# SMD Resistor voltage rating

1. ## SMD Resistor voltage rating

Hi,

I'm trying to analyze the voltage parameter for a SMD resistor..

I need some advice from electronics experts..

Part number is RK73H1ETTP22R0F
Description :- RES THK FLM 0402 22ohm 1% 100ppm 0.063W (datasheet attached)
This part is rated for 50V.. ( it is specified for a resistance range from10Ω to 1MΩ )

I'm using it in series on data lines between DDR & Microcontroller it is operating at 1.8V logic..

My question is whether the part will still have a 50V rating in this application?

I ve read in a technical note saying we need to consider E=√P*R in selecting a resistor.. if that criteria applies.. then the above part Voltage rating will come to 1.8V..

E=√P*R =√[(1.8˛/22)*22] =1.8V

Does we need to calculate like that for all SMD resistor applications? or..is this calculation is required to be considered only for high voltage application (like 230VAC perhaps) ..

Thanks for any help,

•

2. ## Re: SMD Resistor voltage rating

I believe that P is the Rated Power of the resistor (in this case 0.063W), not the actual in-circuit dissipation as you have calculated. Besides, if you actually put 1.8V across the 22Ω resistor, you are well over the resistor's power rating.

Unfortunately, that makes your situation worse.

The notes that I have read all say something similar. That is, derate the resistor for lower than top-value resistance.

Rated voltage=√(Power Rating×Resistance value) or Max. working voltage, whichever is lower.

•

3. ## Re: SMD Resistor voltage rating

Thank you for pointing out..P is actually the rated power.. :)

--[[ ]]--