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  • TI Thinks Resolved

ADS4129: How to calculate the filter's capacitance of the ADS4129's input

Prodigy 150 points

Replies: 5

Views: 41

Part Number: ADS4129

Hello!

How to calculate the filter's capacitance of the ADS4129's input!

Thanks

  • Guru 59435 points

    User,

    You should be able to figure this out using Figures 114 and 115 in the data sheet. These show the resistance value of Rin and the capacitance value of Cin over frequency.

    Regards,

    Jim

  • In reply to jim s:

    Hello!

    In the input frequency is 250 MHZ, the input capacitance is about 3.6 PF, the input resistance is about 500 Ω,Can you tell me the relationship between the capacitance of r-c-r and the maximum input frequency?

    Thanks

  • Guru 59435 points

    In reply to user5318419:

    User,

    The r-c-r is a 250MHz low pass filter. If your IF is going to be above this frequency, remove these parts from the EVM.

    Regards,

    Jim

  • In reply to jim s:

    Hello,

    I want to  set the frequency 50MHz ,How should I calculate?

    Thanks!

  • Guru 59435 points

    In reply to user5318419:

    Use a filter simulation tool and enter the values for the internal R and C from Figures 114 and 115 at 50MHz. This would be about 10KHz and 4pF.  

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