Variable Series Resistance Termination for Wireline Serial Links
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Solution Overview
Problem
High-speed wireline serial links in integrated circuits face signal degradation due to impedance mismatches, which are exacerbated by parasitic capacitance from transistors used in conventional resistive tuning circuits, leading to data loss and reduced performance.
Innovation Solution
A resistive tuning circuit with series-connected resistive components and controlled by transistors to minimize parasitic capacitance, allowing for variable impedance adjustment to match transmitter and receiver impedances, thereby reducing reflections and signal degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If transistors are used in resistive tuning circuits to adjust impedance, then impedance matching capability is improved, but parasitic capacitance increases causing signal degradation
Solution Approach 1:
The patent extracts and removes the transistors from the resistive tuning circuit, replacing them with transistor-independent switching mechanisms. This eliminates the parasitic capacitance generated by transistors while preserving the impedance adjustment functionality through alternative circuit topologies that use passive components and switching devices with minimal parasitic effects.
Solution Approach 2:
The patent introduces intermediary switching devices (such as transmission gate switches or passive switches) that act as mediators between the resistive components and the signal path. These intermediary devices provide the necessary switching functionality for impedance adjustment without introducing the harmful parasitic capacitance associated with transistors.
2Reliability
If conventional FIR filter with parallel resistive components is used for channel equalization, then equalization performance is improved, but return loss increases due to capacitive component
Solution Approach 1:
The patent changes the configuration of resistive components from parallel to series arrangements in the FIR filter implementation. This parameter change in circuit topology reduces the overall capacitive component effect at high frequencies, thereby reducing return loss while maintaining the channel equalization functionality through adjusted filter coefficient implementation.
3Device complexity
If resistive tuning circuit uses same resistive components as FIR filter, then device complexity is reduced, but signal degradation increases due to transistor parasitic capacitance
Solution Approach 1:
The patent segments the resistive tuning circuit and FIR filter into separate implementations, allowing the FIR filter to use shared resistive components while the resistive tuning circuit uses dedicated components with minimal parasitic effects. This segmentation enables independent optimization of each function, reducing signal degradation while managing device complexity through systematic component allocation.
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
The solution effectively reduces parasitic capacitance, minimizing signal reflections and improving data transmission quality by dynamically adjusting the resistive component of the impedance to match the transmitter and receiver, enhancing the reliability and speed of high-speed wireline serial links.
Implementation Method 1
resistive tuning circuit to optimize the resistive component of the output impedance to reduce return losses
Implementation Method 2
degradation by imperfect return loss caused by reflection of a portion of the signal at a discontinuity such as an impedance mismatch
Implementation Method 3
The presence of these transistors incurs a parasitic capacitance, which increases the high-frequency return loss and degrades the transmitted signal
Data Source
AI summary
A variable series resistance termination circuit for wireline serial link transceivers is provided. Some embodiments include a pad for coupling to a wireline serial link and a termination circuit. The termination circuit includes a plurality of resistive components coupled in series with the pad and a plurality of switches. Each switch is to couple one or more of the plurality of resistive components in series between the pad and a termination voltage node when the switch is closed. A subset of the plurality of switches can be selectively closed to establish a resistive component of an impedance of the termination circuit.