Sigma-delta analog-to-digital converter

摘要

The present invention is related to a sigma-delta analog-to-digital converter (ADC). It further relates to a method for designing and manufacturing a sigma-delta ADC, and to a digital control loop comprising the same. According to the present invention, part of the filtering function required for noise-shaping is implemented in the feedback path. By suitably distributing the poles over the forward and feedback paths, stable operation can be achieved while offering low latency.

主权项

1. A sigma-delta analog-to-digital converter (ADC), comprising:
a first forward path connected to an input of the sigma-delta ADC comprising a filtering stage and a quantization stage, the first forward path having a transfer function Hff; a first feedback path from an output of the first forward path to the input of the sigma-delta ADC, said first feedback path comprising a digital-to-analog converter (DAC) and a digital filter for converting the output of the first forward path, said first feedback path having a transfer function Hfb; wherein the sigma-delta ADC has a stable noise transfer function NTF given by:NTF=11+Hff⁢Hfb=11+Hwherein H is the loop transfer function, said NTF having at least one damped zero;
wherein, if H comprises undamped poles, Hff comprising all the undamped poles of H, and wherein Hfb comprises at least one damped pole associated with one of said at least one damped zero; wherein the first feedback path comprises a finite impulse response (FIR) digital filter that has an impulse response that approximates the impulse response associated with Hfb, wherein the first N coefficients of the impulse response are implemented as said FIR filter, wherein N is at least equal to the time constant of the most low frequent pole of Hfb; wherein the FIR digital filter is combined with the DAC for forming a finite impulse response digital-to-analog converter FIRDAC.