• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 20 subscribers
  • Views 491 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LMK04832EVM: Default configuration not working

Eduardo Mendes
Prodigy 80 points
Part Number: LMK04832EVM
Other Parts Discussed in Thread: USB2ANY

Problem:  I have followed instructions from user guide quick start configuration:
1) Connected 4.5V power supply to external jacket
2) 122.88MHz applied to IN1
3) Connected USB2ANY
4) loaded default configuration

ISSUE: The current on the power supply is 0.727A and PLL lock status (STATUS_LD1 and STATUS_LD2) are off

I can manage the PLL lock if not using external VCXO so I suspect problem is coming from there.

  • 0
    TI__Mastermind 28530 points

    Hello Eduardo,

    Eduardo Mendes said:
    I can manage the PLL lock if not using external VCXO so I suspect problem is coming from there.

    This means you adjust the PLL2 R MUX to take from CLKin1, then PLL2 locks?

    Can you confirm an ~122.88 MHz signal from the VCXO?  If there is an issue with the VCXO, then neither PLL1 or PLL2 would lock as you indicate.

    73,
    Timothy

  • 0 in reply to Timothy T
    Prodigy 80 points
    Exactly. If I set PLL2 RCLK MUX to PLL1 CLKinX, the PLL2 locks.

    What I observed is the following:
    Before I programmed the PLL (just after power on). I can see a 122.88MHz signal from the VCXO.
    Once I program the board with default configuration, this signal disappears.

    thank you,
    Eduardo
  • 0 in reply to Timothy T
    Prodigy 80 points
    An additional information:
    I see VCC_VCXO stable at around 2.3V before and after programming
    Before programming, VTUNE1 is around 0V, after programming it becomes 3.3V
  • 0 in reply to Eduardo Mendes
    TI__Mastermind 28530 points
    Hello Eduardo,

    You should measure 3.3 V for that VCXO.

    If you change the CP polarity for PLL1, perhaps the Vtune will go back to 0 V and the device will oscillate again? (This of course isn't a solution but perhaps an explanation why the VCXO goes down).

    As a debug about the 2.3 V for VCXO, you might bypass the LDO for VCXO by removing R373 which connects LDO to Vcc from input. Then moving R19 to R54 to select the direct input supply. ** Because you're not using the LDO for VCXO, you'll need to reduce your input voltage to say 3.6 V so as to not over-voltage the VCXO.
    > Would you be able to check this?

    73,
    Timothy