Comparison of gamma radiation performance of a range of CMOS a/D converters under biased conditions

Radiation effects on analog and mixed signal semiconductor devices are a major concern in space and nuclear applications. Significant degradation has been observed in A/D converters in a radiation environment. In fact, recent advances in A/D converters have further reduced the radiation tolerance of these converters on account of their complex circuitry. This paper studies the effects of gamma radiation on several properties (offset error, gain error, integral non linearity etc.) of a whole range of A/D converters under biased conditions. A comparative study of their performance is presented. Four major types of A/D converters, namely- flash, successive approximation, integrating and sigma-delta type, are selected for a detailed evaluation and comparison. Significant degradation of the power supply currents was observed in the biased samples during radiation. Significant improvement in radiation tolerance after adjustment of the offset and calibration registers in the high resolution sigma delta converters can be achieved. All the results and experimental observations are presented.