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AD9625 high distortion

Question asked by thotho on Apr 22, 2016
Latest reply on Apr 25, 2016 by JudyChui


I use an AD9625-2.0EBZ evaluation board to test an AD9625 and I use a Virtex 6 to acquire the dates.

I set the clock frequency at 2GHz and I use the configuration 6 lanes, 1 octects/frame.

When I calculate the ENOB with an Input signal at 20 - 30 MHz the value is 9.1 bits, but at higher frequencies (>50MHz) the value is 6 - 7 bits.

The datasheet reports a value of 9.3 bits untill 500MHz.

The SNR that I find is coincident with the value reports on the datasheet, but with high input frequency I have distortion due at the second and third harmonics.

Can it be due at the evaluetion board? I don't think that I mistake to acquire the dates, because at low frequency the value of enob is correct, and when I bypass the ADC configuring tha SPI to obtain a ramp in output I obtain all value.

Can you help me?