4DSP Support Forum

Products => FMC Products => FMC150 => Topic started by: Willie Thompson on July 15, 2013, 03:32 PM

Title: FMC150 Bypass Filter & DAC Replica
Post by: Willie Thompson on July 15, 2013, 03:32 PM

We are interested in bypassing the DAC output filter to allow the use of the higher Nyquist images. Is this possible using the FMC150?  In the future, we would like immigrate to the FMC110.  I have already try to bypass the filter using the resistor pads, however we are not able to see the higher replicas that should be produced by the DAC.


DAC Rate = 491 MHz
Input Data = 245 MSPS; 20MHz Baseband signal
DAC Interpolation = 2x

Title: Re: FMC150 Bypass Filter & DAC Replica
Post by: ebarhorst on July 15, 2013, 06:57 PM

Hi,


It is indeed possible to bypass the DAC output filter, bit that is not something we allow customers to do by themselves without voiding warranty.
4DSP offers a specific order code for the filter bypass. You can contact your sales representative for updating your FMC150 to incorporate the filter bypass.


Best regards,
Erik

Title: Re: FMC150 Bypass Filter & DAC Replica
Post by: samberhan on July 15, 2013, 08:08 PM

that's not what the data sheet states. I wish that was made categorically clear so that all this calling today we wouldn't have had to do to get why we were not getting the image replicas showing up at at later frequencies. One last question, does that mean, this would be the case also for the FMC 110? (we were planning to buy that for our final implementation?)
Anyway, thanks at least for the clear up, we know that our premise is correct.

Title: Re: FMC150 Bypass Filter & DAC Replica
Post by: Willie Thompson on July 15, 2013, 09:27 PM

Just for clarification, the only option to bypass the filter is via modification by 4DSP.   In addition, is there is restriction for the FMC110.  As we stated, we are concern purchasing the FMC110.  Thank you.

Title: Re: FMC150 Bypass Filter & DAC Replica
Post by: ebarhorst on July 16, 2013, 07:12 AM

Hi,


most of our products are designed to not impose any limit on the output and input bandwidth and leave the filtering up to the user. On the FMC150 however the default implementation during assembly is with an output filter on the DAC. We mention in the data sheet that it can be bypassed easily.  But we cannot support this as a user changeable feature. It is an ordering option. I am sorry this note in the user manual has caused confusion and we will look at wording it differently.


For the FMC110 we do not have any filtering on the output.


Best regards,
Erik

Title: Re: FMC150 Bypass Filter & DAC Replica
Post by: Willie Thompson on July 16, 2013, 08:10 AM

Erik


Thank you for the clarification about the FMC110.  One last question, is there a reference design for the FMC110 for the KC705, similar to the FMC150?


WLT

Title: Re: FMC150 Bypass Filter & DAC Replica
Post by: ebarhorst on July 16, 2013, 09:57 AM

Hi Willie,


the FMC110 can be used on a KC705 but you do need an FMC700 to create a real HPC connector. The KC705 does not connect all the high pin count signals to the FPGA and 4DSP has developed an adapter that uses both the Low pincount and (semi)high pincount connector on the KC705 to create one real High pincount FMC site. Aditionally it adds a cooling fan.


http://www.4dsp.com/fmc700.php (http://www.4dsp.com/fmc110.php)


4DSP delivers a reference design for FMC110+FMC700 when used on the KC705


Best regards,
Erik