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DDC114: DDC114 Current calculation equation

Yunjing Wang1
Expert 3360 points
Part Number: DDC114

Hi team,

My customer is using DDC114 for PHOTODIODE SENSORS current, they use below equation to calculate the actual input current, but with this equation and same integration time, they will get different calculation result when they choose different FSR range, it should be same if the input current is not change.

C=Q/U=It/U, where U=4.096V, t is integration time, C is DDC114 internal selected CF.
Then we can get input current I = CU/t
If ReadVal is the voltage code we read from DDC114，resolution is 16bit, u is the actual analog voltage, then we have ReadVal/2^16 = u/4.096

Because u = It/C, then ReadVal/2^16 = It/C · 4.096
Finally we have I = (4.096·ReadVal·C)/(2^16·t) , Unit is (pF·V)/(us) = uA. Where t is integration time, C is DDC114 internal selected CF.

  1. Could you pls kindly check if they are using correct calculation equation? 
  2. Is there a reference equation for input current calculation? 
  3. Is there a reference C code for DDC114? 

Thank you!

Yunjing