2 Replies Latest reply on Dec 14, 2013 5:58 PM by user_14586677

    +/- (6*Vref) in Delata Sigma ADC

    keerthi.gowda

       The range of the ADC will be (Negative Input)+/-(x*Vref).(x can be 1/2, 1/4, 1/8, 1/16, 1, 2 or 6)

         

      The Vref can vary between 0.9 to 1.3V. Because external reference can also be used.

         

       

         

      If we use the (Negative Input)+/-(2*Vref), and the reference voltage is 1V. Then the ADC range will be (Negative Input)+/-2V. So if I fix the negative input at 2V, I can get digital readings between 0-4V (2-2=0,2+2=4).

         

       

         

      So If I need to measure from 0-5V its not possible. 

         

      But if I go with the next range,(Negative Input)+/-(6*Vref), I can cover the full voltage swing.

         

       

         

      So if the Vref used is 0.9, the range will be   (Negative Input)+/-5.4V.

         

      If the Vref used is 1.2V, then the range will be  (Negative Input)+/-7.2V.

         

       

         

      You can fix the negative input at any voltage to get full swing.

         

      But the limitation is the Pin voltage and current levels.

         

      This has to be taken care. The pin voltage should not exceed 5.5V.

         

      And negative voltage should not be given to a PSoC pin. 

         

      So to measure the negative voltages, kindly go through the below blog,

         

      http://www.cypress.com/?rID=50815&cache=0

         
              
         
          Keerthi