LMX2571 external VCO range .

user5270002

Hi， Sir

From the datasheet the lowest external VCO frequency is 100MHz, Can I use a 77MHz- 90MHz external VCO? It does not work or lose some performance ? if lose some performace ,wht is it?

Thanks

over 8 years ago

0 Puneet Sareen over 8 years ago

TI__Expert 8865 points

Hello Tg,
Thanks for your question.
Your request is assigned to an expert and he will get back to you soon.
Best regards
Puneet

0 Dean Banerjee over 8 years ago

TI__Mastermind 28031 points

TG,

The reason for a lower slew rate on this device is because at lower frequencies, the slew rate of the signal is lower, and any noise riding on this signal can cause the N divider to miscount. So if you were to use a high slew rate signal (like a square wave), it is highly likely this would work. I would not expect any phase noise degradation as long as you have a faster slew rate signal. Also, if you use the output divider, this can have an impact on the sensitivity. In any case, if you have a high slew rate signal or square wave, then the device will likely work to 77 MHz.

That being said, the electrical specification is 100 MHz. So if you were to run into any issues that occur only below 100 MHz, TI would NOT be responsible for this.

Regards,

Dean

0 user5270002 over 8 years ago in reply to Dean Banerjee

Prodigy 20 points

Thanks for youe help. I 'll raise the FIN signal amplitude and add some filter .

TG

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LMX2571 external VCO range .