Simulative Evaluation of SNR in Asynchronous Sigma-Delta ADC

Abstract

This paper shows the difference between the SNR level for classical synchronous analog-to-digital converters (ADC) and asynchronous Sigma-Delta analog-to-digital converters (ASD-ADC). Simulative evaluation shows that conversion quality for ASD-ADC is 2 bit worse than for classical synchronous ADCs. The reason of such difference is at first the nonlinearity of ASD-ADC sampling block (ASDM) and at second quantization noise bigger than in classical ADCs. The quantization noise is caused by the need of two independent pulse edges time position measurements. The SNR is evaluated for three stochastic models of input signals: Gauss, uniform, sinusoidal.