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LM5030: Floating VIN pin and Connecting 12V input directly to VCC pin.

Part Number: LM5030

Hi,

We are designing a 100 Watt Push-Pull converter using LM5030. The input to the system is a 12Volt DC supply.

 

1.Recommended operating range of VCC and the ability to float VIN pin

Is it possible to connect 12V directly to the VCC pin of LM5030? At the same time by making the VIN pin of LM5030 to float.

2.Supply current limit of VCC and Power dissipation of LM5030 

The maximum current limit for the VCC of LM5030 is listed as typically 17mA.

If VCC is powered with 12V then the power dissipation of LM5030 is given by (12-7.7)*0.017 = 73mWatt.

Does the above calculation is correct?

 


Thanks and regards
DEEPAK V

  • Hi Deepak,

    Thank you for your interest in LM5030. What you can do is connect both Vin and VCC to an external bias rail (your 12V input). You will still want to connect a decoupling cap to the Vin and VCC pins. When this is done, the internal VCC regulator is disabled and the IC package will not dissipate as much power. Your power dissipation in the controller will depend on the gate drive current, your switching frequency, etc.

    Best Regards,
    Ben Lough
  • Hi Ben Lough,

    Thank you for the reply. We will follow as you suggested.

    But still some doubts persist in my mind.
    If I leave VIN pin as floating and connect 12V directly to VCC ,then will LM5030 work as expected ?
    What is the additional benifits we will have if we connect both VCC and VIN pin to 12V input rail ?

    Thanks and regards
    DEEPAK V
  • Hi Deepak,

    If you leave the Vin pin floating, the device will not work as expected. The primary benefit of using an external VCC is reduced power dissipation in the IC package.

    Best Regards,
    Ben Lough
  • Hi Ben Lough,

    Ok! now i am clear about it and we will follow as you suggested.
    Thanks once again for helping us out.


    Thanks and regards
    DEEPAK V