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DAC38RF82EVM: CONFIG clock

Expert 1490 points

Replies: 7

Views: 51

Part Number: DAC38RF82EVM

According to the DAC38RF82EVM SCH, the LMK04828 can be program from the GUI. Which means that no need of TSW14J56 board for program this PLL. 

I like to use on-board VCXO clock mode by shunt JP3 pin1 and pin2. Which is PLL2 only. 

By setting-up followings to get VCO at 2457.6MHz

1. the OSCin Freq is >63MHz to 127MHz

2. Doubler 1x

3. R = 1

4. Prescaler = 4

5. N divider = 5

6. VCO Mux = VCO0  

7. update mode is Immediate

However, the PLL2 is not locked - LED (D4) is not ON. 

Did I miss anything? Thank you.

  • Guru 68480 points

    VCXO = 2457.pptxNew2day,

    Please see settings in attached file.

    Regards,

    Jim

  • In reply to jim s:

    Hi Jim,

    That's what I have. I've set OSCin Freq at 63 ~ 127MHz too. Didn't lock. 

    I notice that only OSCINn path is populated not OSCINp, Was it OK? 

    Also J25 is on OSCINn path not OSCINp. Was it OK? 

    Normally it's using P end/path for using DIFF as single-ended. 

  • Guru 68480 points

    In reply to new2day:

    LMK_2457.6MHz.cfgNew2day,

    Make sure to enable the charge pump by setting address 0x169 to 0x59. Also select VCO by setting address 0x138 to 0x0. See the LMK settings in the attached config file.

    Regards,

    Jim

     

  • In reply to jim s:

    Hi Jim,

    I have no luck and did followings to make it simple, which is PLL2 only. 

    1. remove C49 and install C366 to use J25 as OSCin

    2. set PLL2 as stated in table 8 Single-Loop Mode, see also screen-shot attached

    3. apply 100MHz at 13dBm on J25 so VCO1 is 3000MHz

    4. set both register 0x15F and 0x16E to 0x13 for PLL2 Locked 

    5. enable OSCout also to CMOS norm/off and see output at pin40 (OSCOUTP)

    Still could not get PLL2 locked. 

    Thank you and regards.PLL2_not_Locked.pdf

  • In reply to jim s:

    Hi Jim,

    I have no luck and did followings to make it simple, which is PLL2 only. 

    1. remove C49 and install C366 to use J25 as OSCin

    2. set PLL2 as stated in table 8 Single-Loop Mode, see also screen-shot attached

    3. apply 100Mhz @13dBm on J25 so VCO1 is 3000MHz.

    4. set both register 0x15F and 0x16E to 0x13 for PLL2 Locked 

    5. enable OSCout also to CMOS norm/off and see output at pin40 (OSCOUTP)

    Still could not get PLL2 locked. 

    Thank you and regards.8015.PLL2_not_Locked.pdf

  • Guru 68480 points

    In reply to new2day:

    What frequency is the clock on J25 and what frequency are you trying to achieve with the VCO? I noticed you still have the charge pump tri-state selected. This has to be unselected. Try removing R54 as well. 

  • In reply to jim s:

    Yes, it's the charge Pump Tri-State. Now LED D4 is ON. 

    I'm trying to get both 2500MHz and 3000MHz VCO Freq for now. 

    Thank you.