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LMX2572EVM: Question about the loop filter components that are installed on the LMX2752EVM development board

Mark Schutzer
Prodigy 10 points
Part Number: LMX2572EVM
Other Parts Discussed in Thread: LMX2572

I would like to know the actual loop filter values that are installed on the LMX2572 development board?  The loop filter components documented in the LMX2572EVM Evaluation Instructions do not match what is actually populated on the EVM board.  I just recently received the EVM board and I believe that the board is probably a newer revision than the version represented in the instructions.

The board I have has loaded components where the instructions call out DNP's and the resistors populated in the loop filter are different values from the documentation.  In addition the board that I have is equipped with a 100 MHz crystal reference oscillator populated where the instructions say the board is shipped configured for external reference clocking.

Is it possible to get a schematic of the LMX2572EVM board as it is currently shipping, or alternatively just get the current loop filter component values as installed in the currently shipping boards.

Thanks,

Mark Schutzer

  • 0
    TI__Guru* 85330 points
    Hi Mark,

    I am sorry for the inconvenient caused. Right, there were some errors in the EVM, I just found this out recently. The original design should follow EVM User's guide. In the actual EVM, there are two discrepancies. (1) the default reference clock source is now using the on-board XO. So, you will find the current consumption do not match with EVM User's guide. (2) the loop filter is not correct, so the default loop bandwidth becomes 30kHz.
    If you want to get the performance as said in the EVM User's guide, please change the loop filter as shown in the schematic. You can keep the on-board XO, which is a good reference clock anyway.