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ADS131M04: how we can achieve channel to channel Phase error & apply phase compensation

shraddha naik
Intellectual 290 points
Part Number: ADS131M04

Tool/software:

Hi,

I have gone through the datasheet for channel phase compensation.

If there is phase shift of 2.25 sample between 2 channel, we can create a shift of 2 sample channel1 wrt channel0, and 0.25 we can adjust using phase calibration function. In this case calibration function is same as configuring the PHASEn[9:0] bits in the CHn_CFG register?

In order to compensate any channel phase error, we need to find the the Sample Period offset between two channel. How we can find this sample period offset?

And if Sample period offset is 0.25 sample, how to get bit pattern of  PHASEn[9:0] BITS?

Regards,

shraddha

  • 0
    TI__Guru 52146 points

    Hi shraddha naik,

    The datasheet description lists the phase calibration settings and the range for each OSR - I have copied this below

    So if your OSR = 2048 then the phase offset range is -OSR/2 to +OSR/2 (or effectively +/-1/2 a sample period). This corresponds to a decimal value range from -512d to +511d. Therefore, you would program an approximate value of +/-256d to phase shift by 1/4 sampling period.

    You should be able to calculate the time difference between two signals by actually measuring them. You can use something like zero cross detection to determine the phase difference, then use the phase adjustment register to help correct for this

    -Bryan

  • 0 in reply to Bryan Lizon86
    Intellectual 290 points

    Hi Bryan,

    I understood that based on OSR, i can keep Phase offset value within the range it is mentioned.

    But what i need is how i can find the phase difference error based on the time difference between two signals?

    Also, once you get the time difference or phase difference between two signal, how i will know what phase offset value to be selected for respective OSR? For example I kept OSR is 256, So i can set -128 to +127, but between this range what value i need to keep? Can you give me example?

    Regards

    Shraddha

  • 0 in reply to shraddha naik
    TI__Guru 52146 points

    Hi shraddha naik,

    I included an example in my last post about how to convert the phase offset range for a specific OSR to 1/4 sampling period

    shraddha naik said:
    But what i need is how i can find the phase difference error based on the time difference between two signals?

    Yes I understand this, I also mentioned zero cross detection in my last post, and how you would use the difference between the zero crossings of two signals t determine their phase difference. Did you not read my post?

    -Bryan