• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 21 subscribers
  • Views 558 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LMX2595: 100KHz offset performance improvements

Stephen Sturges
Intellectual 290 points
Part Number: LMX2595

is it possible to improve the 100KHz offset performance by making changes such as to the loop filter,  what would we be giving up in doing that?  On most plots the 100KHz 10-16 offset is not much better the 10K offset number.

Thanks

  • 0
    TI__Expert 8485 points
    Stephen,

    Often times we use loop filters that give a bandwidth around the 100kHz offset, so you'll see those areas bump up and get about the same level as 10kHz. The general way to change that (or at least to show the lowest level around 100kHz), you would extend the loop filter bandwidth as wide as possible. This will be either changing the loop filter component values to be designed for a higher bandwidth, or one convenient way is to program the device's charge pump current to a higher value (this also increases the loop filter bandwidth). The trade-off of increasing the bandwidth is that you have less filtering on some higher offset spurs and the bump will now be placed at higher offset where some applications would like the lowest phase noise levels.

    For most easiest way of seeing these effects you can download a simulator tool and easily design and see the plots when you tweak parameters:

    www.ti.com/.../PLLATINUMSIM-SW

    Regards,

    Brian Wang