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LMX2572: Ramp generation

Tech A
Prodigy 40 points
Part Number: LMX2572

Tool/software:

Is it Possible to achieve
Frequency sweep 1 (in Ramp Up-Down configuration):
Start: 2.4 GHz
Stop: 2.485 GHz
Sweep time/sweep rate: 0.1 μs/ 10 MHz

Frequency sweep 2 (in Ramp Up-Down configuration):
Start: 5.725 GHz
Stop: 5.85 GHz
Sweep time/sweep rate: 0.1 μs/ 10 MHz

If not achievable Provide us with alternative methods with which i will be able to achieve in detail.
And what is the Minimum Time period with which i can sweep the 150MHz band.
If i disable the Vco Calibration will it effect my Ramp Signal Drastically. 

  • 0
    TI__Guru** 107890 points

    Hi There,

    calibration-free ramp range is less than 80MHz at VCO frequency. In your application, you need to have multiple VCO calibrations during the ramp period. There will be big glitch when the VCO is calibrated. 

    in addition, your requested ramp duration is still too short for LMX2572. I don't think LMX2572 or any other synthesizer can support.

  • 0 in reply to Noel Fung
    Prodigy 40 points

    Hi,
    can we just urn off vco calibration and get desired output 
    what is the least time period which can be achieved using this ic for band of 150MHz

    Can u suggest any other ic or  integrated solution for the above specification

  • 0 in reply to Tech A
    TI__Guru** 107890 points

    Hi There,

    We can operate the device in full assist mode to skip vco calibration. To sweep the frequency, you need to keep programming the device to lock to different frequencies over time. 

    There are a few more registers to write, in full assist mode, when changing the vco frequency. Let's assume we need to write 5 registers to change the frequency, at the max. SPI speed, it takes 40ns to complete the registers write. The device only has 60ns to response and change frequency, I don't this is enough to the device. 

    Please check with the DAC team (in Data Converters forum) to see if they have something suitable to you. 

  • 0 in reply to Noel Fung
    Prodigy 40 points

    Hi
    what is the least time period which can be achieved using this ic for band of 150MHz

  • 0 in reply to Noel Fung
    Prodigy 40 points

    Hi

    Vco calibration or Vco frequency change is compulsory ?
    Do u have any document so that i can understand the whole process in detail 

  • 0 in reply to Tech A
    TI__Guru** 107890 points

    Hi There,

    When the amount of VCO frequency change is big enough, a VCO calibration is required. 

    Below appnote explains this.

    https://www.ti.com/lit/pdf/snaa336