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LMX2820: Are two RF outputs independent of each other?

Chenggang Xie
Prodigy 10 points
Part Number: LMX2820
Other Parts Discussed in Thread: LMX2595,

If the frequencies at two outputs can be different, what is the restriction? Can LMX2595 do the same or only one frequency for both outputs? Thanks.

  • 0
    TI__Genius 11900 points

    Hello Chenggang,

    Both the outputs are linked to the same VCO frequency, however in the LMX2820, each RFoutX has it's own channel divider which can be 2,4,8,16,32,64 or 128.

    For example you can have a VCO of 8 GHz, divide one output by 4 to 2 GHz, while you divide the other by 8 to 1 GHz. This was not possible on the LMX2595 where both the outputs used the same channel divider value.

    In both devices, you can set one output to direct VCO (8 GHz according to the above example) and the other output to channel divider.

    Thanks,

    Vibhu

  • 0 in reply to Vibhu Vanjari
    TI__Mastermind 33790 points

    Chenggang,

    Quick follow-up from LMX2820 datasheet section 7.3.8:

    The channel divider is actually a single divider with multiple segments and tap points that is shared between RFOUTA and RFOUTB. In general, this can operate as independent divider values with the one exception that if a divide value of 128 is chosen for one output, then this divide must be chosen for the other output (although the channel divider can still be bypassed). Note that when the output frequencies are not the same, the higher frequency output will have sub-harmonic spurs at frequency offset equal to other output.

    Regards,