A Low-Power Second-Order Two-Channel Time-Interleaved ΣΔ Modulator for Broadband Applications

概要

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Time-interleaving is an efficient approach to increase the effective sampling rate of the ΣΔ modulators, but time-interleaved (TI) ΣΔ modulators are sensitive to channel mismatch, which causes the quantization noise folded back into the band of interest. To reduce the folded noise caused by the channel mismatch of two-channel TI ΣΔ modulators, a low-power second-order two-channel TI ΣΔ modulator is proposed. The noise transfer function (NTF) of the modulator is a band-pass filter. By using this band-pass NTF, the folded noised can be reduced. The entire modulator can be implemented by employing three op-amps, which is beneficial for power consumption. The circuit of implementation for the proposed modulator is designed in 0.18µm COMS technology. The proposed modulator can achieve a SNDR of 78.9dB with a channel mismatch of 0.5% and a linear gradient mismatch of 0.4% for unity sampling capacitors. Monte Carlo simulation is done with a random Gaussian mismatch of 0.4% standard deviation for all capacitors, resulting in an average SNDR of 80.5dB. It is indicated that the proposed TI modulator is insensitive to the channel mismatch. The total power consumption is 19.5mW from a 1.8V supply.
（社）電子情報通信学会の論文
2009-06-01