Silicon Laboratories Inc.
Successive-approximation analog-to-digital converter gain calibration using floating capacitors

Abstract:

A successive-approximation ADC includes an input capacitance coupled to a first node and configured to store a sampled input charge based on an input analog signal during a first phase of an analog-to-digital conversion. A gain tuning capacitance configured to store a first portion of the sampled input charge during a second phase of the analog-to-digital conversion. A charge-redistribution DAC includes a conversion capacitance configured to store a second portion of the sampled input charge during the second phase and configured to use the second portion, a remaining portion of the sampled input charge, and a reference voltage to provide an analog signal on the first node corresponding to a digital output code approximating the input analog signal at an end of the third phase. The gain tuning capacitance sequesters the first portion of the sampled input charge from the charge-redistribution DAC during the third phase.