TY - JOUR

T1 - Analysis of effect of feedback current variation in CT Delta-Sigma modulators with Gm-C integrators

AU - Tang, Hua

PY - 2017/12/1

Y1 - 2017/12/1

N2 - In design of Continuous-time Delta-Sigma modulators, the feedback DAC (Digital-to-Analog Converter) is typically implemented with a switched current circuit. It is desired that these DAC current circuits provide constant current across clock cycles for each modulator output level. However, when Delta-Sigma modulators are implemented with Gm-C integrators, the DAC feedback current circuits are directly connected to the integrator outputs that may have high-swing voltages and this results in varying DAC feedback current. In this paper, we analyze the effect of feedback current variation caused by high-swing integrator output voltages in Delta-Sigma modulators built with Gm-C integrators. It is shown that feedback current variation may significantly degrade the performance of Delta-Sigma modulators mainly due to the non-linearity of current variation dependence on the integrator output voltage, while mismatch of current variation has minor effect.

AB - In design of Continuous-time Delta-Sigma modulators, the feedback DAC (Digital-to-Analog Converter) is typically implemented with a switched current circuit. It is desired that these DAC current circuits provide constant current across clock cycles for each modulator output level. However, when Delta-Sigma modulators are implemented with Gm-C integrators, the DAC feedback current circuits are directly connected to the integrator outputs that may have high-swing voltages and this results in varying DAC feedback current. In this paper, we analyze the effect of feedback current variation caused by high-swing integrator output voltages in Delta-Sigma modulators built with Gm-C integrators. It is shown that feedback current variation may significantly degrade the performance of Delta-Sigma modulators mainly due to the non-linearity of current variation dependence on the integrator output voltage, while mismatch of current variation has minor effect.

KW - Continuous-time

KW - Delta-Sigma modulators

KW - Feedback current variation

KW - Gm-C integrators

KW - Mismatch

KW - Non-linearity

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U2 - 10.1007/s10470-017-1049-5

DO - 10.1007/s10470-017-1049-5

M3 - Article

AN - SCOPUS:85030657308

SN - 0925-1030

VL - 93

SP - 467

EP - 476

JO - Analog Integrated Circuits and Signal Processing

JF - Analog Integrated Circuits and Signal Processing

IS - 3

ER -