Modeling of a 200 KHz Bandwidth Low-pass Switch-capacitor Sigma-delta DAC with a Raised Spur-free Modulator

This paper proposes a modulator that improves the signal-to-noise and distortion ratio (SNDR) by 6 dB compared with the conventional modulator. A high pass dither shaper added to the raised modulator eliminates harmonic spurs without increasing the in-band noise floor. Moreover, a behavior-level modeling method is proposed for a 200 KHz bandwidth switch-capacitor sigma-delta digital to analog converter (SC ΣΔDAC). Consequently, by considering the main non-idealities in the SC ΣΔDAC, in contrast with the conventional SC ΣΔDAC, MATLAB simulation results show that the SC ΣΔDAC with the proposed modulator boosts the SNDR by approximately 6 dB and the spurious free dynamic range (SFDR) by approximately 8 dB. Finally, with the circuit implemented in a 0.18 µm CMOS process, the measurement results are also used to further validate the proposed SC ΣΔDAC model.