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LMK04832: No Clock output on my board when using a working register set (from EVM)

Erez Harek
Prodigy 10 points
Part Number: LMK04832

Support Path: /Product/Development and troubleshooting/Search the forums for my problem/

We designed a board that uses the LMK04832 to generate variable output clocks from a 100Mhz oscillator.

We've based our design on the LMK04832EVM,and the register content we use is identical to the one generated using TICS-PRO.

when configuring the chip on the EVAL board, were able to generate the required output frequency, yet, when writing the same data to the LMK chip on our board, we see that the clockout output generates a high DC signal instead of a clock signal.

We manage to read back all the register values using the SPI bus, and  they hold the expected values they were configured to

Our board design is almost identical to the EVAL board, except for the CLKin0/1 and Reset that are not connected, this forced us to change the CLKin_demux to off in order to generate Vtune.

below is our design scheme.

Any thought on why the same configuration works on EVAL board bud doesn't work on our board?

 

  • 0
    TI__Genius 9920 points
    1, The schematic didn't show loop filter for CPOUT1.
    2, Make sure the SYNC pin voltage is the same as EVM, normally it should be low.
    3, Use STATUS pins to monitor PLL1 and PLL2 lock status.
    4, Measure voltage on Vcont pin of VCXO, and measure VCXO output frequency.