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LM3150: is there a way to increase the output accuracy?

David Huang
Intellectual 2285 points
Part Number: LM3150

Hi team

For the application below

Vin=24V

Vout=15V

Iout=4A

Fsw=484kHz

Vout was observed 14.7V which is slightly lower than expected. I think this is normal according to the DS but is there a way to improve the accuracy?

The voltage at FB was 0.59V when the result was tested, will the output become accurate if we can make the FB 0.6V somehow? Is there any way to do so?

Regards
David

  • 0
    TI__Mastermind 27470 points

    Hi 

    can you share the schematic and output cap ESR value? as LM3150 use COT control, there is a ripple injection at FB, so the Vo=K*(Vref+0.5Vinj).  K is output divide ratio.

    you may need slightly adjust your FB divide ratio to make Vo=15V. but it still be slightly change by Vin.

    Thanks

  • 0 in reply to Daniel Li14
    TI__Intellectual 2285 points

    Hi Daniel

    Thanks for the response!

    Adding some questions here, could you please check below?

    1. For the Vout equation you mentioned, is the Vinj the injection ripple Vpp value? How to determine this value?

    2. For COT devices the frequency changes over time, I noticed that the max frequency for LM3150 is 1MHz, what would be minimum frequency for this device?

    Regards

    David

  • 0 in reply to David Huang
    TI__Mastermind 27470 points

    Hi David:

    1. yes, this value can be measured, and it is related to ESR and IL, you can refer datasheet: Determine Output Capacitance section.

    2. The Ron can make the frequency nearly fix, so it doesn't change a lot. maxim frequency is 1Mhz, min can be lower than 250Khz.

    Tks