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Original question:

LM5169: Going Beyond Desired Output

LM5169: Humming sound from the LM5169 circuit

Abhishek Sharma
Prodigy 20 points
Part Number: LM5169

Tool/software:

Hi,

In my application I use Type 3 schematic for minimum ripple for an application of 115V input and output of 5V, 0.6A max:

 with L0= 100uH, 1 A saturation current, Ra = 178k, Ca=3300pF, Cb=56pF, Rt = 49.9k, Rfb1= 453k, Rfb2=143k, Cout=47uF, Cin=2uF

The Vout is connected to a load of 0.6A. If the load is connected to Vout  and then the input supply of 100V is turned ON the Buck functions fine, but if the load is removed while the input is ON and connected back again the buck outputs 4.2V and not 5V and the 100uH inductor creating a humming sound .

How to resolve this problem?

Thanks

Abhishek

  • 0
    TI__Expert 5490 points

    Hi Abhishek,

    Can you please share the schematic and BOM for analysis? 

    What is the inductor saturation current? Generally the humming noise is generated by the inductor current when the saturation current of the Inductor is not sufficient to handle the peak load demand. 

    Also typical voltage is 12V in your design and 115V Vin_max; I am curious is the VIN_max in your application is correct?.

    Thanks,

    Nitya

  • 0
    TI__Expert 5490 points

    Hi Abhishek,

    Can you please share the schematic and BOM for analysis? 

    What is the inductor saturation current? Generally the humming noise is generated by the inductor when the saturation current of the Inductor is not sufficient to handle the peak load demand. 

    Also typical voltage is 12V in your design and 115V Vin_max is mentioned in the excel sheet image above; I am curious, Is the VIN_max in your excel sheet is correct?.

    Thanks,

    Nitya

  • 0 in reply to Nityanand Hegde
    TI__Expert 5490 points

    Hi Abhishek,

    Any update on this issue?. 

    Thanks,

    Nitya