Power Supply Decoupling
The number one root cause of system related problems is due to inadequate power supply decoupling around the DSP and or other surrounding circuits such as DDR, clocks, analog-to-digital and digital-to-analog converters etc. The most challenging task for designers is to determine the best decoupling techniques to achieve low noise and high performance. In general, component manufactures provide a conservative recommendation for power supply decoupling, but in many cases, it is not practical to follow this recommendation because of PCB space availability, power consumption, EMI or safety requirements. Also, component manufactures always provide development platforms for designers to evaluate and these platforms typically are a lot larger than the actual design and are not required to be FCC certified, so copying what was done on the development platform is not a guaranteed that the design will be successful. This chapter will discuss three important topics for designers: 1. a general rule-ofthumb decoupling method, 2. an analytic decoupling method and 3. how to make design tradeoffs to achieve the best noise performance possible.
KeywordsEquivalent Series Resistance Ceramic Capacitor Parasitic Inductance Ball Grid Array Package Decoupling Capacitor
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