1. bpkoja

    Thread Starter New Member

    Mar 14, 2008
    3
    0
    Hi everyone!

    I'm have trouble with strange ADC single conversion offset.. I have RF04EB with cc2510. When I set ADC for single 8-bit conversion with 3.3V reference voltage, I get different values from those I have measured with voltmeter. Val. around 0V and 3.3V are matching, but in between I notice offset that is not linear, and it is the largest in the middle of scope ( about 100 mV ?!).
     
  2. mrmeval

    Distinguished Member

    Jun 30, 2006
    833
    2
    Is that some sort of TI dev kit?
     
  3. scubasteve_911

    Senior Member

    Dec 27, 2007
    1,202
    1
    No ADC is perfect, but you shouldn't be seeing such a large difference. From the datasheet, the integral non-linearity error isn't specified for 9-bit operation(seems to only operate 7,9,10,12 bit resolution). It is specified for 12-bit operation with 13.3LSBs maximum.. Is this were the same spec for 9-bit operation, it would make sense to see that much offset, but I am guessing that it would be much lower.

    Two things to check, is your reference low output impedance? Secondly, how accurately rated is your volt meter?

    Steve
     
  4. bpkoja

    Thread Starter New Member

    Mar 14, 2008
    3
    0
    Thanks for answering Steve,

    Reference voltage is 3.3V at AVDD pin, regulated with LP2985. For measurements, I have used digital oscilloscope. I have tested it for all possible resolutions and the result is the same. Analog voltage that is applied for conversion is the same as used for reference, brought thru a 10k pot.
     
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