Observation of an ion-induced sustained high current condition (''high
current anomaly'') in a bipolar device, that is similar but not ident
ical to latchup, is reported. Both high current anomaly and single eve
nt upset test results are presented for the AD9048 test device. Photon
emission microscopy was used to locate the site of the high current a
nomaly. A model of the triggering mechanism based on the results so ob
tained is described.