The CLKOUT and SYSREF outputs can be momentarily upset due to an ion strike. Signatures included a momentary change in the frequency or a loss of the output for a period time up to one microsecond. The outputs always returned to the programmed frequency and power. The DUT did not have to be reset or the registers reprogrammed after an SEU. The output can recover out of phase from the signal before the SEU. Figure 3-1 is an example of an SEU on SYSREF1 where the pulse momentarily broadened, but then returned to the proper frequency.

Figure 3-1 Example of SEU on SYSREF1