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# LMG3411R150: LMG3411EVM-031 covered wattage

Part Number: LMG3411R150
Other Parts Discussed in Thread: LMG3411EVM-031,

Hi All,

How much Wattage can the LMG3411EVM-031 cover with a normal LLC at a normal frequency?

• Hello,

The wattage that it covers really depends on the frequency, transformer design, input and output voltage of the LLC converter. I suggest that a simple calculation is conducted on this EVM. For this board, from junction to air, it has around 16C/W of thermal resistance (www.ti.com/.../snoaa14a.pdf), and you can calculate the allowable loss according to this data, and see at this loss, how much current the LLC that you want design can handle.

Thanks and regards,
Lixing
• Hi Lixing-san,

I can not open the pdf (www.ti.com/.../snoaa14a.pdf), so I can not understand.

• Hi Doi-san,

http://www.ti.com/lit/an/snoaa14a/snoaa14a.pdf

Thanks,

Lixing

• Hi Lixing-san,

I'm looking the Table 4 of this pdf.

It looks like Rθj-a is 16.4degC/W.

And 2-oz copper is not available normally.

If my customer use 1-oz copper board, 500W LLC can be achieved without FAN?

• Hello Doi-san,

With 500W LLC design, you are probably look into <2W of loss per GaN device. Therefore, I don't think it is a major challenge without fan when using GaN. I suggest the customer to have an estimated loss, and also provide their ambient temp, heat sink to ambient thermal resistance. These are all factors to affect their final performance and we can better support upon this information.

Thanks and regards,
Lixing
• Hi Lixing-san,

Thank you,
But I'm asking Rθj-a by using 1-oz copper board.
I think it is different from 2-oz Rθj-a.
Can you calculate?
• Hi Doi-san,

Could you please let me know the basic loss of your devices, ambient temp, heat sink to ambient thermal resistance? Heat dissipation involves a lot of components, which are not only PCB. Without these data given, I can only tell that according to my experience, you can do that.

Thanks and regards,
Lixing
• Hi Lixing-san,

As you know LMG3411R150 is just product folder made.
500W LLC is just only Planning stage. I don't know the specs of next stage LLC IC UCC256xx.
So I can not tell you about you want.
If Rθj-a by using 1-oz copper board is unknown, I can not recommend this for my customer.
• Hello Doi-san,

My answer to the customer is, if designed properly when selecting heat sinks, I believe it is not a challenge to have a 500W LLC design. The loss at 500W is very small. Even with 1-oz copper, the thermal resistance won't exceed 20C/W in the typical case. Therefore, there is still sufficient margin in the design. But in terms of detailed calculate, if you need it, I will need the info I mentioned above. Hope you can understand that. Thank you again!

Best regards,
Lixing
• Lixing-san,