ADC LTC2387-18 SNR test condition

Hi,

For the source, I suggest using the high-performance, low distortion Audio Precision audio analyzer. Preferably the AP2700 series.

About the filters, I'll contact the product owner and get back to you.

Regards,

Andrei 

Hi Andrei 
Thank you very much for your reply!
I have one more question,The Audio Precision audio analyzer can only generate sinusoidal signals below 204kHz.But the data sheet shows the SNR test results at 1MHz、5MHz or higher frequency points. To test the signal to noise ratio at higher frequencies, which signal source should be selected? 

Thanks again!

MYB,

Typically for signals at those frequencies you will need to use a signal generator with low native distortion and then follow that with a high quality filter around the frequency of interest.  The characteristics of the filter are that it needs to have a sharp cutoff such that the 2nd harmonic is attenuated to the extent possible and if possible a differential filter in this case would be nice.   Otherwise you can use a single-ended filter and follow the source with a low noise single-ended to differential conversion stage. 

Sean

This post does not say the specific instrument manufacturer or model. The maximum of AP instrument is 204khz. When fin = 1MHz, 5MHz, what manufacturer's instrument does your company use for manual parameter evaluation (fin = 2KHz, 1MHz, 5MHz)?

Hi @skowalik

In any case, can you or someone from the team can recommended specific instrument that we used to test this?

Thanks,

Jellenie

wxc5678, MYB,

I'm not sure what the specific instrument used for this data collection was as this product was developed in our California offices, but perhaps would be able to specify.  The key is to find a source which has low distortion to begin with such as a Rhode & Schwartz SMA100A/B.  

Sean

Use a low jitter high quality RF generator such as HP8640B. I know it is old but that is what I use. The output is fed through a multipole low distortion LC filter. (I use TTE Q70 1MHz for this.)Then you have to convert from single ended to differential with the proper CM voltage and the output of the differential signal is fed through a 3rd order CLC filter. Single ended to differential is done using two ADA4899 one in inverting mode (Common mode voltage is placed on noninverting input.) and one in buffer mode. This signal is fed into two ADA4899 buffers with the 1MHz CLC filter on the output of each.

Hi, have you some recommendation or materials for the CLC filter on the output? I use demo board DC2622A with two ADA4899 buffers with the 1MHz CLC filter on the output of each. I want  modify filter to higher frequencies. I try different types of filters and always it was worse.

Thank you,

Martin

Take a look at the following articles. You should find them helpful.

How to Drive the LTC2387 (Part 1): Signal Applications to 5MHz that Require Low Inter-Modulation Distortion | Analog Devices

LTC2387 Drivers Part II: Drivers for Imaging | Analog Devices

LTC2387_drivers_part_IIId.pdf (analog.com)