Calibration requires calibration, a case study: Mixed-signal BISC Time-Interleaved ADC

Modern electronic systems claim for Analog-to-Digital (A/D) interfaces with strong requirements in terms of resolution and frequency. Among several A/D architectures that intent to achieve these hard specifications, Time-Interleaved Analog-to-Digital Converters (TIADC) arises as a competitive candidate. TIADC offer a higher sampling frequency with suitable moderate power consumption. However, their architecture introduces mismatch errors that affect the resolution of data conversion. Calibration methods permit to reduce significantly the impact of these errors. A possible solution is the insertion of an additional circuitry in the A/D conversion system: a Built-In Self-Calibration (BISC). A BISC system aims to compensate imperfections from the TIADC, such as offset, gain and timing errors. Despite the benefits carried by the BISC, this system also introduces errors in the overall data conversion system. This paper proposes a case study of a mixed-signal BISC TIADC, highlighting the strengths and the weakness of using built-in calibration circuits. Supplementary calibration methods will be explored to mitigate the impact of the BISC and to improve the A/D conversion performance. The debate is open: how calibration systems must be calibrated?