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LMX2572: mechanical vibrations can cause spurious interference within 5 kHz of the signal output by the lmx2572.

Lucas James
Prodigy 10 points
Part Number: LMX2572
Other Parts Discussed in Thread: LMX2594

Why mechanical vibrations can cause spurious interference within 5 kHz of the signal output by the lmx2572.

We use the LMX2572 as the local oscillator signal of a receiver, but generate an interference signal after adding a fan to the receiver.

We have proven to be mechanical vibration disturbances rather than conducted interference from fans. When the fan draws power from the board through the wire, but does not touch the receiving structure, the output signal of the LMX2572 is such that there is no interference.

Our other local oscillator LMX2594 also has the same problem.

We have proven to be mechanical vibration disturbances rather than conducted interference from fans. When the fan draws power from the board through the wire, but does not touch the receiving structure, the output signal of the LMX2572 is such that there is no interference.

  • 0
    TI__Mastermind 31820 points

    Hello Lucas,

    We have seen cases where the piezoelectric effect in ceramic capacitors in the loop filter can cause mechanical vibration to couple into the output as electrical noise. There are other constructions such as film capacitors which are less susceptible to piezoelectric effects, so first consider swapping out the loop filter capacitors. If there are ceramic capacitors in the input or output coupling paths, it may be a good idea to switch these out as well. Generally supply capacitors should not make much difference, since the on-chip LDOs have substantial PSRR at vibration frequency ranges.

    Regards,