feedback
Rate this webpage

Need
Support?


Ask An Expert

Our Ask An Expert knowledge base contains answers to questions from designers like you. Browse the knowledge base by category or search key words. Not seeing what you need? Ask An Expert a question of your own.
All   >>  Energy Efficiency   >>   Industrial and Home Appliances   >>   Questions
 

What is the minimum REFERENCE FREQUENCY INPUT (pin 12) clock speed, for the FS7140?

You should be using the evaluation software to determine the minimum rate for the REF input. The lower limit of F_ref is not fixed. It has to be calculated because the frequency at the phase detector (F_ref / N_ref) affects PLL stability, just like in all charge pump PLLs. Other factors, particularly the value of the feedback divider are involved in that calculation. If the reference frequency is below, say, 150KHz, it may be difficult to achieve a solution using the evaluation software. This would fall into an area where the FS7145 is approaching the loop stability limits and you should advise more details of the application (minimum F_ref that you want to use, maximum F_ref, multiplication ratio(s) being implemented). Answered by:
ON Semiconductor
2014-07-30 08:52:50.878