Hi,

I have a question related to a delta sigma modulator. What does determine the full scale of a delta sigma modulator. Is it the reference voltage of the quantizer or it is the reference voltage of the feedback DAC in the delta sigma modulator. For example if the supply voltage of the modulator was 1.8-V and the reference voltage of the DAC is 1.5V, would that mean the full scale of the modulator is 1.5-V?

If my supply voltage is 1.8-V, how should I set the reference voltage of the quantizer and the reference voltage of the feedback DAC to be able to apply an pseudo differential input of 1.8-V?




I am a bit confused and it will be highly appreciated if someone elaborate it.

Thanks Tako.

So, if I'v understood correctly,

1- for a single-ended delta sigma, if we want to have an input full scale of e.g. VFS we need to set the reference voltage of the feedback DAC to two times of the VFS (i.e. Vrefn=0 and Vrefp= 2*VFS)

For a fully differential delta sigma, if want to have an input full scale of VFS, we need to set the reference voltage of the DAC to VFS (i.e. Vrefn=0 and Vrefp=VFS).

Am I right?