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LMX2594: possible mismatch in the datasheet?

Viktor Vojta
Intellectual 315 points
Part Number: LMX2594

Hello, I would like ask you the unclear explanation of the bit14 in the Register7: OUT_FORCE. There is description of the bit R0.9 "If disabled, also be sure to enable OUT_FORCE....If enabled, also be sure to disable OUT_FORCE" in the datasheet (page 46, table24, ver April 2019). It means the bit R7.14 must be always inverted value of R0.9. But in the default setting both bits have got value "0". I think, the description for OUT_FORCE is probably to strict, but I am not sure. Or is the Description correct and the default values shall be fixed during init-configuration?

  • 0
    TI__Mastermind 33620 points

    Hi Viktor,

    OUT_FORCE forces the output stage to remain active, regardless of the signal present at the buffer input. OUT_MUTE disconnects the input of the buffer during the calibration process. It's possible to have both OUT_FORCE=0 and OUT_MUTE=0, where the output during calibration will be forced off but not muted, and thus susceptible to VCO feedthrough; it's also possible to have OUT_FORCE=1 and OUT_MUTE=1, in which case the output will be forced to the MUTE state during calibration, which could introduce some AC glitch on the receiving device once the MUTE condition is cleared. The device functions with the default register settings, they just aren't necessarily optimal for most use cases. We recommend either forcing the output on and not muting the output (OUT_FORCE=1, OUT_MUTE=0), in which case the output will follow the VCO frequency as it changes; or OUT_FORCE=0 and OUT_MUTE=1, which disables the outputs, helps prevent the VCO from coupling through during calibration, and keeps the differential voltage equal during calibration to minimize glitches when the output starts up again. 

    Regards,

  • 0 in reply to Derek Payne
    Intellectual 315 points

    Thank you for fast answer with excellent explanation. Regards, V. Vojta