Dynamic performance of a radiation tolerant 12B SAR ADC designed with a DGA-MOSFET

A radiation tolerant SAR ADC using Dummy Gate Assisted (DGA) n-MOSFETs is presented with a monotonic capacitor switching procedure. The prototype chip was fabricated using a commercial 0.35um CMOS technology and was designed for use in a sensor in space applications requiring high resolution, very low power consumption, and moderate speed. The calculated power consumption was 38uW under a 3.3V supply. The measured SNDR and SFDR were about 60.0dB and 65.0dB, respectively. The fabricated chip was irradiated by a Co-60 gamma ray with a dose of up to 300krad (Si), which corresponds to the total dose of a satellite in a geostationary orbit for 5 years. After irradiation, the ADC with conventional MOSFETs did not operate at all. However, the ADC with DGA MOSFETs could convert a signal into digital codes with only a small decrease in dynamic performance. This small degradation in dynamic performance is ascribed to the PIP capacitor composed of an ONO stack.