1 Introduction

Optimal power consumption and heat dissipation in stepper motor drivers is important due to high motor current values. The shape of motor current in a stepper is determined by the applied voltage, speed of operation, and the motor parameters like resistance and inductance. Generally, a stepper motor works in the STEP/DIR interface with each pulse corresponding to the next step. Proper current regulation is required at every step to provide enough torque to drive the load, avoid a stall condition, and make sure that no missed steps occur. Hence, a fixed current value is determined at each step for current regulation as a percentage of full-scale current. To obtain maximum torque output from the motor, a stepper needs to be run at the maximum current value possible. This value can be limited by the stepper motor or the minimum overcurrent protection (OCP) value of the driver as specified in the data sheet. However, this causes thermal challenges in applications such as PLCs and textiles where a compact, dense PCB contains multiple motor driver ICs running simultaneously.

In many end applications, stepper motors do not require constant running operation. Steppers are used for accurate position control where the motor follows a rotate-stop-rotate pattern. During this stop condition, the motor does not move and is said to be in the holding position. During this time, the motor requires minimum torque output to maintain position. If the motor current value is reduced during this state, the device consumes significantly less power and leads to better system thermal performance.