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Original question:

LMX2572: RAMP GENARATION

LMX2572: Increment modification in manual ramp generation

Hubert Dube
Prodigy 20 points
Part Number: LMX2572


Hi,

Is it possible to set a new value for the ramp incrementation while the PLL is running?

I am looking to sweep frequencies with a specific increment and, at the end of the sweep, restart a new one but with a different  ramp increment, without having to reprogram the whole register map.

I have tried to change the values of the increment registers, and setting FCAL_EN = 1 as read in the data sheet, but the changes don't seem to be applied.

Thank you

Hubert

  • 0
    TI__Guru** 109830 points

    Hi Hubert,

    We have to tell the chip the amount of ramp incrementation before we start a ramp. So if you want a different ramp incrementation in the second ramp, you have to wait until the first ramp finish before you can program the chip and start the second ramp.

  • 0 in reply to Noel Fung
    Prodigy 20 points

    Hi Noel,

    As I operate in manual mode, this change should be made between two RAMP_CLK pulses if I understand correctly, as there is no real end to a manual ramp?

    But is there a particular procedure to do so? Is there a way to force the registers (R98 to R103) to be read again, because even though I write new values in those registers no change is observed.

    Thank you

    Hubert

  • 0 in reply to Hubert Dube
    TI__Guru** 109830 points

    Hi Hubert,

    With manual ramp, you don't need RAMPx_LEN, all you need are RAMPx_INC. As far as I remember, after RAMPx_INC are updated, a ramp clock pulse will take the new RAMPx_INC values.

    Currently I don't have lab access I cannot verify, but if the above procedure does not work, try first of all, disable RAMP_EN, then update RAMPx_INC, then enable RAMP_EN and then provide a ramp clock to ramp.