Figure 4—The DAC value and R_SET are used to set the current (I) in forumla a. Formula b shows how REF_HIGH and REF_LOW set the range between V_HIGH and V_LOW. Formula c sets a limit to V_OUT so the current source operates linearly. Formula d is obtained after substituting all of the above in Equation 1. Rearranging, you arrive at e, where adjustable and measured parameters are on the left and system parameters are on the right. Use f to internally calibrate V_REF by using ADCINT12.