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ADC128D818 ADC clock and EMI

Mark Guastaferro
Genius 11645 points
Other Parts Discussed in Thread: ADC128D818

In troubleshooting system EMI issues, a large emmision around 196 MHz is noted from the ADC128D818. This can be seen at initial power up without any specific data transmissions. The device is in default power up mode, which it is assumed the ADC is not sampling. 

There is no informaiton in the data sheet about the internal clocks.Could this 196 MHz issue be from the internal ADC clocks?  Is there any way to reduce EMI emmissions?  

  • 0
    TI__Genius 16890 points
    Hi Mark,

    It starts up with the START bit = 0 so it is not doing any conversions. It does a reset when powered on which puts the default values into the registers.

    There is an internal clock that is running at about 360kHz.

    Does the EMI emission ever stop or is it continuous? If they remove the ADC128D181 and start the system what do they see? (The system may not start properly but is the emission still there?)

    When they start the part converting is the emission still there?

    Mike