COMPARISON OF ERROR RATES IN COMBINATIONAL AND SEQUENTIAL LOGIC

A pulsed laser was used to demonstrate that, for transients much short er than the clock period, error rates in sequential logic were indepen dent of frequency, whereas error rates in combinational logic were lin early dependent on frequency. In addition, by measuring the error rate as a function of laser pulse energy for fixed crock frequency, the lo garithmic dependence of the SEU vulnerable time period prior to the cl ock edge in combinational logic was established. A mixed mode circuit simulator program was used to successfully model the dynamic response of the logic circuit to pulses of laser light.