MCP3551 - Single reference

[SpottedDick]

Hi,

I had a post on this already, but I had everything completely wrong and so muddied the waters and wanted to start again.

I'm looking to measure a 0-2.5V signal using an MCP3551.
MCP3551 Data sheet:
https://ww1.microchip.com/downloads/aemDocuments/documents/OTH/ProductDocuments/DataSheets/20001950F.pdf

Block diagram attached.

I'm trying to lower down the component count.

With a 0-2.5V signal, can I can tie both Vin- and Vref together to a 1.25V reference to get the full range?
VDD is 3V and VSS is 0V.

If understand the operation correctly, Vref is basically the swing voltage and Vin- is the "centre". So with this setup, I should get the full 22 bits from 0-2.5V. With 0-1.25V being negative and 1.25V to 2.5V being positive. Is this correct?

Just as a bonus question, I'm not sure how linear the output is going to be. For example, does the 0-1.25V range have 21 bits spread across it equally?

[magic]

I think you understand it right.

As for linearity, figures 2-1 to 2-3 appear to plot measurement error (in parts per million of full scale input range, 2·Vref) vs applied differential input voltage. Note that all INL specs apply to the case of common mode input voltage being Vref/2, but CMRR is typically 135dB so CM voltage shouldn't make a huge difference hopefully.