Functionality of PLL

John Morley

Other Parts Discussed in Thread: LMX2485E, LMX2485

I am seeking a low power PLL to generate a high frequency (~1.56GHz) for the downmixing of a GPS signal. I don't have much experience with PLLs and there aren't many great sources on them online. I am looking at the LMX2485QE chip. If I feed this PLL a ref. oscillator, say, around 100MHz(I'm aiming towards anything south of 500MHz or so), is it capable of outputting a frequency of around 1.4-1.5GHz? If I feed it an even lower ref. oscillator, can I expect the same?

over 9 years ago

0 Julian Di Matteo over 9 years ago

TI__Expert 4085 points

Hi John,

Thanks for your interest in our products. The LMX2485E RF PLL can generate an output from 50MHz to 3.0 GHz so yes, 1.4-1.5GHz would work.

The reference oscillator can be in the range from 5MHz to 110MHz.

Hope this helps!

Best Regards,

Julian

If my post answers your question, please click on "Verify Answer" button.

0 John Morley over 9 years ago in reply to Julian Di Matteo

Prodigy 30 points

Thank you very much for answering, that was the gist I was getting from the data sheet. Can you describe how exactly the desired output frequency is specified to the chip?

0 Julian Di Matteo over 9 years ago in reply to John Morley

TI__Expert 4085 points

Hi John,

Please look at the LMX2485E User's Guide to get started. The LMX2485 is programmed via SPI.

Have you downloaded code loader? it is our GUI to program the PLL.

Setting the desired input and output frequency, among other settings, you can program the device. You can also export the register settings from code loader.

Best Regards,

Julian

If my post answers your question, please click on "Verify Answer" button.

0 John Morley over 9 years ago in reply to Julian Di Matteo

Prodigy 30 points

Ah, I see now. I probably should've taken a look at the user's guide before posting here. Thanks again.

Clock & timing

Clock & timing forum

Functionality of PLL