Hardness assurance methods for radiation degradation of optocouplers

Hardness assurance methods are examined for several types of optocouplers. A new diagnostic method using reverse-recovery time has a strong correlation with damage in the internal light emitting diode (LED). It depends only on electrical measurements, and can be used as a first-order parameter to determine LED properties when the LED technology of the optocoupler is unknown, as well as for evaluating unit and lot variability. For devices with internal LEDs that are highly sensitive to displacement damage, the dependence of phototransistor gain on operating conditions can impact post-radiation performance. For devices with radiation-tolerant LEDs, phototransistor characteristics and gain degradation are both important in determining the net effect of displacement damage.