ADC31JB68: Balun configuration to the Analog Input.

Hi Rodrigo,

You can certainly use the type of transformer shown above. As long as the transformer can cover the BW/insertion loss required for your application.

Regards,

Rob

Hi Rodrigo,

Baluns typically have more BW than a transformer. This is typically why we have moved to more balun frontend interface designs to the ADC's analog inputs over the years.

Regards,

Rob

Hi Rodrigo,

I wouldn't think of it as current vs. voltage mode on a transformer. These modes describe a power transformer in better terms...which is not our case.

In our case, we are simply passing RF signals from a single-ended configuration, typically from a signal generator to a differential configuration in order to interface with the ADC appropriately.

Hope that helps.

Regards,

Rob

Hi Rodrigo,

I would use a blocking cap (0.1uF or smaller) at both the primary input and secondary outputs for either a transformer or balun. Typically putting DC, unless there is a center tap available, can make the transformer or balun respond poorly.

The only advantage is a balun type construction typically yields more BW. As most ADCs have multi-GHz BW today, we have gradually moved from transformers to balun type constructions to interface with the ADCs analog inputs.

In either case, if you find a transformer or balun that you think might work for your application beside thinking about BW or insertion loss. Please keep the phase imbalance in mind as well. Poor phase imbalance response gives rise to even order distortion, HD2, because the two 180deg out of phase signals presented to the ADC manifest themselves this way and the output result is higher than normal HD2.

If you want to dig deeper into this please Google my name and the words "transformer and balun". I have written many papers on this subject.

Regards,

Rob