This dissertation presents a low-power high-resolution delta-sigma ADC. Two new architectural design techniques are proposed to reduce the power dissipation of the ADC. Compared to the conventional active adder, the direct charge transfer (DCT) adder greatly saves power by keeping the feedback factor of the active adder unity. However, the inherent delay originated from the DCT adder will cause instability to the modulator and complex additional branches are usually needed to stabilize the loop. A simple and power-efficient technique is proposed to absorb the delay from the DCT adder and the instability issue is therefore solved. Another proposed low-power design technique is to feed differentiated inverted quantization noise to the input of the last integrator. The modulator noise-shaping order with this proposed technique is effectively increased from two to three without adding additional active elements.
The delta-sigma ADC with the proposed architectural design techniques has been implemented in transistor-level and fabricated in 0.18 µm CMOS technology. Measurement results showed a SNDR of 99.3 dB, a DR of 101.3 dB and a SFDR of 112 dB over 20 kHz signal bandwidth, resulting in a very low figure-of-merit (FoM) in its application category. Finally, two new circuit ideas, low-power parasitic-insensitive switched-capacitor integrator for delta-sigma ADCs and switched-resistor tuning technique for highly linear Gm-C filter design are presented.