Pipelined Successive Approximation Conversion (PSAC) with Error Correction for a CMOS Ophthalmic Sensor

The purpose of this work is the proposal of a 10-Bit / 1 MSPS Analog to Digital Converter (ADC) with error correction to match the requirements of a CMOS wavefront sensor for ophthalmic applications. The developed ADC is a combination of different techniques for integrated converters. It unifies the advantages of successive approximation converters and pipelined converters. The result of this combination is a very good tradeoff between performance and power dissipation. In a second step, the problem of parameter variations is examined. Therefore, the developed ADC is enhanced by two error correction techniques to improve its reliability. Transistor level simulations indicate that in an environment with varying design parameters the maximum (Differential Non-Linearity) DNL error could be reduced from more than 130 V LSB to 0.7 V LSB. The ADC selection assessment and error correction presented herein can be adopted for other sensors within other signal domains as well