AD9822 noise

Hi

I am designing an ADC circuit for CCD, I am used ADC9822 and the circuit is exactly same as datasheet.

The sampling rate is 1.25MHz and ADC is programmed in single channel and CDS mode. The noise at the output is too much and I am losing 7 bits of the digital value. The attached file shows the digital output of the AD9822 while the analogue input is grounded.

Could you please help me to reduce the noise level in the output?

Also I need to mention that ARM cortex4 is used to generate required signals for ADC.

Thanks

Parents
  • Majid,

      Take 2V FS and divide by 2^14.  That's an LSB.

    For a 14 bit system, I would start with a four layer board with a full layer for a ground plane.

    Switch to a lower noise reg:  ADM7150

    Repeating:

    " It's probably not the part, but rather bypassing or pc board layout.  How many layers is your pc board? 

    Schematic?  Noise on power rails?"

    Harry

Reply
  • Majid,

      Take 2V FS and divide by 2^14.  That's an LSB.

    For a 14 bit system, I would start with a four layer board with a full layer for a ground plane.

    Switch to a lower noise reg:  ADM7150

    Repeating:

    " It's probably not the part, but rather bypassing or pc board layout.  How many layers is your pc board? 

    Schematic?  Noise on power rails?"

    Harry

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