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Frequency of Output Ripple Voltage of LM2698

Orionsbelt
Prodigy 60 points
Other Parts Discussed in Thread: LM2698

Hello, 

I am designing a power supply for a highly-sensitive accelerometer. The accelerometer requires a maximum input noise of 100uV/sqrt(Hz). My chosen power supply has an output ripple voltage of 13.75mV, which will affect the measurement of the accelerometer. Now, I have used the TI WEBENCH and the suggested design is to use an LM2698 boost converter, which is suitable for my solution. But in the design report, provided by the TI, the frequency of the output ripple voltage is not mentioned. 

Hence, I wonder whether the frequency of the output ripple voltage has the same frequency as the switching frequency of the converter? According to the design report of LM2698, the switching frequency is typically 600 kHz, since the FSLCT is connected to the ground. 

I am uploading the design report which might help you further.

Best regards
T.KBasic Design Report.pdf

  • 0
    TI__Intellectual 2225 points

    Hi Tanzim,

     

    Yes, the fundamental frequency of the output ripple will be the same as the switching frequency of the converter. There will be additional higher frequencies (harmonics) as well, but they will be of lower amplitude than the fundamental.

    To get to the 100uV/sqrt(Hz) level, you may need to add a CLC filter.

     

    Perry