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ADL14020 wave problem

Other Parts Discussed in Thread: ADC14L020

Input signal is WAWE-1, WAVE-2 is signal amplifier and input to the ADC. WAVE-LCD is waveform acquisition software to draw, the waveform VIN + amplitude in the ADC for LCD display waveform is right of 0.5-2.5V; but, more than amplitude after the emergence of the red circle in the waveform of the problem

WVAE-1

WAVE-2

WAVE-LCD

Schematic

Hewei

hew@wonhere.cn

  • Hi Hewei,

    What is your question?

    I can see that the waveform appears to be clipping. In fact, it appears to be clipping very hard near GND and it is probably activating the ESD diodes on the ADC.

    Regards, Josh

  • My problem is red circle in the waveform(WAVE-LCD/AD_DATA1[13:0]), DATA to drawing is wrong

  • Hewei,

    If I understand you correctly, you are comparing the data output from the ADC and the waveform measured at the input to the ADC (with an osciloscope) and they do not match. It appears that the data at the output of the ADC has some strange transients at the edges of the clipping boundary. Please correct me if this is not correct.

    Here are some ideas for the cause of this inconsistency:

    - The bandwidth of the oscilloscope is not wide enough to view the glitches.

    - The hard clipping is causing these transients in the ADC core but the event is not observable from the ADC input.

    Your data capture plot does not provide very much information about the waveform at the output of the ADC. Can you please provide a data set (decimal values in a 14-bit range) so that I can understand the time and magnitude scale of these events.

    Thanks, Josh

  • WAVE-2 is the waveform measured at the input to the ADC(pin 2,with an osciloscope)

    WAVE-LCD is the waveform drawed at lcd for my acquisition data

    at "WAVE-2",i regulate my signal range in 0- 2.6v(adc14l020 manul noted),“WAVE-LCD” is display correct

    but "WAVE-2",i regulate my signal range over 0- 2.6v(about -0.7v- 7v),“WAVE-LCD” is display the wrong in red circle

    I don't know what effect the ADC acquisition data is on the input signal of the  beyond input voltage range.

    With what method to solve the problem.

  • Please provide a dataset for the WAVE-LCD because I cannot understand the axes scale and values of the data when looking at the picture.

    Based on the WAVE-2 picture, it appears that your signal is clipping very hard below ground and activating the internal ESD diodes. If this is the case, then you are operating the ADC in range that will have unexpected results and may damage the part. I recommend re-adjusting the gain and center bias of your signal at the ADC input so that the signal does not clip against GND.

    Regards, Josh

  • thanks,I have solved it with an external clamp diode.