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    ADC input with low pass RC filter

    I’m trying to implement 8 bit ADC in FPGA. FPGA running at 100MHz clock. PWM signal is given to RC filter. Knowing that f=1/2piRC, I have trouble with choosing the component's value. Is there any rule to find RC values and frequency?

    I chose 100Mhz frequency, 7Kohm resistor and 10nF capacitor. I didn’t‘t get expected output. I used LVDS buffer of FPGA as comparator. Considering the LVDS behavior, How to find resistor value?

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    Re: ADC input with low pass RC filter

    Hi,

    We don´t know about your circuit.
    We don´t know what kind of ADC you try to build.
    We don´t know what cutoff frequency you like to have.

    I chose 100Mhz frequency, 7Kohm resistor and 10nF capacitor.
    No.
    If you solve the above equation with "7kOhms" and "10nF" then the result "f" = 2.27kHz ... this is far away from 100MHz.
    What do you try to achieve?

    I didn’t‘t get expected output.
    What output did you expect?

    Klaus
    Please don´t contact me via PM, because there is no time to respond to them. No friend requests. Thank you.



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  3. #3
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    Re: ADC input with low pass RC filter

    You say ADC and then you mention PWM, which is DAC.
    Which are you really trying to do?

    It it's PWM DAC, what is the highest modulation frequency of the PWM?
    Zapper
    Curmudgeon Elektroniker



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