SLVSEE8B November 2019 – May 2021 DRV8899-Q1
The first step in configuring the device requires the desired motor speed and microstepping level. If the target application requires a constant speed, then a square wave with frequency ƒstep must be applied to the STEP pin. If the target motor speed is too high, the motor does not spin. Make sure that the motor can support the target speed. Use Equation 2 to calculate ƒstep for a desired motor speed (v), microstepping level (nm), and motor full step angle (θstep)
The value of θstep can be found in the stepper motor data sheet, or written on the motor.
For example, the motor in this adaptive headlight application is required to rotate at 15°/step for a target of 300 rpm at 1/8 microstep mode. Using Equation 2, ƒstep can be calculated as 960 Hz.
For the DRV8899-Q1 device, the microstepping level is set by the MICROSTEP_MODE bits in the SPI register and can be any of the settings listed in Table 8-2. Higher microstepping results in a smoother motor motion and less audible noise, but increases switching losses and requires a higher ƒstep to achieve the same motor speed.
|0000b||Full step (2-phase excitation) with 100% current|
|0001b||Full step (2-phase excitation) with 71% current|
|0010b||Non-circular 1/2 step|