About BQ26220 Colomnb Counter mesurment characterstic , "Liner" or "Non Linear" ??

Hello

I have question about  Coulomb Counter  device BQ26220 .

This device has  Coulomb Counter Measure function by SENS  resister

between SRP and SRN.

This measurent by internal  A/D Converter for Resiter Voltage.

Of cource normal A/D Convert Voltage measurmet  is " Linear " line ,

But   this device Columb Counter  Measuarment result was diffrent,  

BQ26220 Colomb Counter measurment  was  " Non Linear  "  line by measurement  result.

Low Level was "Linear"  line and OK , but High Level is "Non Linear" line.  

We used this device for multi cell sysytem by Voltage devider and just use for Colomb Counter.,

Current range is  between  Small Current and High Current with both sens Resiter in System.

Question

1)  Dose  BQ26220 Colomb Counter measuremet characterstic  "Liner " line  ?  

2)  If  Colomnb Counter measurement characterstic  is " Non Liner "  line.  

   How to Calibration for this BQ26220 device Colomb Counter with A/D Conveter?

Couud you give me something advice?

Regard

Jasper