Analog Calibration of Mismatches in an Open-Loop Track-and-Hold Circuit for Time-Interleaved ADCs

This paper presents a method for the on-chip measurement and correction of gain errors, offsets and nonlinearities of a track-and-hold circuit (T&H) of an ADC. Open-loop T&H circuits were considered in this paper because of their high-speed and low-power capabilities. However, these open-loop circuits require calibration for the aforementioned errors in order to achieve a high accuracy, especially in case of time-interleaved architectures. With the proposed method, the errors can be measured and digitized on-chip accurately, without requiring a substantial amount of hardware or any accurate references. Then, this information is used by a digitally implemented algorithm to optimize several digitally controlled analog parameters of the circuit. In turn, these parameters minimize the effect of mismatch errors. After optimization, the digital logic can be switched off completely in order to save power.