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Original question:

LMX2572EVM: Max bandwidth for frequency sweeping of LMX2572EVM

LMX2572EVM: Max. achievable bandwidth in Automatic/Manual Ramping mode

Amrita Kothari
Prodigy 50 points

Part Number: LMX2572EVM

Tool/software:

Hi Noel, 

Then what is the maximum achievable ramp bandwidth and could you please tell the parameters that determine it ?

Regards,

amrita

  • 0
    TI__Guru** 120050 points

    Hi Amrita,

    As shown in the datasheet, the slop is determined by RAMP_INC (in frequency) and phase detector frequency.

    This slope represents the capability of the ramp engine. Actual performance is limited by the loop bandwidth, higher slope requires wider loop bandwidth. 

  • 0 in reply to Noel Fung
    Prodigy 50 points

    I am sorry I am in the process of understanding the LMX board..so need some more clarification.



    Is delta f that is highlighted above related to the loop filter bandwidth and how do we set fTh ..what is it based off of?

    Thanks.

    Regards, 

    Amrita

  • 0 in reply to Amrita Kothari
    TI__Guru** 120050 points

    Hi Amrita,

    Suppose you want the device to ramp 50MHz in 100µs and your fpd is 100MHz.

    Frequency will increment every fpd cycle, i.e. 0.01µs. 

    Your desired ramp time is 100µs, there are 100/0.01 = 10000 ramps. (RAMP_LEN)

    Each ramp will change 50M / 10000 = 5kHz (delta f)