Xilinx Zynq-7000 Design Manual

Also see for Zynq-7000: Quick start guide Getting started guide User guide Application note User guide

Zynq-7000 PCB Design Guide www.xilinx.com 34UG933 (v1.8) November 7, 2014Chapter 3: Power Distribution SystemThe measurement shown in Figure 3-8 and Figure 3-9 represents the peak-to-peak noise. Ifthe peak-to-peak noise is outside the specified acceptable voltage range, the decouplingnetwork is inadequate or a problem exists in the PCB layout.3.0.1 Noise Spectrum MeasurementsHaving the necessary information to improve the decoupling network requires additionalmeasurements. To determine the frequencies where the noise resides, noise powerspectrum measurement is necessary. A spectrum analyzer or a high-bandwidth oscilloscopecoupled with FFT math functionality can accomplish this.The FFT math function can be built into the oscilloscope, however, many of these functionsdo not have resolution sufficient to give a clear picture of the noise spectrum. Alternatively,a long sequence of time-domain data can be captured from an oscilloscope and convertedto frequency domain using MATLAB or other post-processing software supporting FFT. Thismethod has the advantage of showing as much resolution as the user is willing to process.If neither math capacity is available, the noise frequency content can be approximated byvisually examining the time-domain waveform and estimating the individual periodicitiespresent in the noise.A spectrum analyzer is a frequency-domain instrument, showing the frequency content of avoltage signal at its inputs. Using a spectrum analyzer, the user sees the exact frequencieswhere the PDS is inadequate.X-Ref Target - Figure 3-9Figure 3-9: Infinite Persistence Measurement of Same SupplyUG933_c3_09_032811Send Feedback