Total dose effects on negative voltage regulator

Functional failure at low dose level (4 Krad(Si)) on voltage regulators (LM137) from different manufacturers are analysed. Dose rate effects on parts hardness are evaluated, showing that lowering the dose rate degrade more the IC's in the range 55 rad(Si)/s- 0,8 rad(Si)/s A failure mechanism is proposed, mainly based on circuit analysis, voltage contrast measurements, local irradiation and local electrical measurements with probe station. A spice simulation was performed, providing quantitative informations on the degradation. In the light of such a failure analysis and dose rate effects, practical implications on radiation assurance are discussed.