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Original question:

BQ24171: Functionality Clarification

BQ24171: Clarification in EVM

Akilarasan R
Prodigy 220 points
Part Number: BQ24171

In bq24171EVM, sense resistor(R2) of value 10 mohm with wattage of 0.5W is used. It was selected based on the input voltage (4.5V - 16V) and load current (5A) right?.

In our design, input voltage will be 12V , load current will be 3A max and we will be using 10 mohm. The calculated sense resistor wattage based on the formula P = I2R is  0.09 W.

My doubt is that I can use 0.25W sense resistor right?. Because sense resistor used in board has dimension of 0.200" L x 0.100" W (5.08mm x 2.54mm). It consumes lot of space. That's why we want it in smaller size with lesser wattage. 

Please clarify whether I can use 0.25W sense resistor or not?

  • 0
    TI__Guru*** 147715 points

    Hi Akilarasan,

    Yes but keep in mind that all resistors have a temperature coefficient.  Their resistance changes as the package gets hotter.  A larger footprint provides better heat sinking and so its resistance changes less.

    Regards,

    Jeff