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noise analysis with Encounter Timing Sysytem

KVBABU

Hi All,

Iam new to Encounter timing System tool and iam trying to perform noise analysis using this. I had gone ETS userguide, wher i found that , a violation is determined by comparing the receiver peak voltage value to the receiver’s voltage threshold value (25 percent of VDD for sequential cells and 80 percent of VDD for combinatorial cells).

could any one of you explain the why this threshold is 25% of VDD for sequential and where as it is 80% of VDD for combinational cells?

Regards,

K.VISWANADH BABU

  • sambasiva

    Evandi Viswnadh babu garu

    Main purpose of crosstalk analysis is to see any functionality issue is there because of coupling.

     Actually if we set the threshold value of 25%vdd to combi cells then we are in more pesimestic mode.

    Because for example consider a path where there are 4 levels of combigates and finally going to flop.For suppose there is a glitch at first level but traversing through the remaing levels and by the time reaching the flop that glitch magnitude can be less/high(for suppose less) then there is no issue making the threshold value to high value when compared to sequentional ones.

    any how threshold value is descided by noise margin.  

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