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Overflow in DAC Calibration

Question asked by amf on May 19, 2017
Latest reply on May 23, 2017 by mark.ramos

Hi,

   I have a question about the DAC calibration (in non-attenuator mode).  I found that there are overflows when you use large resistor values for RCAL and RTIA in adi_AFE_TiaChanCal() and adi_AFE_ExciteChanCalNoAtten(), so I fixed those.  However, is there also an assumption buried in adi_AFE_ExciteChanCalNoAtten() as far as a limit as to the *ratio* you can use for RCAL to RTIA?  

 

     I use RCAL = 3 Mohms and RTIA = 4 Mohms, so the ratio is 3/4.  This ratio gets used in a calculation for a delta value to use when determining the DAC offset correction factor and the value ends up too large to fit in the DAC_OFFSET_UNITY register, or perhaps I'm mis-understanding the documentation.  Can you please look at my attached screenshots and let me know what you think?  My DAC is unable to accurately apply 0.6V across the load resistor, so the calculated offset is wrong. 

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