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ADC3683: Can ADC3683 work with 100kHz input signals?

Marsh Cai
Intellectual 1675 points
Part Number: ADC3683

Hi teams,

My customer is using ADC3683 on their products. When they input high frequency signals (sine wave, 600mVpp@1Mhz, 10Mhz,), ADC3683 can work well, with THD about -80dB. However, when input an low frequency signal (100kHz, 60kHz), the THD is only -60dB, no matter on the EVM or their own board. And we confirmed that the signal source is good, the THD is about -100dB.

Can you help to comments about this? Does ADC3683 only work for high frequency signals?

The configuration of EVM is attached.

TKs & BRs

Marsh

  • 0
    TI__Mastermind 18185 points

    Hi Marsh,

    This device is capable for DC coupled applications so there should not be any issue from the ADC itself. For the EVM, the input balun (ADT1-6T+) passband lower limit is 30kHz, so a 100kHz input tone is not a problem as it is within the intended passband. Can you upload the configuration as mentioned so one of our experts can take a look at this? 

    Regards, Chase

  • 0 in reply to Chase W
    TI__Intellectual 1675 points

    ...

    Hi Chase,

    Can you share your @ti.com email address to me? I can not attach the pic here. 

  • 0 in reply to Marsh Cai
    TI__Intellectual 1675 points

    They haven't used the balun. They input the differential signal into the EVM via J1 and J3 directly.

    Currently, we are confused with the whole testing process. When using ADC3683 to measure 1MHz sine wave, the THD is about -85dB. When it comes to 100kHz sine wave(generated by APX555, which is the professional audio equipment, and the output signal can be measured by itself, and we can see the THD is about -100dB), the THD is -65dB. 

    From the very beginning, the balun was suspected, and then we input the signal directly to eliminate the influence of it. So, actually right now, the entire lane is very simple. APX555->cable->ADC3683. We don't know how to debug now. Can you kindly share some inputs? 

    Any tests are accepted.

  • 0 in reply to Marsh Cai
    TI__Mastermind 18185 points

    Hello Marsh,

    Can you ask that the customer provide us the captured data with the 100kHz tone applied as well as the data while the 1MHz is applied? Qty. 2 CSV format is preferred. This will help as we can import it into HSDC Pro to check if there is anything glaringly obvious.

    Also, as I mentioned in my email earlier today, we'll take a look to see if we find the same result when driven with our signal generators. I'm not familiar with the APX555 or its signal integrity. Based on the info provided, it may be possible that the source is not as clean at 100kHz as it is at 1MHz (which our in-lab test would rule out if we find similar performance degradation). We'll provide an update to you early next week. Thank you for being patient with us.

    Regards, Chase 

  • 0 in reply to Chase W
    TI__Mastermind 18185 points

    Closing this thread since we have moved to email instead.