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LP5912: How to get clean DC supply from noisy environment?

tojijn Twu
Intellectual 280 points
Part Number: LP5912

Dear SENIOR :

 I am troubled long time how to get a clean DC supply in the serious EMI noisy environment.

 My F5419A sometimes reboot in the bad DC supply, but PC and PLC are working perfectly.

 Someone told me that the high frequency (>1MHZ) DC2DC switching power can overcome the noise and get a clean DC power.

The frequency is the higher the better.And it is also the stable reason of PC and PLC

  

Does SENIOR agree with the description or have different view ?

 

THANKS

  • 0
    TI__Genius 14245 points
    Hi Tojijn,

    Unfortunately if you are having noise issues from an input supply (DC to DC) at frequencies above 1MHz very few LDOs can filter out much of that noise due to having bandwidths at or below 1MHz. You can see this in the PSRR graphs shown in most LDO datasheets. There will often be a spike in the PSRR performance somewhere between 500kHz and 10MHz, this is due to the output capacitor and not the LDO itself. If you are using the LP5912 in your application, then the size of the output capacitor is limited to 10uF, however you can increase the size of the input capacitor and have the same effect on the PSRR/filtering performance.

    One important thing to note is that in EMI noisy environments, the layout of the PCB is critical to avoid creating antennas which pick up the radiated noise. The best LDO/filter cannot do anything to filter out noise which is picked up by an antenna on the output of the LDO, it can only filter out noise which passes from the input to the output through the LDO/filter.

    -Kyle
  • 0 in reply to Kyle Van Renterghem
    Intellectual 280 points

    Dear Kyle

    I really want to completely understanding about the DC power design how to reject EMI from radiation or conduction .

    Could you nice to introduce some book or website to me?

    Thank you for all your assistance.I really appreciate your help in resolving the problem.

     

    tojijn