A 3.3 V, 10 Bits, Clock-Feedthrough Compensated Switched-Current Second Order Sigma-Delta Modulator

This article presents a low-pass sigma-delta modulator for Analogue-to-Digital conversion. The circuit uses a switched-current technique which presents a well known drawback called clock feedthrough. This phenomenon induces an error on the output signal value. In order to cancel the clock feedthrough effect, we use a new method based on a current feedback loop. The circuit is designed in 0.8 μm AMS “Austria Mikro Systems” single poly CMOS process. Measurements of the modulator are performed under A/D converters characterisation system, and show 55 dB dynamic range at 2.048 MHz sampling rate with 8 kHz input frequency bandwidth. These characteristics are suitable for audio applications.

[1]  H. Traff,et al.  Novel approach to high speed CMOS current comparators , 1992 .

[2]  Mourad Loulou,et al.  A 3.3 V switched-current second order sigma-delta modulator for audio applications , 2000, 2000 IEEE International Symposium on Circuits and Systems. Emerging Technologies for the 21st Century. Proceedings (IEEE Cat No.00CH36353).

[3]  Mahesh B. Patil,et al.  Measurement and analysis of charge injection in MOS analog switches , 1987 .

[4]  P. Roux,et al.  Charge injection error reduction circuit for switched-current systems , 1997 .

[5]  Hyeong-Woo Cha,et al.  A Clock-Feedthrough and Offset Compensated Fully-Differential Switched-Current Circuit , 1995 .

[6]  Eric A. Vittoz,et al.  Charge injection in analog MOS switches , 1987 .

[7]  John B. Hughes,et al.  Switched-currents : an analogue technique for digital technology , 1993 .

[8]  Nianxiong Tan,et al.  A fully differential switched-current delta-sigma modulator using a single 3.3-V power-supply voltage , 1994, Proceedings of IEEE International Symposium on Circuits and Systems - ISCAS '94.

[9]  John B. Hughes,et al.  Second generation switched-current signal processing , 1990, IEEE International Symposium on Circuits and Systems.

[10]  Gabor C. Temes,et al.  Oversampling delta-sigma data converters : theory, design, and simulation , 1992 .

[11]  Mourad Loulou,et al.  A 3 V second order sigma delta modulator using a pseudo bilinear switched current integrator , 1996, 1996 IEEE-CAS Region 8 Workshop on Analog and Mixed IC Design. Proceedings.

[12]  Christofer Toumazou,et al.  Analogue IC design : the current-mode approach , 1993 .