amplitude and transition steepness, while others maintain stable operation to minimize voltage jitter. This local differentiation of current source characteristics resolves the contradiction between speed enhancement and signal integrity maintenance.
2Manufacturing precision
If pre-emphasis voltage is increased to maintain signal integrity, then transition steepness is improved, but driver switch overstress conditions occur
Solution Approach 1:
The driver circuit uses segmented current sources that can independently control pre-emphasis voltage levels. By dividing the driver function across multiple current sources, the circuit can apply high pre-emphasis voltage only where needed for transition steepness while keeping other portions at safe voltage levels, preventing driver switch overstress.
Solution Approach 2:
The circuit dynamically adjusts voltage parameters across different current sources based on operating conditions. By changing voltage levels locally rather than globally, the system achieves steep transitions when needed while preventing overstress conditions, resolving the contradiction between transition quality and component reliability.
3Power
If multiple current sources are used in the driver circuit to provide pre-emphasis, then signal amplitude is improved, but circuit complexity increases
Solution Approach 1:
The driver circuit is divided into segmented current sources that can be independently controlled. This segmentation provides fine-grained control over signal amplitude while maintaining a relatively simple overall architecture. Each current source handles a specific function, making the circuit manageable despite having multiple components.
Solution Approach 2:
Multiple current sources are designed with universal control mechanisms that allow them to perform different functions (pre-emphasis, signal boosting, jitter reduction) based on configuration. This multi-functionality reduces the need for entirely separate circuits, thereby limiting the increase in overall circuit complexity while still achieving high signal amplitude.
Data Source
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AI summary
One embodiment relates to a method of driving a transmission signal with pre-emphasis having minimal voltage jitter. A digital data signal is received, and a pre-emphasis signal is generated. The pre-emphasis signal may be a phase shifted and scaled version of the digital data signal. An output signal is generated by adding the pre-emphasis signal to the digital data signal within a driver switch circuit while low-pass filtering is applied to current sources of the driver switch circuit. Other embodiments, aspects, and features are also disclosed.