AD7949 SDO error

Hi,

I have one problem with AD7949.

Please refer the attached.

Regarding SDO_NG sheet, after Power up, I have control in accordance with a sequence that is specified on the datasheet, but SDO does not go out. It works the same even after the 4th cycle. I believe that he period of tCYC is longer than the specification, and tCONV is more than 2.2uS. 

On the other hand, regarding SDO_OK sheet, I changed only tCONV from 3.3msec to 1sec. So It works correctly.

Can I ask you to give me the hint to solve this problem?

Are there any constraints such as settling time?

If you have any question, please let me know.

Best Regards,

yk

AD7949_SDO.xls