I have been using this part in a design for quite some time, there has always been an interesting relationship in the CP settings and how it affects the loop bandwidth. As you increase the CP settings it does move the loop corner but not always in the direction I would think. Sometime it comes in and sometimes it goes out and it varies PLL to PLL. Normally it hasn't been a problem but it seems this latest LOT the variation is wider and is causing problems.
Has there been a change in design or fabrication recently?
Thanks
