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DAC34H84EVM 5th-Order LPW Components

LeonardEllis
Guru 71516 points
Other Parts Discussed in Thread: DAC34H84EVM, DAC34H84

The schematic for the DAC34H84EVM shows a 5th-order LPF at each output.  Contained in this LPF are inductors and capacitors, as expected, but the caps are DNI and the inductors are 0-ohm resistors.  For example, D1/D2 output has L27, L28, L29 and L30 shown as inductors, BOM has them as 0-ohm resistors.  C251>C259 are DNI.

How and why are these to be installed, and how are the values determined?  Some of the caps are designated as 3.3pF, but not all.  I do not see any reference to these values or selection process in the EVM User Guide.

~Leonard

  

  • 0
    TI__Genius 9695 points

    Hi Leonard,

    The footprints have been provided so that customers can design and implement their own filters on the DAC34H84 EVM. The requirements for a filter will vary depending on the desired center frequency, passband and the output load and so it is not possible to select the components beforehand.

    Thanks,

    Eben.

  • 0 in reply to Ebenezer Dwobeng
    TI__Guru 71516 points

    Well, my appreciation to the EVM designer who had the forethought to provide for the possibility of filtering, even though the EVM does not need the filter.  This makes is so much easier and flexible for development and testing.

    ~L