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LMX2572: Manual ramping issues

Thomas Malengreaux
Prodigy 30 points
Other Parts Discussed in Thread: LMX2572EVM

Hello,

I own a LMX2572EVM board (evaluation module) with the Reference PRO board. The hardware setup is identical to the one proposed in the LMX2572EVM Evaluation Module document.

To control the system, I use the TICS Pro software.

My goal is to generate a frequency sweep between 2400 MHz and 2500 MHz in 1 MHz steps on the RFoutAP output.

In my opinion, I think the manual ramp is the best fit for my needs where the frequency is incremented by the value of step 1 MHz (RAMPx_INC) all the rising edges on RampClk up to 2500 MHz and then decremented up to 2400 MHz.

The problem is that even when trying simpler manual ramps, I don't observe any frequency change on the spectrum analyzer.

I am new to your system and to PLLs in general. Can you tell me what parameters need to be set in the software to get what I want?

If the 1 MHz step is not feasible, this value can be increased.

Thank you.

Translated with www.DeepL.com/Translator (free version)

  • 0
    TI__Guru* 85330 points

    Hi Thomas,

    Could you provide your TICS Pro configuration file to us? in Tics Pro, File --> save.

  • 0 in reply to Noel Fung
    Prodigy 30 points

    Hello,

    Thank you for your fast answer.

    You can find in attachment my configuration file.

    Finally I think my manual ramp is working. Now I can vary the frequency between 2.4 GHz and 2.5 GHz with a step of 1 MHz by manipulating the "Clock Ramp" and "Reverse Direction" buttons. I think the problem was that I didn't set PLL_DEN = 2^32 - 1.

    Can you take a look at the file and tell me if it can be improved?  And give your opinion on it? 

    However, I still can't use the automatic ramp. For the project, I would like the frequency sweep to be automatic and repeat itself indefinitely (without clicking manually on the "Clock Ramp" and "Reverse Direction" buttons).

    For me, I see 2 options : 1) using the automatic ramp (that I can't manage to use) or 2) using the manual ramp with external signals on RampCLK and RampDIR.

    What do you think about that?

    Thank you.ramping_02.tcs

  • 0 in reply to Thomas Malengreaux
    TI__Guru* 85330 points

    Hi Thomas,

    What is your target ramp up and ramp down time between the two frequencies?

  • 0 in reply to Noel Fung
    Prodigy 30 points

    Hello Noel,

    1 second between the 2 frequencies (2.4 and 2.5 GHz) to start would be good.

    Thereafter, the duration will probably be reduced. 

    Thank you

  • 0 in reply to Thomas Malengreaux
    TI__Guru* 85330 points

    Hi Thomas,

    I am afraid you have to use manual ramp mode if the duration is 1s. 

    In automatic ramp mode, the frequency will be incremented at a rate equal to fpd. 

    There are 100 steps between 2.4G and 2.5GHz with a 1MHz step size. 

    100 steps in 1s means each step takes 10ms. If we use automatic ramp, then fpd = 100Hz which is definitely not a good phase detector frequency.