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Original question:

LM60430-Q1: Power Designer part values are not even close to typical values on data sheet....

LM60430-Q1: Poor simulation

Jim Smith79
Prodigy 130 points
Part Number: LM60430-Q1

When the values of components given in the data sheet are put into the simulation program they do not even come close to passing CISPR 25, and when I use just the simulation tool, minor changes cause erratic changes in other components, with some components always jumping back to a default value.  I like this part, the product description sounds good, and the on-line simulation tool is handy, BUT I cannot trust the results... I did a prior design with a TI part and the simulation tool, and it did not pass. TI seems to be the big player in these switching regulators, but it is all a shell game if the design tools do not work. I might as well be guessing as to what parts to use....

  • 0
    TI__Mastermind 23815 points

    Hi, 

    In general the simulation is provided as a guideline for the behavior of the part given its operating condition.

    As for EMI / EMC it also depends on other factors such as board layout which greatly affects your result. 

    I think the best way to see how the part perform is to run the simulation then check the result on the EVM since nothing beats the actual bench value.

    I believe for this part LM60430-Q1 EVM we provided the conducted emission data on the user guide. 

    https://www.ti.com/lit/ug/snvu693/snvu693.pdf?ts=1633628092511&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FLM60430-Q1

    I hope that helps. 

    Thanks

    -Arief

     

  • 0
    Prodigy 130 points

    Yes, I have ordered an EVM board, but the big problem is that it if I put those part values into the simulator tool, the circuit fails CISPR25... It even violates the part size directions of the data sheet.  That cop-out of "As for EMI / EMC it also depends on other factors such as board layout which greatly affects your result.", but reducing the critical PCB layout requirements is one of the selling points for this chip...  I am tempted to just copy the BOM of the EVM board, although I do not have the extra room for all the copper that it has used-up....

  • 0 in reply to Jim Smith79
    TI__Mastermind 23815 points

    Hi Jim,

    Yes i understood your issue.

    EMI is a tricky issue and there is different mitigation techniques that tackles each type of noise whether its differential noise or common mode noise. Differential noise is a bit easier to tackle since an LC filter would do majority of the job.

    As for common mode noise is a bit harder since it depends on the layout and you may need common mode choke for this. 

    As for the filter components for LM60430-Q1 the value of 3.3uH and 2x4.7uF gives you the corner frequency of 28.57kHz. At 285 kHz (1 decade) it should attenuate the noise by 40dB. Your fundamental noise on this part is located at 400kHz.

    My experience with EMI is to prepare for the worst, normally i put a placeholder for extra capacitor if needed as well as other mitigation techniques such as snubber network or adding boot resistor to slow down the SW rising edge. 

    We also try our best to develop an IC to help to make it easier for our customer to tackle this EMI issue with some features  such as spread spectrum, integrated input capacitor, etc. You can see other IC that we develop with this EMI in mind such as the one below. 

    https://www.ti.com/lit/ds/symlink/lmq61460-q1.pdf?ts=1633740672626&ref_url=https%253A%252F%252Fwww.google.com%252F


    But again testing iton the EVM would be better to gauge each part performance against EMI. 

    We also can review the part layout and provide any assistance that we can. 

    Thank you

    -Arief