Energy Efficiency of Multi-bit delta-sigma Modulators Using Inverter-based Integrators

Energy efficiency of multi-bit ΔΣ modulators has been investigated in terms of a normalized power dissipation, which is commonly referred to as the figure-of-merit (FOM). The multi-bit modulators are designed by adding a multi-level comparator and feedback path to a conventional inverter-based modulator. The FOM is estimated by transistor-level circuit simulation assuming a 0.18-μm standard CMOS technology. In the present 3-bit modulator, the FOM is improved by more than a factor of two compared with a conventional 1-bit one. By using the multi-level comparator, the smaller quantization error reduces the settling time in the integrators, and then improves the energy efficiency.