Development of Self-Calibrating A/D Converters

Until well after I thought of the self-calibration idea, I believed I was the first one to have recognized the property of the binary weighted capacitor array and exploited it to measure capacitor mismatch - nothing remotely similar had turned up in any of the circuit-type journal or conference publications. I discovered later, to my dismay, McCreary had thought of the same principle and had applied it to characterize capacitor mismatch characteristics [9]. This had been published in IEEE Transactions on Instrumentation and Measurements in 1979 - a journal I had not thought was relevant to data converters. Of course, McCreary used the principle for capacitor matching characterization, not for calibrating ADC´s, but he recognized the important symmetry in a binary weighted capacitor array and used it to measure capacitor mismatch. Along with his pioneering work in charge-redistribution ADC´s, his work laid the foundation for the self-calibrating ADC work presented here. The self-calibrating ADC improved its own accuracy without a factory calibration or a golden standard for the first time. Many other calibration methods followed for various different types of ADC´s including successive-approximation, pipeline, and delta-sigma ADC´s, ultimately finding applications in other analog circuits in the form of now popular digitally-assisted analog circuits.