AR# 69977

XAPP1241 - What is the convergence time for PICXO?


How do I calculate the PICXO convergence time?


The PICXO convergence time follows the standard rules for a second order PLL. The greater the damping, the longer the PLL takes to settle. 

The less damping, the more the PLL will ring and also take longer to settle.

It also depends on what criterion is used to determine settling for the application.

It might be reasonable to assume a time of at least 10x the bandwidth time constant as a minimum for the loop to settle with a loop that is not significantly over or under damped.

The bandwidth time constant can be calculated using 1/(2*pi*f), with f being the bandwidth frequency. 

In the spreadsheet provided along with the PICXO reference design, by default the graph plots the data point for -6dB. 

For time constant calculation, use -3dB for better approximation.

AR# 69977
日期 09/28/2018
状态 Active
Type 综合文章
器件 More Less