LMX2572: Loop Bandwidth is limited to ~100kHz in PLLatinium

Samuel Lehner53

Part Number: LMX2572

Hi,

i would like to set the loop bandwidth to 200 kHz to increase the lock time. But PLLatinium limits the Bandwidth to 100kHz. I'm not sure why, maybe the input capacitance of the VCO is limiting? An active filter can remove this limit. I prefer a type b, 3.oder filter. Is it possible to invert the charge current on LMX2572?

Thanks Samuel

over 7 years ago

0 Dean Banerjee over 7 years ago

TI__Mastermind 28011 points

Sam,

On the design screen, it is "Min High Order" cap that is limiting this to 1500 pF. This is related to the VCO phase noise. Click on the LMX2572 design tips button for more details on this. If you are willing to sacrifice VCO phase noise, you can reduce this value..

Regards,

Dean

0 Samuel Lehner53 over 7 years ago in reply to Dean Banerjee

Prodigy 160 points

Hi Dean,

thank you for your help.

Samuel

Clock & timing

Clock & timing forum

LMX2572: Loop Bandwidth is limited to ~100kHz in PLLatinium