Kam Chuen Wan

A RE-CONFIGURABLE ARCHITECTURE FOR SWITCHED CAPACITOR SIGMA-DELTA ANALOG-TO-DIGITAL CONVERSION

A re-configurable switched capacitor sigma-delta analog-to-digital conversion architecture1,2 is proposed. The architecture consists of a MASH sigma delta modulator with nth lower-order (first- or second-order) loops cascaded together. Each loop can be powered on or off operating in high or low performance mode, according to application needs. The architecture can be configured to optimize performance and power consumption for specific resolution and applications. The architecture is proven by means of a prototype, implemented as a fourth-order and fabricated in a standard 0.18 um CMOS technology. The outputs of both high performance mode (fourth-order) and medium performance mode (second-order, first loop ON) are measured to demonstrate the configurability. The FFT demonstrates that the noise shaping for the fourth-order modulator is better than that of the second-order modulator with steeper noise shaping slope.

A re-configurable 4 th order switched capacitor ΣΔADC for adjusting power and performance

A re-configurable MASH ΣΔ ADC is implemented in 0.18μm CMOS process. The proposed technique configures the ADC architecture for optimal power for specific resolution and applications. For high performance applications, the first integrator stage of the cascaded modulator may be constructed from larger transistors and capacitors to reduce thermal and op amp noise. However, this larger first stage also consumes more power than later stages constructed from smaller transistors and capacitors. Thus the first stage tends to provide a higher resolution while consuming more power than later stages, which have lower performance and lower power consumption. The principal advantage of this architecture is that the ADC is adaptable for applications with different performance and power consumption requirements. Although the ADC was designed for audio applications, this re-configurability is also useful for multimode communication systems.