A Method for Measuring Vref Noise Tolerance of DDR2-SDRAM on Test Board Simulatig Actual Memory Module

Aiming to achieve double data rate-synchronous DRAM (DDR-SDRAM) at low-cost and with high noise tolerance by setting adequate Vref target impedance, we have established a measurement setup for Vref noise tolerance of DDR2-SDRAM on test board simulating actual memory module and measured various properties. The measured Vref noise tolerance has strong frequency-dependency; the higher the frequency, the larger the noise tolerance. We believe that this is because the intrinsic low pass filter consisted of on-chip electrical components in the test chip.