AD7177-2, Missing conversions

Hi,

I'm having a particularly weird issue where I'm not receiving half of the converted values. When streaming conversions, I will receive three (seemingly) consecutive conversions, and then three or four conversions disappear, and then I'll get another three seemingly consecutive conversions. 

I know I'm getting 3 and missing 3 (or 4) because I'm feeding a sine wave in the ADC ch0 input and plotting the converted values on my computer. Every 3 points, there's a jump. 

Does this seem like a familiar issue? Am I somehow not accounting for some cooldown period?

I'm currently operating the chip in:

Ch0 on (Ch1,2,3 are all off)

Continuous Conversion mode (Sync_en off, Err_en = 11)

10KSps

WL32

Default Setup0, Gain0, Offset0

Internal reference

IOCLK = 500Khz

Parents
  • 0
    •  Analog Employees 
    on May 31, 2018 4:30 AM

    Hi,

    May I know what is your input signal amplitude and frequency? May I know also how many data points you sample on your measurements? If you could share to me your digital interface or the data you measured from a specific input signal, it would be great. According to the nyquist theorem, the sampling rate must be at least twice the highest input frequency component. Please take note also that the part requires a settling time at the very first conversion so it has different Tsettle at the first conversion and then the succeeding conversion will occur at the selected ODR. Same thing can be applied to the number of samples, the minimum number of samples (conversions) needed to replicate the signal is at least twice the ratio of your ODR/input frequency since the part needs the filter settling time at the very first conversion. The AD7177 is intended for dc type application, when you tried to input a pure dc signal, are you experiencing the data jump?

    Thanks,

    Jellenie

Reply
  • 0
    •  Analog Employees 
    on May 31, 2018 4:30 AM

    Hi,

    May I know what is your input signal amplitude and frequency? May I know also how many data points you sample on your measurements? If you could share to me your digital interface or the data you measured from a specific input signal, it would be great. According to the nyquist theorem, the sampling rate must be at least twice the highest input frequency component. Please take note also that the part requires a settling time at the very first conversion so it has different Tsettle at the first conversion and then the succeeding conversion will occur at the selected ODR. Same thing can be applied to the number of samples, the minimum number of samples (conversions) needed to replicate the signal is at least twice the ratio of your ODR/input frequency since the part needs the filter settling time at the very first conversion. The AD7177 is intended for dc type application, when you tried to input a pure dc signal, are you experiencing the data jump?

    Thanks,

    Jellenie

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