Ramp generation through HSMC DAC Stratix III using DSP Builder

[Altera_Forum]

I am able to generate proper ramp signal in DSP Builder simulink but when I program it into the FPGA, the output signal through the HSMC DAC is saturating. What is causing this and how to remove this saturation??

[Altera_Forum]

Is there an output transformer on the DAC? Have you checked that you are trying to output a signal within the bandwidth of any filtering on the DAC output?

[Altera_Forum]

--- Quote Start ---  Is there an output transformer on the DAC? Have you checked that you are trying to output a signal within the bandwidth of any filtering on the DAC output?  --- Quote End ---    Yes a transformer is present. What do I need to check? Yes, the bandwidth is within the range.

[Altera_Forum]

What you may be seeing is the effect of that transformer - assuming you are using the Terasic ADA board, I used that in a project at Uni a couple of years ago and the transformer basically just distorted signals at both low frequencies and high frequencies. 

 Have you tried other waveforms and frequencies?

[Altera_Forum]

I am trying to generate 100 Hz ramp signal that is quite low for the board but even if I try the same for higher frequencies like 10 KHz it shows the same saturation although the generated frequency is correct.In case of sine wave of 10 kHz and higher, the output signal is perfect.

[Altera_Forum]

If low frequency is causing this, how can this be corrected? 

Thanks for your support.

[Altera_Forum]

Given that it is probably the transformer causing this, there is no way to correct it short of generating an arbitrary signal which is predistored so that when it goes through the transformer it distorts back into the correct signal. But I'm not entirely sure how you would go about calculating that.

[Altera_Forum]

I am using AD/DA data conversion card (DAC5672) with Stratix III EP3SL150 DSP development board to generate Ramp signal of 1 V p-p and frequency 100 Hz through DSP builder. Is it possible to generate this ramp signal of 100 Hz? Is there any other data conversion card which can support this generation?

[Altera_Forum]

i have the same problem, how did you solve it?

[Altera_Forum]

I tried for 10 kHz, the output did look like a ramp but actually that too was saturated. I could not get any solution for this. Using an analog ramp generator circuit is the only solution for now.