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LMG3622: Thermal resistance value

Kaji@PAN
Mastermind 7465 points
Part Number: LMG3622
Other Parts Discussed in Thread: UCC28782, LMG3616,

Tool/software:

Hello,

I am an FAE at a distributor that handles TI products, and I received the following inquiry from my customer.
My customer is using UCC28782 with LMG3622 and LMG3616.
LMG3622 is the main switch and LMG3616 is for active clamp.
However, the board area is small and both GaN FETs generate heat.
Because heat dissipation from the bottom side of the GaN FET is not expected, I would like to use thermally conductive resin to dissipate heat to a heat sink from the top.
I would like to select the thermal resistance (thickness and material) of the thermally conductive resin, so please tell me the RθJC(top) of both GaN FETs.

Best regards,

  • +1
    TI__Expert 3900 points

    Hello,

    Good question here. The thermal resistance for these devices is much lower on the bottom-side, so the best thermal solution would be placing heatsink on bottom-side of PCB. Thermal resistance through top of package will be quite high which is usually why we don't publish this value in the datasheet.
    However, in many applications, especially low power adapters, bottom-side heat sink is simply not feasible

    The solution you are proposing is very common for these low power applications, where a thermal glue or resin is placed between the top-side of GaN package and some heat spreader.

    The thermal resistance junction-to-case through the top case is 14.7 C/W.

    Hope this helps,
    Zach