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LMX2594: Level output not as expected, programming s

stephen lyons
Prodigy 50 points
Part Number: LMX2594

Have a TI LMX2594 on a pc with resistive 50 ohm termination into a Marki BAL-0620SMG for differential to single-ended conversion.  The output power level is far 

less than expected;  The Marki BAL-0620SMG is specifically designed for 10 ohm to 50 ohm conversion;  I could understand some path loss but we're seeing excess,

question: should be no problem using the TI LMX2594 output differential with 50 ohm termination into a Balun ? 

we simply took the register sequence produced by using the TICS gui for the LMX2594; produces the exact frequency but the level is much lower than expected ( should be max 3dBm SE @ 10GHz)

question:   do we have to write all register every time we program

question:   would the register sequence from the TICS gui be the only step? 

question: The datasheet recommends 1) power on, 2) reset = 1 (R0), 3) reset = 0, 4) program (presume all registers at once),

5) program R0 FCAL_EN = 1

For the reset and FCAL_EN program ca we just write R0 into the device?  Would it understand that? or do we need to write all the registers each time with the reset and FCAL_EN bits set ?

Thanks,

  • 0
    TI__Mastermind 28011 points

    Stephen,

    Our output power is 50 ohm pull-up to 50 ohm load, single-ended.  So I would think that you would want the load to be 100 ohm.   You balun you say is 10 ohm to 50 ohm.  Could this be 100 ohm to 50 ohm?   Another thing is this balun would need to be AC coupled.

    As for programming, the TICSPro GUI is a very helpful resource.  When you change frequency, you only need to write the registers that are changing.  Then at the end, you need to write register R0 with the FCAL_EN bit high.

    Regards,

    Dean