DDR Memory Data Scrambling for EMI Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for attenuating electromagnetic interference (EMI) effects in double-data-rate memory systems, such as DDR memories, are either ineffective or costly, particularly when dealing with horizontal repetition of data patterns that cause energy spikes and interfere with neighboring electronic systems like Wi-Fi antennas.
Innovation Solution
A method and device that scramble and unscramble data using a pseudo-random bit-key generated based on the memory address, applying an EXCLUSIVE OR logic function to each word, which breaks the correlation between consecutive bits and reduces EMI by over 20 dB in relevant frequency channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If data is transferred in parallel high-data-rate link to DDR memory, then data transfer speed is improved, but electromagnetic interference effects increase due to horizontal pattern repetition
Solution Approach 1:
The patent applies a scrambling function that changes the parameter of data bit distribution by using a pseudo-random sequence generated from the memory address. This transformation modifies the horizontal pattern repetition characteristics while maintaining the same data transfer rate, thereby reducing EMI effects without sacrificing speed performance
Solution Approach 2:
The patent introduces a pseudo-random sequence as an intermediary element between the original data and the transmitted signal. This sequence, generated based on the memory address, acts as a mediator that breaks the correlation between consecutive data bits while preserving the integrity and speed of data transfer
2Object-generated harmful factors
If electromagnetic shielding is used to attenuate EMI effects, then electromagnetic interference is reduced, but production cost increases
Solution Approach 1:
The patent replaces the mechanical/physical approach of electromagnetic shielding with a logical/scrambling approach. Instead of using physical barriers to block EMI, the system uses a data transformation technique that prevents the generation of EMI-causing patterns in the first place, thereby eliminating the need for expensive shielding materials and assembly
Solution Approach 2:
The patent employs a software-based scrambling function that uses simple pseudo-random number generation algorithms. This approach uses computationally inexpensive operations (XOR with address-based sequences) rather than expensive physical shielding materials, making the solution economically viable for mass production
3Object-generated harmful factors
If slew rate control is applied to clock signals, then electromagnetic interference is reduced, but transmission performance characteristics deteriorate
Solution Approach 1:
Instead of controlling the clock signal characteristics (slew rate) to reduce EMI, the patent inverts the approach by controlling the data pattern itself. The scrambling function modifies the data bits before transmission, preventing the generation of EMI-causing horizontal patterns while leaving the clock signal and transmission performance unchanged
Data Source
AI summary
A method for reading or writing data at an address of a memory is disclosed. The data includes a number of consecutive words that each has a plurality of bits. The words are transferred to or from the memory in synchronization with a clock signal so that each word is transferred in one cycle of the clock signal. The bits are scrambled or unscrambled by applying a logic function to the bits of each word. The logic function is identical for the scrambling and the unscrambling and makes use of a bit-key that is dedicated to the word and is identical for the scrambling and the unscrambling. Each bit-key comes from a pseudo-random series generated based on the address.