LMX2581- KVCO

Hi Lahatra,

We received your question. Thanks for your interest in our products. I forwarded your query to the applications engineer most familiar with this device.

We appreciate your patience.

Regards,
Julian

Lahatra,

A little while back, we updated the LMX2581 datasheet with the most recent information on the VCO gain and the VCO cores.  This is the best data we have.

Also, I would encourage you to try the PLLatinum Sim for PLL design as it is much more powerful and up to date on the LMX synthesizer products.

Regards,
Dean

Thank you Dean,

Based on this your answer, I suppose that the right information of the VCO gain (KVCO) is as simulated in the PLLatinium.

The KVCO is not the same for each tool (18 MHz/V for the Clock design tool and 22 MHz/V for the PLLatinium for the same frequency)

Anyway, let me know to have a guarantee from the TI that the VCO gain (KVCO) specifications of the LMX2581 would not change again

as the realised prototype based on this PLL LMX2581 is under qualification.  

Regards,

Lahatra

Lahatra,

I am suspecting that the VCO gain change you are seeing is likely due to a difference in the VCO core ranges, which have been updated in the datasheet (seep Page 19). The tools use a linear approximation for the Kvco in these ranges. The datasheet is the final authority, most updated, and most scrutinized document in regards to the specifications.
The PLLatinum Sim will track datasheet updates, but updates to the Clock Design Tool database are being blocked by corporate standards.. Specifically, to update the clock design tool, we have to re-design it to meet corporate standards, and we don't have the bandwidth for that. So PLLatinum Sim is the most trustworthy simulation.

In regards to telling you that the KVCO gain will never shift again, understand that I avoid using the word "guarantee" for even obvious things that I have high confidence in as sometimes this has legal implications. This being said, I feel it extremely unlikely for these numbers to shift. I am the one who wrote the LMX2581 datasheet, clock design tool database, and PLLatinum Sim Tool design.

Also be aware that the LMX2581E version of this device has a different frequency range and this is different than the LMX2581.

REgards,
Dean

Hello Dean,

I understand the difficulty to update different tools.

PLLatinium seems very interesting for the PLL sim tool.

Ok, thank you for your answer.

Regards,

Lahatra