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LMK04828: no output on DCLKout12 at distribution mode

Yoonsun Kim
Expert 1860 points
Part Number: LMK04828
Other Parts Discussed in Thread: LMK04832

Hi,

I set lmk04828 as distribution mode on reference to table 10 on page 55, datasheet.

10MHz is supplied to CLKin1 as AC coupled LVDS. I checked it by oscilloscope.

I expected 10MHz clock on DCLKOUT12 but there was no signal.

The registers I set were as follows. The others were default.

0x13f --> 0x00

0x140 --> 0xf7

0x173 --> 0x60

0x147 --> 0x00

0x138 --> 0x40

0x137 --> 0x01

0x133 --> 0x02

Regards,

YS 

  • 0
    TI__Genius 10995 points

    Hello YS,

    To set up your device in distribution mode, did you just change the registers according to that table in the data sheet or did you also set the distribution mode in TICS Pro? If not, this is how it's done:

    1. I recommend setting the TICS Pro back to the EVM default to make sure all registers that should be set a specific way are set correctly

    2. Go to the tab "Set Modes" on the left menu and click on "Set Distribution"

    That should set the distribution mode correctly. Also, based on your description, I have created and attached the .tcs file that should match your use case.

    LMK04828_Dist_No_Outputs.tcs

    Good Luck,

    Andrea

  • 0 in reply to Andrea Vallenilla
    Expert 1860 points

    Hi Andrea,

    I checked the file you attached and found out it is for lmk04832. Anyhow, I made a new tcs file from TICS pro as your advice.

    I set DCLKout12 to Bypass and SDCLKout13 to SYSREF and programmed the values saved by TICS pro  and checked outputs by oscilloscope.

    10MHz was appeared on DCLKout12 but different clock was appeared on SDCLKout13 than I set.

    I set SYSREF Clock Divider to 32 and Clock Output Select of SDCLKout13 to SYSREF. I expected 0.3125MHz(=10MHz/32) but about 0.833MHz(=10MHz/12).

    I have no idea why SDCLKout13 is different from TICS pro GUI result. I attached the tcs file.

    Can you check and give me any clue?

    LMK04828_clkin1_distribution_2022_1117_distribution_bypass.tcs

    Regards,

    YS

  • +1 in reply to Yoonsun Kim
    TI__Genius 10995 points

    Hello YS,

    In order to use the SYSREF divider when in distribution mode, you have to set the SYSREF MUX to choose pin 3 (Continuous SYSREF), as demonstrated by the green path below from TICS Pro:

    To do so, click on the "Continuous" button at the top of the SYNC/SYSREF screen:

    Check to see if that results in the correct frequency being outputted, if not toggle the SYNC_POL register or SYNC_EN pin on the "Other SYNC Controls" gray box on the top right. 

    Good Luck,

    Andrea