CC1175 - can Frequency Synthesizer loop bandwidth be adjusted lower with external components?

Lance Carlson

Other Parts Discussed in Thread: CC1175, CC1070

CC1175 Frequency Synthesizer bandwidth can be adjusted over a modest range (101.6 - 170.8 KHz) via settings in the FS_DIG0 register according to the User's Guide.

I'm wondering if the bandwidth can be made even lower by changing external components? The datasheet mentions "external loop filter components" for the pins: LPF0 and LPF1, however the application circuit diagram and reference design have only a single capacitor connected between these pins, and neither the datasheet nor user's guide provide any guidance about alternate circuit topology which might be used to modify loop bandwidth.

Is any guidance available about alternate circuit topology or component values which could be used in conjunction with LPF0/LPF1 pins to modify (lower) the Frequency Synthesizer loop bandwidth? My application would benefit from much lower bandwidth.

Thanks!

over 11 years ago

0 TER over 11 years ago

TI__Guru**** 317180 points

To understand more:

Why do you want to reduce the loopfilter bandwidth?

0 Lance Carlson over 11 years ago in reply to TER

Prodigy 85 points

Hi,

I can't tell you exactly why I want to reduce loopfilter bandwidth on a public forum, sorry! If you need to know more details please send me an email directly, outside this forum.

What I can say:

On an earlier revision prototype of our product we used CC1070 and we were able to improve some issues by greatly reducing FS/PLL bandwidth. Now we're using CC1175 and I would like to try implementing similarly low PLL bandwidth.

Thanks much for your help!

0 Lance Carlson over 11 years ago in reply to TER

Prodigy 85 points

Hi,

Any update on my question about lowering PLL Bandwidth?

Thanks!

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CC1175 - can Frequency Synthesizer loop bandwidth be adjusted lower with external components?