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LTM4700 - MFR_PWM_COMP and Ripple noise

Hi,

I'm currently working the project that uses LTM4700. I checked the ripple noise on output voltage and got a high level of ripple (~2-300mV).

So, I tried to change value of MFR_PWM_COMP with the gm and RCOMP value from LTpowerCAD. The value of this byte is changed but I didn't see any improvements.

The datasheet said we can optimize the compensation loop by modifying these parameters. Am I understand correctly?

Is there anything I missed? Please advise.

Thanks.



- Typo fixed.
[edited by: ssuphar at 3:12 PM (GMT -5) on 1 Dec 2021]
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  • Hi ssuphar, the output voltage ripple can be minimized by increasing the output capacitors. This is the most effective way to modify the ripple. However, adding the output capacitance can lower the feedback loop bandwidth, which may lead to unstable feedback loop. In this case, you can use the MFR_PWM_COMP registers to modify the gm and Rth to increase the bandwidth.

  • Hi Susan,

    Thank you for the clarifications.

    I have tried to add more capacitors at the output but did not help.

    However, I have changed measurement methodology by using a coax-bnc probe instead of a passive probe and then the ripple noise level became good. So, this could be a test setup issue.

    Thank you,

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