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Original question:

LMK05318BEVM: 1PPS on LMK05318BEVM

LMK05318BEVM: 1PPS on LMK05318BEVM

Coline B
Prodigy 30 points
Part Number: LMK05318BEVM

Tool/software:

Hi !

The precedent thread has been locked so I continue here.

I've got a 1Hz signal (this is the GPS' synchronization PPS) that arrives in the LMK05318BEVM.

I would like to have this same signal coming out of the LMK05318BEVM (synchronized in frequency and phase with the input one) when everything is fine and if I stop the input signal (for a long time, like one or two days), I would like the output signal to continue as if the input signal had never stopped, still synchronized in frequency and phase with the one that stopped.

I did something on TICSPRO that you'll find here :

2024-12-09_CONFIG_LMK05318B EVM_1PPS.tcs

When we look to the status, it seems that the component don't detect the input signal.

Can you give me a fonctionnal TICSPRO file that works with the evalboard LMK05318BEVM please ?

Thank you,

Have a nice day,

Coline

  • 0
    TI__Genius 16565 points

    Hi Coline,

    Please try with the default 1 PPS configuration found in TICS Pro. A 12.8 MHz XO input is required with this configuration to get the DPLL to lock.

    Make sure to download the latest TICS Pro version here: https://www.ti.com/tool/TICSPRO-SW.

    Regards,

    Jennifer

  • 0 in reply to Jennifer Bernal
    Prodigy 30 points

    Hi Jennifer,

    Thanks for the answer. So we can't use the evalboard for 1PPS input without changing the XO on it ? (Or only using an external XO)

  • 0 in reply to Coline B
    TI__Genius 16565 points

    Hi Coline,

    That is correct, an external XO input is required to use the TICS PRO default 1-PPS config.

    We recommend a lower XO frequency for the following reasons:

    When configuring a 1-PPS input, only the 1-PPS Phase Detector and Validation Timer can be enabled for reference validation.

    The 1-PPS phase detector determines the required XO ppm accuracy through the PRIREF_PH_VALID_THR register. The counter has a maximum value of 63.

    If the XO ppm exceeds the required phase detector accuracy, then the 1-PPS reference will not be detected.

    • Equation:
      • XO accuracy [ppm] = PRIREF_PH_VALID_THR / [(XO frequency [MHz] * (OSCIN_DBLR_EN + 1)]       
    • Required accuracy for 48 MHz XO input:
      • XO = 48 MHz
      • PRIREF_PH_VALID_THR  = 63, maximize XO accuracy range
      • Required XO accuracy =  63 / 48e6 * 1 = ± 1.3125 ppm without doubler
    • Required accuracy for 12.8 MHz XO input:
      • XO = 12.8 MHz
      • PRIREF_PH_VALID_THR  = 63, maximize XO accuracy range
      • XO accuracy [ppm] = 63 / 12.8e6 * 2 = ± 2.46 ppm with doubler or 
      • XO accuracy [ppm] = 63 / 12.8e6 * 1 = ± 4.92 ppm without doubler
      • We recommend 12.8 MHz XO input to allow a larger ppm margin.

    Regards,

    Jennifer