This thread has been locked.
If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.
Part Number: LMK03318
Could you kindly help on the questions below, thanks?
1. Use REF1 for 25MHz reference, but it is 24.9999MHz, do you think this will cause the output frequency is a bit lower than set?
2. How many methods to fine-tune these output frequency? Could change the fraction-divider works? any other method?
3. If I change the fraciton-divider register while the PLL working, will the setting active immediately? or I need power on reset?
The PLL output will follow the reference input precisely. For example, your reference input is off by -4ppm (-0.0001/25*1e6) then your output will also be off by -4ppm. So instead of, say, 100MHz output, it will become 99.9996MHz.
There are two methods to fine tune output frequency. One is by tuning numerator of fractional divider, the other is to fine tune the load capacitance the crystal, if an XTAL is used. In general, load capacitance tuning is recommended because it introduces no degradation in phase noise. Fractional numerator tuning, on the other hand, can add additional fractional spurs. Please refer to this appnote for more details: http://www.ti.com/lit/an/snaa281a/snaa281a.pdf
A soft reset is needed after changing the fractional divider in order to recalibrate the PLL.
Clock and Timing Systems & Applications
To view training videos on Clock and Timing Solutions please visit TI Precision Labs
More information Clock and Timing System products: http://www.ti.com/clock-and-timing/overview.html
We are glad that we were able to resolve this issue, and will now proceed to close this thread.
If you have further questions related to this thread, you may click "Ask a related question" below. The newly created question will be automatically linked to this question.
In reply to Hao Z:
Thanks a lot, Hao.
All content and materials on this site are provided "as is". TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with regard to these materials, including but not limited to all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement of any third party intellectual property right. No license, either express or implied, by estoppel or otherwise, is granted by TI. Use of the information on this site may require a license from a third party, or a license from TI.
TI is a global semiconductor design and manufacturing company. Innovate with 100,000+ analog ICs andembedded processors, along with software, tools and the industry’s largest sales/support staff.