ZHCSWR1H December 2009 – July 2024 DRV8412
PRODUCTION DATA
For optimal performance, the sense resistor must be:
The power dissipated by the sense resistor equals IRMS2 x R. For example, if peak motor current is 3A, RMS motor current is 2A, and a 0.05? sense resistor is used, the resistor will dissipate 2A2 × 0.05? = 0.2W. The power increases quickly with higher current levels.
Resistors typically have a rated power within some ambient temperature range, along with a de-rated power curve for high ambient temperatures. When a PCB is shared with other components generating heat, margin should be added. Always measure the actual sense resistor temperature in a final system, along with the power MOSFETs, as those are often the hottest components.
Because power resistors are larger and more expensive than standard resistors, use multiple standard resistors in parallel, between the sense node and ground. This distributes the current and heat dissipation.