AD9822 noise

Question

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

FormerMember · Accepted Answer

Majid, 
 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)

FormerMember · Answer

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

FormerMember · Answer

I think the only way you are going to get the noise under control is to go to a four layer board. 
 Harry

EZAdministrator · Answer

This question has been assumed as answered either offline via email or with a multi-part answer. This question has now been closed out. If you have an inquiry related to this topic please post a new question in the applicable product forum. Thank you, EZ Admin

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AD9822 noise