
10%-90% variations
• As designs move to smaller process technology the
edge rates are increasing
• USB 2.0 specification limits RT/FT to 500ps as
measured at 10%-90%
• Errors in consistency of these measurements due to:
– Shape of signal edge
– Noise
– Amplitude variations
– Probe peaking due to insufficient BW
• Slow corners give 10/90
rise time that is slower than
actual edge rate
• RT/FT faster than 400ps have observed
• Oscilloscope AND Probe BW must be at least 2.5Ghz
to accurately observe and measure these fast edges
Rise and Fall time
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