JAJSKK7 November 2021 DRV8231
PRODUCTION DATA
For optimal performance, the sense resistor must have the following characteristics:
The power dissipated by the sense resistor equals (IAVG)2 × R. For example, if peak motor current is 3 A, average motor current is 1.5 A, and a 0.2-Ω sense resistor is used, the resistor dissipates 1.5 A2 × 0.2 Ω = 0.45 W. The power quickly increases with higher current levels.
Resistors typically have a rated power within some ambient temperature range, along with a derated power curve for high ambient temperatures. When a PCB is shared with other components generating heat, the system designer should add margin. Measuring the actual sense resistor temperature in a final system is always best.
Because power resistors are larger and more expensive than standard resistors, using multiple standard resistors in parallel, between the sense node and ground, is common and distributes the current and heat dissipation.