This paper presents a simple compensation scheme for extending the stable input range of a single-bit sigma-delta (Σ-Δ) modulator that is normally stabilized in sliding mode. The proposed control scheme requires a saturation element that provides additional feedback to modify and stabilize the modulator loop filter when the modulator is going to lose stability due to large input level. | Journal of Automation and Control Engineering, Vol. 1, No. 1, March 2013 Extending the Stable Input Range of a Single-Bit Sigma-Delta Modulator with a Saturation Element Shiang-Hwua Yu and Ming-Hung Tseng Department of Electrical Engineering, National Sun Yat-Sen University, 70 Lien-Hai Road, Kaohsiung, 804, Taiwan E-mail: shaun@ Abstract—This paper presents a simple compensation scheme for extending the stable input range of a single-bit sigma-delta (Σ-Δ) modulator that is normally stabilized in sliding mode. The proposed control scheme requires a saturation element that provides additional feedback to modify and stabilize the modulator loop filter when the modulator is going to lose stability due to large input level. The proposed compensation scheme is easy to implement and is only activated when the input level is exceedingly large, so it does not affect the performance of the modulator with its input in the normal range. A third-order sigma-delta modulator with an extended input range was designed and implemented to demonstrate the practicality of the proposed design. automatically tuned according to the peak value of the input signal. This study developed a compensation scheme for a single-bit sigma-delta modulator operated in sliding mode [10]. The compensation scheme is activated to stabilize the modulator when some internal signal of the loop filter goes beyond some limit prescribed by the stability condition of sliding mode, thereby widening the stable input range without scarifying the desired performance. An illustrative design example shows the effectiveness of this easy-to-use compensation scheme. Index Terms—dynamic range, input range, over-sampling A/D converter, sigma-delta modulator, sliding mode. (a) I. INTRODUCTION A single-bit sigma-delta modulator consists of a two-level clocked quantizer and a linear filter in feedback connection, as shown in Fig, 1(a). Sigma-delta modulators have been widely applied in data .
