Decoupling capacitor effects on switching noise

The experimental procedures and test vehicles used for the characterization of the decoupling capacitor efficiency in reducing the power supply differential switching noise of the multichip-module (MCM) package structure employed in the IBM ES/9000 system are described. The experimental results are summarized for various switching elements. It is demonstrated that careful design of the test vehicles, tester systems, and probes makes the accurate measurement of Delta-1 noise feasible. Experimental results on the BOBCAT tester show that the decoupling capacitor efficiency in reducing the peak of the differential Delta-1 noise is 50-67%. This efficiency can be increased by reducing the effective inductance in the decoupling capacitor current return path.<
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