LM3478 - CSD17559Q5 very hot

Hello Krzysztof,

I will look at this on one of our eval boards and reply to you.

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Regards,

Graham

Attached files below.

boost.pdf

Hi Krzysztof,
Your schematic shows only a low capacitance on the Vin pin (100nF), this should be larger to avoid oscillation. I have put your values through our WebBench software and it calls for a 33uF cap on VIN. A 22uF inductor is also recommended. Can you try these components to see if there is an improvement in the heating on the board?

Hi,

The previous AD/DC stage has 3x2200uF. I have used WebBench with various work conditions and the result was that the inductor should be rather smaller than 10uH not larger. The input voltage can vary from 10V to 14.5V.

Hi Krzysztof,
10uF is shown when I put the lower Vin value in. Are your caps from the previous stage close to the 3478 device?
We do experience heating in the FET but this is usually controlled via the board design etc. as you have indicated. You may be able to reduce this heating by limiting the current by changing the Rsen resistor but I do not know what figures you used to arrive at the 6mOhm value you are using.