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LM3150: LM3150 chip temperature increase too much with output voltage increase

Part Number: LM3150
Other Parts Discussed in Thread: CSD18563Q5A, LM25145

Hi,

I am uisng LM3150, so far it is good. But I am curious one thing for chip temperature.

Test setting is: 24V input, wihout loading, with the different output voltage.

The question is that, why the chip temperature is so higher with over 10V and without loading?  With higher output voltage, and the chip temperaure increase too much?

Best Regards,

Kent

  • Hi Kent,

    The IC dissipation is the quiescent current (3.5mA) plus the gate drive current (Qg*Fsw for each FET). The total current times Vin (24V) is the power dissipation. 

    Here are some recommendations:

    1. No need for a 100V FET here, which is quite capacitive. Try the CSD18563Q5A, which is a good general-purpose FET in the same package. Qg at Vgs = 6V is only 10nC (compared to 23nC for the CSD19531). You can use this FET for the high-side as well.
    2. To optimize thermal performance, check that the IC (DAP (thermal pad) is connected by numerous vias the the PCB ground plane.
    3. Check the inducotr ripple current and related core loss as the ripple current reaches a max a Vout = Vin/2. High core loss may exist at no load, increase the overall board temperature.

    PS: the LM25145 is now our preferred 42V controller, giving better performance and lower cost relative to the LM3150.

    Regards,

    Tim