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IEC60730 - ADC values misreading

SangHyuk Jung
Prodigy 40 points
Other Parts Discussed in Thread: TMS320F28062

Dear,

currently, our product has checked IEC60730 routine.

BUT,INTERMITTENTLY, DSP makes an error at checking IEC60730 - ADC part.

DSP has missread ADC value(about more "200").      (HW is connected at GND.)

i knew if ADC results is out of range(-150 ~ 200), It is FAIL!!!!!!.

normally, ADC result values is 0 ~ 10.

but when we change ADC clock from cpu clock /2 to cpu clock /4,

This situation has not occurred for  > 20000 times. <- experimental results

detail setting parameter is below.

------------------------------------------------------------------------------------

SysCtrlRegs.PCLKCR0.bit.ADCENCLK = 1;

AdcRegs.ADCCTL2.bit.CLKDIV2EN = 1;

                  ~

 testAdcObject.pinACount = 0;
 testAdcObject.pinBCount = 0;
 testAdcObject.useInternalInput = 0;
 testAdcObject.muxChannel = 7;
 testAdcObject.singleChannelSelect = 0;
 testAdcObject.delayCount = 500;

 pTestAdc = (STL_TYPE3_ADC_TEST_adcTest_Handle)&testAdcObject;

------------------------------------------------------------------------------------

i want to know why this situation has occurred INTERMITTENTLY.

THANK YOU!

_Hyuki

  • 0
    TI__Genius 16281 points

    Hyuki,

    Which C2000 device are you using?  Is your HW TI control card or custom HW?

    regards,

    Joe

  • 0 in reply to Joe Prushing
    Prodigy 40 points

    Hello Joe,

    I have used TMS320F28062 & board designed by company.

    Regards,

    _hyuki

  • 0 in reply to SangHyuk Jung
    TI__Guru* 81560 points

    Hyuki,

    Can you give more information on the fail mode; is this happening all the time on a "bad" device or only ever so ofter on a given(or all ) devices.

    Only think I can say on increasing the clock divider to /4 is that it would make the S/H longer and help filter out any noise that may be in the system better than /2.


    Matt

  • 0 in reply to SangHyuk Jung
    TI__Guru 62975 points

    Hyuki,

    A few additional questions.

    1. Are you using the internal zero-pin oscillator as the device clock source or an external clock source like a crystal?
    2. What is the device frequency?
    3. When you sample ground, are you using a physical ADC pin to ground or the internal B5 ground path?
    4. Do you have split ground planes between Digital GND and Analog GND?
    5. Are you using internal or external reference for ADC?

    -Tommy

  • 0 in reply to MatthewPate
    Prodigy 40 points

    Dear Matt,

    Thanks for your interest.

    first one, we produced about more 20000 products and have produced that.

    recently, this phenomenon occur only one.

    and i checked this product is normal.

    Second one, i agree with your opinion.

    changing ADC clock from /2 to /4 have the same as the S/H is longer(2 times).

    so this makes ADC proccessing be more reliable, i think.

    MORE,

    i found out solution at ERRATA(Ver.H) - ADC initail conversion.

    Intermittently, ADC result have the false value.

    so we revised this point and then we can not copy this problem.

    If you are interested about this issue, please refer 28062 ERRATA(Ver.H)-ADC initial conversion section.

    Thanks and regards,

    Hyuki.

  • 0 in reply to tlee
    Prodigy 40 points

    Dear Tommy,

    Thanks for your interest.

    Please refer below answer.

    A few additional questions.

    1. Are you using the internal zero-pin oscillator as the device clock source or an external clock source like a crystal?

    I am using an external clock source(crystal)

    1. What is the device frequency?

    20MHz

    1. When you sample ground, are you using a physical ADC pin to ground or the internal B5 ground path?

    Physical ADC pin to ground.

    1. Do you have split ground planes between Digital GND and Analog GND?

    OF COURSE.

    1. Are you using internal or external reference for ADC?

    External reference

     

     

    recently, i find out solution at ERRATA(Ver.H) - ADC initail conversion.

    Intermittently, ADC result have the false value.

    so we revised this point and then we can not copy this problem.

    If you are interested about this issue, please refer 28062 ERRATA(Ver.H)-ADC initial conversion section.

    Thanks and regards,

    Hyuki.