The reliability of systems used in space, avionic and biomedical applications is highly critical. Such systems consist of an analog front-end to collect data, an ADC to convert the collected data to digital form and a digital unit to process it. The reliability of these systems is affected by the ability of its constituent blocks to tolerate faults. Therefore, it is necessary to increase the reliability of ADCs to ensure a highly reliable critical system. This paper illustrates the steps involved in the reliability enhancement of ADCs by first proposing a methodology for fault sensitivity analysis and then illustrating redesign techniques to improve the reliability of the highly sensitive(to faults) blocks.