A 12-Bit Time-Interleaved 400-MS/s Pipelined ADC with Split-ADC Digital Background Calibration in 4,000 Conversions/Channel

Split analog-to-digital converter (ADC) digital background calibration with full-input-range error detection schemes is proposed to rapidly correct the gain and nonlinearity errors in the multi-bit first stage of a multi-channel time-interleaved (TI) pipelined ADC. By adding a vertical shift between the residue transfer curves of the first stages in two half-ADCs which are split from a single ADC, the error detection schemes of the proposed calibration are effective in the full-input range. The larger error detection range means that calibration is activated more often, resulting in fewer ADC conversions to converge. In addition, the designed fast-settling switch controller enables a 12-bit resistor-ladder DAC (R-DAC) for high-speed application. Furthermore, by applying the proposed calibration and sharing the R-DAC among all channels, the need for gain mismatch calibration between interleaved channels is eliminated. Consequently, the calibration time and complexity are further reduced. A 12-bit 400-MS/s 4-channel TI pipelined ADC prototype is implemented in 40-nm CMOS technology with an active area of 0.71 mm², the measured SNDR and INL of which are improved up to 23 dB and 96 LSB via the proposed calibration. Compared with prior-art ADCs using background calibration, the proposed ADC achieves the fastest background calibration in 4,000 conversions/channel, which is at least 5× less than the others.