How to decide R1 power dissipation on LM5117EVM

Genius 4220 points

Hi,

I'd like to ask about the R1 power dissipation value on LM5117EVM.

3.3Ω 1/8W resistor is used for R1 on LM5117EVM.

Why is the 1/8W resistor used for R1?

I think that the max power consumption at R1 will be approximately as follows.

(Vcc regulator current limit)^2×R1　= 0.042A×0.042A×3.9Ω＝7mW

So, we can use 1/16W resistor for R1, is it right?

or is there any other point we should care about?

Thanks

0 EricLee over 10 years ago

Some vendor had a 50V (most of time 75V though) limitation in the datasheet.

Regards,

0 Go over 10 years ago in reply to EricLee

Genius 4220 points

Hi, Eric

Thank you for your comment.

Does it mean that the R1 on LM5117EVM was chosen on the voltage rating point of view?

So, If the input voltage on my customer's board will be lower (12V), we can use lower power

dissipation resistor ( like 1/16W) for R!?

Thanks

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