Adjustable Vref Generator for Single-Ended Channels
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Solution Overview
Problem
Existing reference voltage generators for single-ended communication channels lack the flexibility to optimize the reference voltage (Vref) for both non-degraded and degraded conditions, particularly due to their inability to independently vary the Vref-to-Vddq slope and offset, which affects voltage and timing margins in the presence of noise and distortion.
Innovation Solution
An improved Vref generator that includes an adjustable-resistance voltage divider and a current source, allowing independent adjustment of the Vref slope and offset, enabling optimization of the Vref voltage at different Vddq values by varying the resistances and injected current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a simple resistor-based voltage divider is used for Vref generation, then the device complexity is reduced and ease of manufacture is improved, but the adaptability to optimize Vref for both non-degraded and degraded channel conditions deteriorates
Solution Approach 1:
The patent implements dynamic adjustability in the Vref generator by introducing programmable current sources that can be controlled to provide different current levels. This allows the voltage divider output to be dynamically adjusted based on channel conditions (non-degraded or degraded), enabling the system to adapt its reference voltage characteristics without changing the physical resistor network structure.
Solution Approach 2:
The patent changes the electrical parameters of the Vref generator by introducing programmable current sources that can vary the current injection level into the voltage divider. This allows the Vref voltage level and its relationship to Vddq to be adjusted as a variable parameter rather than a fixed value, enabling optimization for different channel degradation scenarios.
2Reliability
If the Vref generator is designed to optimize voltage margins, then the reliability of data sensing is improved, but the flexibility to adjust Vref for different Vddq conditions deteriorates
Solution Approach 1:
The patent makes the Vref generator dynamic by implementing programmable current sources that can be controlled based on operating conditions. This allows the system to maintain optimized voltage margins through active control rather than fixed design, enabling the same circuit to adapt to different Vddq conditions while preserving reliability.
Solution Approach 2:
The patent employs feedback mechanisms where the system can detect channel conditions and Vddq levels, then adjust the current injection into the voltage divider accordingly. This closed-loop approach ensures that voltage margins are maintained optimally across varying conditions, combining reliability with adaptability.
3Device complexity
If the Vref generator uses a fixed voltage divider ratio, then the device complexity is reduced, but the ability to independently vary Vref slope and offset deteriorates
Solution Approach 1:
The patent introduces dynamic control elements (programmable current sources) into the voltage divider structure. These components allow the division ratio and offset to be adjusted programmatically without requiring multiple physical resistor networks, achieving variable slope and offset control with minimal additional complexity.
Solution Approach 2:
The patent makes the voltage divider circuit multi-functional by adding programmable current injection capability. The same basic voltage divider structure can serve multiple functions: fixed ratio division, variable ratio division, and offset adjustment, all controlled through programming the current sources rather than requiring separate hardware for each function.
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 solution enhances the flexibility of Vref generation, allowing for optimal voltage and timing margins in both non-degraded and degraded communication channel conditions, improving data sensing reliability by centering the reference voltage near the centroid of the data eye, even under varying Vddq conditions.
Implementation Method 1
The voltage divider comprises adjustable resistances Ra and Rb forming a voltage divider between I/O power supplies Vddq and Vssq, with Vref generated at an intervening node
Data Source
AI summary
An improved reference voltage (Vref) generator useable, for example, in sensing data on single-ended channels is disclosed. The Vref generator can be placed on the integrated circuit containing the receivers, or may be placed off chip. In one embodiment, the Vref generator comprises an adjustable-resistance voltage divider in combination with a current source. The voltage divider is referenced to I/O power supplies Vddq and Vssq, with Vref being generated at a node intervening between the adjustable resistances of the voltage divider. The current source injects a current into the Vref node and into a non-varying Thevenin equivalent resistance formed of the same resistors used in the voltage divider. So constructed, the voltage generated equals the sum of two terms: a first term comprising the slope between Vref and Vddq, and a second term comprising a Vref offset. Each of these terms can be independently adjusted in first and second modes: the slope term via the voltage divider, and the offset term by the magnitude of the injected current. Use of the disclosed Vref generator in one useful implementation allows Vref to be optimized at two different values for Vddq.