Analysis of Near Field Radiation at LPDDR5 DRAM with Various Operation Modes

This paper investigates the primary source of Electromagnetic Interference (EMI) radiation at the chip level, a crucial step toward developing a low EMI chip. The study first seeks to determine which mode of Dynamic Random Access Memory (DRAM) radiates the most. An Automatic Test Equipment (ATE) with an Hz probe is utilized to measure the EMI in various DRAM modes. Results indicate that although the current level in Refresh mode is comparable to that of Write mode, its impact is minimal because the internal circuit operation of DRAM is below 50 MHz. The maximum EMI level was observed in write mode at the spectral line of the fundamental harmonics of Command and Address (CA) and Data (DQ) patterns, indicating a correlation with the peripheral circuit. Consequently, it was concluded that Read/Write mode is the predominant radiation mode and that the IO simultaneous switchings are primarily associated with chip-level EMI.