Efficient Multibit Quantization in Continuous-Time $\Sigma \Delta$ Modulators

A drawback of continuous-time SigmaDelta modulators is their sensitivity to clock jitter. One way to counteract this is to use a multibit feedback loop which requires a (high resolution) multibit quantizer. However, every extra bit in the quantizer doubles its complexity, power consumption and capacitive load for the analog circuit that needs to drive the quantizer. In this paper a new concept for the quantization in sigma delta modulators is proposed. It allows to significantly reduce the required amount of comparators in the multibit quantizer. Three architectures that realize this new concept are presented and their implementation issues discussed. The architectures´ performance has been compared with a conventional modulator through computer simulations. Compared to the conventional modulator, the proposed architectures achieve the same performance, with much less comparators in the quantizer