Aerospace PCB Layout for Dual DDR2 Memory Bandwidth
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Solution Overview
Problem
Existing printed circuit boards used in space applications are hindered by outdated DDR1 SDRAM memory technology, which is no longer suitable due to end-of-life issues and insufficient memory bandwidth, requiring an upgrade to support increased data processing demands, especially for image processing applications.
Innovation Solution
A radiation-hardened single board computer system with a unique layout featuring dual double data rate synchronous dynamic random-access memories (DDR2 SDRAMs) on both sides of the printed circuit board, reducing operating voltage and enabling a high-performance reconfigurable FPGA for enhanced data processing capabilities, along with a symmetrical layer stack-up and back-to-back component configuration to minimize dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DDR1 SDRAM memory is used in the printed circuit board, then the system can maintain compatibility with existing space-qualified components, but the memory bandwidth is insufficient for modern data processing demands
Solution Approach 1:
The patent transitions from DDR1 to DDR2 SDRAM technology, changing the memory interface parameters including data rate, voltage levels (1.8V vs 2.5V), and signal timing characteristics. This parameter change enables higher memory bandwidth while the design accommodates the new parameters through updated PCB trace impedance control and signal integrity measures
2Productivity
If DDR2 SDRAM with new interface signals and voltage requirements is implemented, then memory bandwidth increases, but the printed circuit board design complexity increases
Solution Approach 1:
The patent employs a multi-layer PCB architecture with specific layer stacking to accommodate DDR2 interface requirements. By utilizing multiple PCB layers with controlled impedance traces and proper signal routing, the design manages the increased interface complexity while maintaining signal integrity for high-speed DDR2 operations
3Productivity
If high-performance FPGA and DDR2 SDRAM components are used, then processing capacity increases to 3,000 MIPS, but power consumption increases
Solution Approach 1:
The patent utilizes DDR2 SDRAM's lower operating voltage (1.8V compared to DDR1's 2.5V) to reduce power consumption. By changing the voltage parameter and optimizing the power distribution network with dedicated power layers and decoupling capacitors, the system achieves high processing capacity while managing power requirements more efficiently
4Area of stationary object
If components are arranged in back-to-back configuration, then the printed circuit board dimensions are minimized, but signal routing complexity increases
Solution Approach 1:
The patent uses a multi-layer PCB structure to route signals for back-to-back mounted components. By utilizing vertical layer transitions and through-hole vias, the design achieves compact horizontal footprint while managing signal routing complexity through the third dimension (PCB layers), allowing proper signal integrity maintenance in a minimized area
Data Source
AI summary
The present invention relates to a single board computer system with an improved memory and layout. The unique layout of the printed circuit board of the present invention allows for different parts to be placed in a back-to-back configuration to minimize the dimensions of the printed circuit board. This includes a high-performance radiation-hardened reconfigurable FPGA, for processing computation-intensive space systems, disposed on both sides of the printed circuit board. Four dual double data rate synchronous dynamic random-access memories (DDR2 SDRAMs) disposed on both the top side and on the bottom side of the printed circuit board reduce an operating voltage of said printed circuit board. A layout stack-up of the printed circuit board includes twenty-two symmetrical layers including ten ground layers, four power layers, six signal layers, a top layer, and a bottom layer.