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Original question:

ADC5140EVM-PDK: Analogue Mic and Digital MEMS Mic Data to Windows Laptop through USB together Possible?

ADC5140EVM-PDK: It is best to measure the noise floor with the differential inputs shorted together and AC coupled to GND.

user6547614
Intellectual 340 points
Part Number: ADC5140EVM-PDK

TA = 25°C, AVDD = 3.3 V, IOVDD = 3.3 V, fIN = 1-kHz sinusoidal signal, fS = 48 kHz, 32-bit audio data, BCLK = 256 × fS, TDM slave mode, PLL on (unless otherwise noted)

IN1 differential input selected and AC signal shorted to ground, DRE enabled (DRE_LVL = –36 dB, DRE_MAXGAIN = 24 dB), 2.5-kΩ input impedance selection.

It is best to measure the noise floor with the differential inputs shorted together and AC coupled to GND.

with this test condition,the snr value not achieve 120db,it's 110db,  

  • 0
    TI__Mastermind 23050 points

    Hi,

    I do not see in your data where you have measured the noise floor of the device. If the proper settings are followed then you should see datasheet performance. There are preset configurations in the GUI that you may try using.

    Also based on your images it looks like your data format on the AP may not be set up correctly. the full scale range of the ADC is 2Vrms differentially, and a -60.6dBV signal should correspond to a -66.6dBFS reading, suggesting that your data is shifted by one bit. 

    Best,

    Zak

  • 0 in reply to Zak Kaye
    Intellectual 340 points

    which your case is high level performance case?i test the snr with your measurement,differentially input analog signal,with Maximum undistorted input amplitude with TDM 32BIT,it's -0.87dbv ,the THD+N with <%1,so i think the base test SNR condition,and then i test with -60.87dbv the THD+N is -54dbv,so the SNR is 60+54=114db.. i test with one channel ...