LTC2323 Simulation in LTspice


I'm trying to simulate the ADC-LTC2323 16bit in LTspice in order to measure THD value of this converter and compare it with the datasheet. The model of the LTC2323 is available in LTspice. I'm connecting two sine signals to the differential inputs "ain-" and "ain+" of the ADC and then calculating THD with ".four " directive. The problem is that i'm getting too small THD values compared to those in the datasheet (ex: at fin=2MHz THD=4.5%=-26.9 dB, where according to the datasheet the THD should be -86.8dB at fin=2MHz). Is there something wrong with the model or my simulation isn't correct ??. Can anyone help??

Thanks in advance.

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    •  Analog Employees 
    on Sep 5, 2019 2:23 PM in reply to Niels

    I do not think you get enough points per waveform to get good THD results with a 2MHz sine wave and 5MHz sample rate. I tried slowing the sine wave down to 10kHz and got a THD of -92dB. 

    The other thing you could try is to set the sample size, sample rate and sine wave frequencies so that you get hits in all the bins and then shuffle the samples so that a single cycle of the sine wave is created and then calculate the fft.