AD7606C System Gain Calibration

Question

Hello, 
 I try to understand the AD7606C System Gain Calibration, but I have problems. I want to know what's resolution of gain error in LSB i can correct with the CHx_GAIN registers. 
 There is no clear description given in the datasheet, and I can make no sense out of Figure 93. "System Gain Calibration, with and Without Calibration", which I am not able to reproduce. When I try to calculate this myself, I get totally different values. 
 The FAQ mentions an application note ("A.N. 2011") that should explain further details, but that is nowhere to be found. 
 - Can you please give the formulas (Error (LSB) vs. Rfilter & Error (% of FSR vs. Rfilter)) that were used to calculate Figure.93? - Can you please share the mentioned application note? 
 It seems that each bit in CHx_GAIN can correct a gain error of 32 LSBs, but I want to be sure. 
 Regards, rehfi

Lluis · Accepted Answer

Hi rehfi, 
 The A.N. 2011 is the pdf posted in first link: (+) What are the benefits of Software mode compared to Hardware mode or AD7606 - Documents - Precision ADCs - EngineerZone (analog.com) , but it was never released to the webpage. will follow up. 
 -Fig 8. You are right, the larger the R_in, the lower impact an Rfilter has on the gain error. 
 -Fig. 14. You're right. Depends on whether you express it as a function or FS or FSR you divide by 2^25 or 2^16. 
 -Fig 15. You are refering to the left y-axis on tha a) figure? wondering if I mixed up AD7606C-18 and AD7606-16 plots? i.e. divided by 2^17 instead of 2^18. I could look find the code I used to plot this data, thanks for the spot. 
 Regards, 
 Lluis.)