Current sense feedback is important in a motor system to implement closed-loop torque control or detect current limits. TI’s BLDC motor drivers can offer 1x, 2x, or 3x current sense amplifiers (CSAs) to sense the motor phase currents and provide as analog voltage feedback for a microcontroller’s analog-to-digital converter. There are two CSA architectures implemented in TI BLDC motor drivers: external shunt resistors and integrated low-side current sensing.

In external shunt resistor architectures, the motor current through an external shunt produces a proportional CSA output voltage. These are used mostly in gate driver architectures as the shunt resistors are rated for high power and are in the range of milliohms.

Integrated low-side current sensing architectures do not require an external shunt resistor; the motor current going into the low-side MOSFET is sensed and converted into an analog voltage using current mirroring technology. This form of current sensing is used mostly in integrated MOSFET BLDC motor drivers.