Question

Hey everybody, 

A small question. I need to generate a signal of 28.8MHz (sine wave), so in FPGA I've build a DDS and it's generating a nice sine wave @ 27.799MHz (close enough :p). For connecting this to a certain target board I've bought the PMOD DA3 (https://store.digilentinc.com/pmod-da3-one-16-bit-d-a-output/). There is only one small problem that I can't figure out... 

I know when you're sampling you have to comply to Shannon's theory, but how is it with DACs when you are reconstructing a signal, do they also have to comply to this? I've dived into the schematic of the PMOD DA3 and saw that a chip from Analog Devices is used, more specific the AD5541A. When looking into the datasheet, I saw that it connects with a 50-MHz SPI-/QPSI-/... interface, meaning that SCLK can take a maximum of 50MHz when a voltage supply of 2.7 - 5.5V is applied...

Now the question that I have is, does a DAC need to comply to Shannon's theorem, meaning that the absolute max I can generate with this DAC is a 25MHz signal (in ideal conditions), or does a DAC not have to comply with this and I can just generate the signal without any problem :)?

Thank you :)!

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Hi @tommienator,

According to my basic understanding, if we increase the SCLK signal up to 50 MHz for Pmod DA3 module, the speed of the reconstruction  process will be higher .

Hence I believe DAC doesn't need to comply the Shannon's theory.

Regards.

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