PCB Open Stub Wiring for DDR3 Signal Ringing Suppression
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Solution Overview
Problem
In high-functional electronic devices using DDR3-SDRAM memory systems, the long branch wiring lengths lead to signal attenuation and reflection issues, causing waveform turbulence and ringing problems, especially when mounting pads are densely arranged, making it difficult to satisfy the input voltage condition of address/command signals.
Innovation Solution
The implementation of a printed circuit board with a main wiring and branch wirings connected through open stub wiring configurations, which includes a first and second open stub wiring to manage signal reflections and attenuate ringing by overlapping reflected waves with direct waves at specific branch points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the mounting pads are arranged at high density to increase memory capacity, then the quantity of memory devices increases, but the branch wiring length becomes long causing signal attenuation and ringing
Solution Approach 1:
The patent introduces an open stub wiring as an intermediary element between the main wiring and branch wiring. This open stub wiring acts as a mediator to cancel out negative reflections by creating positive reflections that overlap with and counteract the harmful signal reflections, thereby maintaining signal quality even when branch wiring length increases due to high-density mounting pad arrangement.
Solution Approach 2:
The open stub wiring is configured to generate positive reflections in advance that preemptively counteract the negative reflections before they can cause significant signal degradation. By positioning the open stub wiring at specific locations and lengths, the patent creates a preliminary anti-action that cancels out the harmful effects of long branch wiring before they propagate through the signal path.
2Length of stationary object
If the via hole is arranged adjacently to the mounting pad to shorten branch wiring, then the wiring length is reduced, but the via hole cannot be arranged between densely spaced mounting pads
Solution Approach 1:
The patent segments the branch wiring into two parts: the extraction wiring connecting the via hole to the mounting pad, and the open stub wiring connecting to the main wiring. This segmentation allows the via hole to be positioned flexibly - it can be adjacent to the mounting pad when space permits, or positioned elsewhere when mounting density requires it, without compromising overall signal integrity due to the compensating open stub wiring.
Solution Approach 2:
The patent changes the parameters of the wiring configuration by introducing the open stub wiring with specific length and positioning parameters. This allows the system to adapt to different mounting densities - when pads are densely spaced, the open stub wiring compensates for the necessarily longer extraction wiring, maintaining signal quality across varying physical configurations.
3Ease of manufacture
If the branch wiring length becomes long due to via hole positioned outside mounting pads, then manufacturing flexibility increases, but signal attenuation and reflection become serious
Solution Approach 1:
The open stub wiring serves as a mediator that compensates for the signal degradation caused by long branch wiring. By introducing this intermediary element with controlled impedance and specific length, the patent cancels out the negative reflections that occur due to long extraction wiring, thereby maintaining signal waveform stability even when via holes are positioned for manufacturing convenience rather than optimal signal performance.
4Reliability
If the open stub wiring is added to suppress signal reflection, then signal quality improves, but device complexity increases
Solution Approach 1:
The open stub wiring is a relatively simple intermediary structure that can be integrated into existing PCB designs without fundamentally changing the overall wiring architecture. By adding this single compensating element rather than redesigning the entire wiring system, the patent achieves signal quality improvement with minimal increase in device complexity.
Solution Approach 2:
The patent optimizes the parameters of the open stub wiring (length, position, impedance) to achieve effective reflection cancellation with the minimum necessary structure. By carefully selecting these parameters, the solution suppresses signal reflection using the simplest possible configuration, thereby limiting the increase in device complexity while maintaining signal waveform stability.
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 configuration effectively suppresses signal ringing across varying branch wiring lengths, ensuring the input voltage condition is met and maintaining signal quality by attenuating negative reflections and improving waveform stability.
Implementation Method 1
the printed wiring board includes a first open stub wiring having a first connecting end electrically connected to a first connecting point on the main wiring between a start end and a first branch point, and a first open end, the other end, which is opposite to the first connecting end
Data Source
AI summary
A memory system is provided with a motherboard, and a memory controller and a plurality memory devices mounted on the motherboard. The motherboard comprises a unicursal-shape main wiring, and branch wirings branched from the main wiring to the respective memory devices. Further, the motherboard comprises an open stub wiring branched from a connecting point between a start end and a branch point of the main wiring. Thus, a ringing of a waveform of a signal received by a receiving circuit can be suppressed irrespective of a wiring length of the branch wiring.