TMS320F28377s: Sincfast Bandwidth in SFDM

Jacod,

Your question is not clear.

What do you mean by bandwidth? are you asking for relationship between samples rate of SDFM vs ENOB for SincFast filter? and also how did you get .26 number?

Regards,
Manoj

Hi Manoj,

The bandwidth of the filter would be the -3db point.  For a sinc3 filter this is .26 multiplied by the datarate.  

This is easy to calculate because sinc1/2/3 filters are well known functions.  I cannot find any information on the transfer function for the sincfast filter and hence am unable to calculate the bandwidth of the filter, I'm assuming that the sincfast filter has a similar relationship between datarate and filter bandwidth...

This TI Design helps to further elaborate.

Regards,

Jake

Jake,

You can find this information in SD-modulator DS.

Regards,

Manoj

Hi Manoj,

I have not found this information captured in the modulator datasheet.

The filter is implemented in the C2000 SFDM module. Most modular datasheets will call out results for the typical sinc1/2/3 filters but the sincfast filter seems to be something that is unique to the C2000 family.

Regards,
Jake

Jacob,

I'm not sure about this relationship.But, can you explain how you cameup with 0.26 number?

Regards,

Manoj

Hi Manoj,

The .26 is the ratio of the datarate to the -3db point of a sinc3 filter.  The sinc filter transfer function can be found in this app note.  

As the datarate of a sinc filter sets the first valley there's a nice correlation between the datarate and the -3db point. 

The SFDM module shows a graph of the frequency response vs filter.  It appears to be a modified sinc filter.  I just cant extrapolate the -3db point from the graph.

-Jake