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This paper proposes a digital background calibration scheme for timing skew in time-interleaved analog-to-digital converters (TIADCs). The timing error is detected by using the first derivative of the channel ADCs and a least-mean-square (LMS) loop is exploited to compensate the timing skew. The proposed scheme is effective within the entire frequency range of 0–f_s/2. Compared with traditional calibration schemes, the proposed approach is more feasible and consumes lesser power and smaller area.

Time-interleaved technique is widely used to increase the sampling rate of analog-to-digital converter (ADC). However, the channel mismatches degrade the performance of time-interleaved ADC (TIADC). When input signal frequency is very high, timing skews have significant effect on distortion. Therefore, a new timing skew calibration method is proposed in this paper. This method is based on the truth that timing skews are related to the product of the outputs of sub-ADCs. After timing skews are estimated, the digital controlled delay elements (DCDE) in ADC and phase locked loop (PLL) are utilized to calibrate timing skews. No auxiliary circuit and digital filter are needed for this calibration method. Simulation results show that the proposed method can estimate timing skew accurately. It is also proved that an accurate estimation can be obtained even the signal to noise ratio (SNR) of input signal is 20dB. The proposed method is employed to calibrate timing skews in a 16-channel TIADC-based 20GSPS digital storage oscilloscope (DSO). The experiment results demonstrate the usefulness of the proposed method. We can see that after timing skews are calibrated, the spectrum spurs have been effectively eliminated.

This paper presents a 32-GS/s front-end sampling circuit (FESC) in 65-nm CMOS. The FESC is designed for a 32-channel time-interleaved analog-to-digital converter (ADC), and the $4\times 8$ two-stage interleaving structure leads to a good trade-off between bandwidth and linearity. The analysis and cancellation of charge injection, clock feedthrough, and signal feedthrough are presented. Inductor peaking technique is adopted to extend the bandwidth of the buffer between the first and the second stage. Based on the simulation results, the proposed FESC consumes 136mW at 32 GS/s, and the signal-to-noise ratio (SNDR) is up to 39.55 dB at Nyquist input, achieving a state-of-the-art power efficiency.