My adc chip has proper SNR, but SINAD is awfully low.

[pansoo]

I have designed and measured my own adc chip.

Also I have measured a commercial adc chip.

My chip shows very low ENOB because of high THD.

The difference between my chip and commercial chip is harmonics.

My chip also has proper SNR, but SINAD is awfully low.

Commercial chip has almost same SNR and SINAD.

Where come from this problem? design? layout? noise? matching? measurement?

How can I solve this problem?

 

[rambus_ddr]

maybe you can check your circuit to find harmonic distortion cause