AD_Converter

Description

Simple analog to digital converter with a variable resolution of n bits. It converts the input voltage ppin.v-npin.v to an n-vector of type Logic (9-valued logic according to IEEE 1164 STD_ULOGIC). The input resistance between positive and negative pin is determined by Rin. Further effects (like input capacities) have to be modeled outside the converter, since this should be a general model.

The input signal range (VRefLo,VRefHi) is divided into 2^n-1 equally spaced stages of length Vlsb:=(VRefHi-VRefLo)/(2^n-1). The output signal is the binary code of k as long as the input voltage takes values in the k-th stage, namely in the range from Vlsb*(k-0.5) to m*(k+0.5). This is called mid-tread operation. Additionally the output can only change its value if the trigger signal trig of type Logic changes to '1' (forced or weak).

The output vector is a 'little-endian'. i.e., that the first bit y[1] is the least significant one (LSB).

This is an abstract model of an ADC. Therefore, it can not cover the dynamic behaviour of the converter. Hence the output will change instantaneously when the trigger signal rises.