Steps to select current sense resistor

step one.

 

Select the required resistance value in the loop.

 

Step two.

 

The accuracy required for selecting the resistance value is the minimum error value.

 

Step 3.

 

Confirm that the maximum current of the component that flows in the loop.

 

Step 4.

 

Calculate the minimum rated power required for the first year with this current, and its value must be greater than the actual use value when selecting this component.

 

Step 5.

 

Choose the required size according to the design space.

 

Step 6.

 

Is there a consideration of thermal electromotive force (EMF).

 

Example:

 

A design engineer must use Current Sensing Resistors (CSR) for the back-end OCP protection of the power supply. It needs to use 5mΩ due to the circuit design and the sensitivity of the power management IC used. The allowable resistance error is small, so it is necessary to select a resistance accuracy with an error of less than 1%. In addition, its regular current is about 15A. Therefore, the power consumption required to calculate the resistance is P=1.125W. The power supply has a small design space, so it must Choose a smaller size such as 1206 size, and this system generally does not consider the EMF effect, so the final model is selected as LMF1206M1WFR005.