Patent ID: 6587815
Filing Date: 2003-07-01
Classification: G06F

Abstract:
A method for detecting and analyzing effects of noise in a digital circuit, the method comprising:providing M selected circuits, numbered mâ€²=1, 2, . . . , M, that are electrically connected together, each circuit having at least one semiconductor gate, where M&gE;2; providing a wraparound sequence of N consecutive window intervals of selected temporal lengths, with N&gE;4, where each group of three consecutive window intervals, referred to as a window group interval, includes at least one of the following time intervals: an estimated time interval &Dgr;t(pulse) required for a second circuit to switch from within x1 percent of a second circuit initial voltage value to within x2 percent of a second circuit final voltage value, in response to switching of a first circuit, where x1 and x2 are selected numbers satisfying 01,in(t) at the at least one gate in the first circuit, and an estimated time interval &Dgr;t(skew) for uncertainty in accuracy in time provided by a clock signal used to synchronize time for at least one circuit; introducing the voltage input signal, V1,in(t), into the first circuit within a selected window interval, allowing the at least one gate in the first circuit to switch from a first state to a second state within a selected window group interval, and estimating a time interval TIm, beginning at the time the input signal V1,in(t) is introduced, within which at least one gate of a circuit numbered m=2, . . . , M switches from a circuit m first state to a circuit m second state and produces a voltage output signal, denoted Vm,out(t); computing a combined voltage output signal Vc,out(t) as a sum of the output voltage signals Vm,out(t) (m=2, . . . , M) for which the estimated time interval TIm lies within the selected window group interval; determining whether the combined voltage output signal Vc,out(t) satisfies at least one of first, second and third selected noise propagation criteria for the first circuit, namely max{Vc,out(t)}&gE;VN,prop,max,1=max{V1,in(t)}âˆ’{margin},â€ƒâ€ƒ(1) max{Vc,out(t)}&gE;VN,prop,max,c=&khgr;Â·Vdd,â€ƒâ€ƒ(2) andâˆ«{Vc,out(t)âˆ’Vthr}2dt&gE;EN,max,&Dgr;t(noise)â€ƒâ€ƒ(3) where {margin} is a selected margin voltage, &khgr; is a selected fraction satisfying 0dd is a maximum voltage supplied to at least one of the circuits, Vthr is a selected threshold voltage and EN,max is a selected energy value; andwhen at least one gate in at least one circuit m=2, . . . , M switches within the selected window group interval and the combined voltage output signal Vc,out(t) satisfies at least one of the first, second and third noise propagation criteria for the first circuit, interpreting this response of the circuits m=2, . . . , M as permitting noise provided at a gate in the first circuit to propagate through at least one gate in at least one of the circuits m=2, . . . , M.