2 Replies Latest reply on May 21, 2010 10:57 AM by manuel.julian.moron

    DAC6

    manuel.julian.moron

      I input a 6bits_code_min=0dec or 6b_code_max=62dec value into the DAC6 by means WriteStall API and I get unexpected Voutput value.

         

      Theoretically the DAC6 datasheets told us:

         

      Vout=(Vrefhi-AGND)*ACap/FCap+AGND

         

      Taking into account my reference Vdd/2+/-BandGap I must to have:

         

      Vout(max)=3.76V

         

      Vout(min)=2.5V

         

      Instead of this I obtain a more or less a  Vout=3.7 V  and after that the value is going down until reach

         

      aproximattely 2.5V. I put the analog outputs in High Z.

         

      The C code is simple:

         

       

         

       

         

      #include

             

       

         

      "PSoCAPI.h" // PSoC API definitions for all User Modules

         

       

         

       

         

      #define

          DAC_MAX (    62    )     // Define max DAC value as 62    

       

         

      unsigned

              char    bDACValue = DAC_MAX;     // Variable for the DAC value    

      unsigned

              char    j;     // Variable for an index    

      int

       

          i;   

      void

      {

      DAC6_Start(DAC6_HIGHPOWER);

          main()     // Start DAC6 in HIGH power mode    

      BUFFER_Start(BUFFER_HIGHPOWER);

       

          while    (    1    )     // Repeat forever    

      {

       

          //for(j=0; j<62; j++){    

      DAC6_WriteStall(bDACValue);

       

      for(i = 0xFF; i != 0; i--); // Delay loop

          for    (i =     0xFF    ; i !=     0    ; i--);     // Delay loop    

       

          for    (i =     0xFF    ; i !=     0    ; i--);     // Delay loop   

       

         

      }/*while*/ /*main*/

         

      Anyone could tell me what's going on?  Thanks

         

       

         

      }

        • 1. Re: DAC6
          graa

          Some points to check:

             

          1. What is the column clock setting for the DAC?  Depending on the power you operate, there is a maximum column clock limitation.  If the column clock is more than the limit, then the DAC output will not be as expected.

             

          2. Is the DAC set to signed or unsigned?  If set to unsigned, you will get REFLO at the output, ie, 1.3V.  For a value of 62, you should get REFHI which is 3.8V

          • 2. Re: DAC6
            manuel.julian.moron

            I'm using a 136KHz frecuency column clock. Much lower than the 3.2MHz  let it with high Power

               

            use modele way.

               

            The DAC is signed?

               

            The input data is OffsetBinary. I shoudl to obtain following the formula a values between 2,6V and 3,9V.

               

            I got a ramp, but is not between the values I hope.