PCB Signal Path Damping for Memory Reflection Control
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Solution Overview
Problem
Electronic apparatuses with multiple memories face increased electromagnetic interference (EMI) due to reflection effects at signal paths, particularly when memories without on-die termination (ODT) are accessed, leading to power consumption increases and antenna effects from floating stubs on printed circuit boards (PCBs).
Innovation Solution
The implementation of a printed circuit board (PCB) design with strategically placed damping devices on longer signal paths between controllers and memories without ODT, where the distance between the damping device and the branch point is optimized to reduce reflections and adjust signal strength, eliminating the need for termination devices and floating stubs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If termination devices are disposed on the PCB for I/O pins without ODT, then reflection effects are reduced, but power consumption increases due to leakage
Solution Approach 1:
The patent applies different termination strategies to different signal paths based on their specific characteristics. ODT is applied only to I/O pins that require it, while damping devices are selectively placed only on longer signal paths that exhibit reflection problems. This localized approach avoids the need for universal termination devices that would consume excessive power, thereby reducing overall power consumption while still addressing reflection effects where they actually occur.
Solution Approach 2:
The patent changes the termination parameter from traditional parallel or series termination devices to damping devices with specific resistance values (e.g., 22 ohms, 33 ohms, or 47 ohms) strategically positioned on longer signal paths. This parameter change allows for effective reflection reduction without the continuous power consumption associated with traditional termination devices, as the damping devices are designed to have minimal impact on power usage while effectively controlling signal reflections.
2Use of energy by moving object
If termination devices are not disposed on the PCB, then power consumption is reduced, but floating stubs cause reflections due to the antenna effect
Solution Approach 1:
The patent implements damping devices only on longer signal paths that are prone to reflection issues, while leaving shorter signal paths without additional termination components. This selective local treatment eliminates the need for universal termination devices, thereby maintaining low power consumption, while still addressing the antenna effect and floating stub reflections on the specific signal paths where they occur.
Solution Approach 2:
The damping devices serve as intermediary elements between the I/O pins and the rest of the circuit. These devices act as mediators that absorb and dampen reflections from floating stubs and antenna effects without requiring continuous power consumption, effectively bridging the gap between the need for reflection control and the desire for low power usage.
3Quantity of substance
If multiple memories are implemented in an electronic apparatus, then data storage capacity increases, but electromagnetic interference and reflection effects increase
Solution Approach 1:
The patent applies damping devices selectively to specific signal paths based on their length and susceptibility to reflection, rather than uniformly to all memory interfaces. This localized approach allows multiple memories to be implemented with increased data storage capacity while minimizing electromagnetic interference and reflection effects only where they are most problematic, thus balancing storage expansion with EMI control.
Solution Approach 2:
The patent uses partial termination by applying damping devices only to the extent necessary on longer signal paths, rather than implementing full termination across all memory interfaces. This partial action is sufficient to control reflections and EMI in multi-memory configurations without over-terminating, which would unnecessarily increase power consumption and complexity.
4Ease of manufacture
If series termination is used on the PCB, then cost is reduced compared to parallel termination, but power consumption increases due to leakage
Solution Approach 1:
The patent changes the termination parameter by using damping devices with specific resistance values (22 ohms, 33 ohms, or 47 ohms) on longer signal paths instead of traditional series or parallel termination devices. This parameter change maintains the cost advantage of simple PCB implementation while significantly reducing the power consumption associated with leakage, as the damping devices are designed to have minimal impact on power usage.
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 design effectively reduces reflections and power consumption by attenuating signals on longer paths, improving signal quality and reducing skew, resulting in a wider eye-opening in signal diagrams for near-end devices.
Implementation Method 1
a first damping device disposed on the second signal path... The first damping device is disposed between the second finger and the first branch point
Data Source
AI summary
An electronic apparatus is provided. The electronic apparatus includes a printed circuit board (PCB) with a first signal path and a second signal path therein, a first finger disposed on the first signal path, a second finger disposed on the second signal path, a controller disposed on the PCB and coupled to a first memory via the first finger and to a second memory via the second finger, and a damping device disposed on the second signal path. The first and second signal paths share a common segment between the controller and a branch point on the PCB. The damping device is disposed between the second finger and the branch point. The distance between the first finger and the branch point within the first signal path is smaller than the distance between the second finger and the branch point within the second signal path.