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LMX2820: How is the INSTCAL_DDBLR_EN used

Fred Schader2
Prodigy 70 points
Part Number: LMX2820

Hello

My understanding of the use of INSTCAL is that after applying the VCO band 3/4 transition patch I need to start a calibration at the low end of the VCO range (5650 MHz) and execute a normal calibration to build a full band look up table.  What is the difference in operation between having bits zero and one of R1 (normal INSTCAL_EN, and INSTCAL_DBLR_EN)?

If i need to operate both in the non-doubled and doubled portion of the frequency range do I need to do a look up table generation for both?

thanks

Fred

  • 0
    TI__Guru* 93670 points

    Hi Fred,

    If you will need to use the VCO doubler, you should also set INSTCAL_DBLR_EN=1 during instant calibration so that the calibration will calibrate the tracking filter. You will expect a longer calibration time. 

    Recommended instant calibration programming sequence:
    1. enable all Double Buffer bits
    2. if VCO doubler is needed, enable INSTCAL_DBLR_EN
    3. Vcc power up the device
    4. Program all the registers to make the device lock to 5650MHz (INSTCAL_EN = 0, FCAL_EN=1, INSTCAL_PLL_NUM = according to your configuration)
    5. After it is locked, program INSTCAL_EN = 1
    6. Program FCAL_EN = 1
    7. Wait 100ms
    8. Program FCAL_EN = 0
    9. Instant calibration is complete

  • 0 in reply to Noel Fung
    Prodigy 70 points

    Thank you for the reply.  However, you did not answer my second question.  If I need to operate in both the doubled and non-doubled portion of the output range do I need separate calibrations for both parts.

    For example I need to sweep from 8 to 16 GHz which requires that I start using the doubled output after 11.3 GHz will I need to re-calibrate with the doubler enable bit set?

    thanks

    Fred

  • +1 in reply to Fred Schader2
    TI__Guru* 93670 points

    Hi Fred,

    If you have enabled INSTCAL_DBLR_EN during instant calibration, you don't need to do any calibration for any frequency (doubled or non-doubled) afterward.