SLVAFF1 January 2023 DRV8452 , DRV8462
PRODUCTION DATA
The Auto-torque algorithm implemented in the DRV8462, DRV8452 and DRV8461 motor drivers improves system efficiency by dynamically changing the output current according to the load torque. Whenever the load torque is low, the output current is lowered to reduce resistive losses; and when the load torque goes up, the output current increases immediately to prevent motor step loss. This concept is shown in Figure 2-1. As a result of improved efficiency due to auto-torque, the system runs at a lower temperature, which extends the lifetime of the components. Auto-torque can also enable the use of cheaper and smaller sized stepper motors.
In a stepper motor system, the total power delivered by the power supply goes into providing for the torque requirement of the load and into power losses such as resistive losses caused by motor winding resistance and driver ON resistance. This is represented by Equation 2:
where τ is load torque and ω is motor speed.
From Equation 2, it is observed that when the load torque increases, the power delivered by the supply increases as well. The auto-torque algorithm obtains information about the load-torque by monitoring the power delivered by the supply. The constant losses are represented by the ATQ_LRN parameter, and the ATQ_CNT parameter represents the power required to support the load torque, as explained in Section 2.1.