This paper describes the impact of DRAM-caused power noise (especially simultaneous switching output noise) in DDR2 667 system. The power noise is regulated by adjusting the package inductance of power delivery nets, DQ driver strength, and the power supply voltage. The package inductances of core power delivery net (VDD/VSS) and the DQ power delivery net (VDDQ/ VSSQ) are controlled by adjusting the number of solder balls on package. Also, the DQ power noise is controlled by adjusting DQ driver strength. The power supply level adjusts to control both core and DQ power noises. In summary, DRAM power noise is closely related to the radiated emission, and DRAM power noise should be properly controlled to reduce EMI in digital system.
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