LTC2400 output is 2x larger...

Discussion in 'General Electronics Chat' started by dtvonly, Mar 2, 2014.

  1. dtvonly

    Thread Starter Member

    Dec 14, 2012
    43
    0
    Hi I am putting together a "duplicate" test box. However, the output of the second box is twice as large as the first box. I had measured the input into to LTC2400 and both are the same. However, the 24-bits data that my PIC18F24k22 clocked in resulted in an ADC value that is twice as much as the first box. I had not checked to clock signals from the second box but the clock should not matter. If for some reasons the new hardware changes the clock to the LTC2400, the ADC result would be done faster (or slower), but not be twice as big. I am using two IOs from the PIC18F24k22. One IO as a data input from the LTC2400, and the other IO serves as a clock bit to the LTC2400. Please advise. Thank you.
     
  2. MrChips

    Moderator

    Oct 2, 2009
    12,451
    3,370
    Did you check the reference voltage on pin 2?
    If the reference voltage is lowered, the digitized value will be higher.
     
  3. dtvonly

    Thread Starter Member

    Dec 14, 2012
    43
    0
    Hi. Vcc=5 and Vref (at pin 2) = 5V (from a precision voltage IC - LT1236BIS8). What else can I check? Thank you.
     
  4. MrChips

    Moderator

    Oct 2, 2009
    12,451
    3,370
    What is your clock frequency?

    Also check your synchronization with the data stream. If your data is shifted by one bit it will change the value by a factor of two.
     
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