5 Maximum Resolution or Minimum Shunt Loss

Depending on how wide your current range is, you might have the option of optimizing your design for maximum resolution or for minimizing power dissipated across your shunt. The shunt resistor you choose will be the key factor for determining the resolution and shunt dissipation.

The calculated R_{SHUNT MAX} is the value needed for maximum resolution assuming the calculated value is also larger than R_{SHUNT MIN}. The value calculated may not be a standard value and therefore unavailable from part distributors or even manufacturers. Consequently, you will need to adjust your value to match what can practically be done. To get the max desired current within your measurement range with max measurement resolution, you will need to choose a resistor value smaller than what you calculated, preferably the nearest, affordable, normally stocked option you can find.

For minimizing the power dissipation across the shunt, you simply need to use a resistor value smaller than R_{SHUNT MAX}. The exact value chosen will be dependent upon what error is allowed at the minimum sense current, where the error is dominated by the input offset voltage. If you are able to calibrate out the device input offset voltage and use one of the larger conversion settings you may be able to choose a shunt value at or close to R_{SHUNT MIN}.