3 Replies Latest reply on Jan 18, 2018 2:19 AM by vsrs

# Effective resolution and Voltage Range DelSig ADC PSOC3

Hi folks,

considering setup of PSoC3/DelSig i was wondering, if how to interpret voltage range setup vs. effective resolution.

Assume neg. input of ADC is put on ground and Vref is setup external along with 1.024V generated externally. Additionally selected Level Shifted buffer mode, resolution 20Bit.

If I went to setup range as follows:

Which voltage range is to be choosen for calculation of resolution??

Case 1:

(Vref*2)/2^20

Comment:

• Does it mean, an Offset has to be added to result provided by DelSig, as we're not able to get values <-100mV but range has been setup as defined above?

Case 2:

(abs(-100mV)+Vref)/2^10

Comment:

• abs(-100mV) is minimum possible voltage for ADC

Case 3:

Choosing Rail to Rail buffer mode actually expecting this:(Vref-100mV)/2^10

I'm a little bit confused, thanks for  your efforts in advance!

Joe

• ###### 1. Re: Effective resolution and Voltage Range DelSig ADC PSOC3

Pls. note, ADC input is setup differential.

• ###### 2. Re: Effective resolution and Voltage Range DelSig ADC PSOC3

What if i do change input range of DelSigma?Let's say -inputADC +/- Vref/2. How does this affect resolution, as gain is achieved by switching capacitor in DelSig and not by OpAmp/Buffer in front of DelSig

Case 1:

(Vref/2*2)/2^20

Comment:

Is this true?

• ###### 3. Re: Effective resolution and Voltage Range DelSig ADC PSOC3

Hi,

As you have specified (Vref*2)/2^20 will be the range. The range which is related to the buffer is not depending on the resolution but rather affects the range of the individual pins.

So the voltage on the individual pins can vary  according to the image on the right side. But at the end it should be within the differential range shown on the left side. For range calculation value specified on the left alone should be used. hope

I hope this clarifies your doubt.

Best Regards,
VSRS