POWERSTEP01 datasheet(24/92 Pages) STMICROELECTRONICS

24 / 92 page

Functional description

powerSTEP01

24/92

DocID025022 Rev 5

Automatic Full-step and Boost modes

When motor speed is greater than a programmable full-step speed threshold, the device

switches automatically to Full-step mode; the driving mode returns to microstepping when

motor speed decreases below the full-step speed threshold.

The switching between the microstepping and Full-step mode and vice-versa is always

performed at an electrical position multiple of

/4 (Figure 7 and Figure 8).

Full-step speed threshold is set through the related parameter in the FS_SPD register

(Section 11.1.9 on page 55).

When the BOOST_MODE bit of the FS_SPD register is low (default), the amplitude of the

voltage squarewave in Full-step mode is equal to the peak of the voltage sinewave

multiplied by sine(

/4) (Figure 7). This avoids the current drop between the two driving

modes.

When the BOOST_MODE bit of the FS_SPD register is high, the amplitude of the voltage

squarewave in Full-step mode is equal to the peak of the voltage sinewave (Figure 8). That

improves the output current increasing the maximum motor torque.

Figure 7. Automatic Full-step switching in Normal mode

Phase A

Phase B

(2N+1) x π /4

Full-step

Microstepping

peak

sin(π /4)x V

peak

AM12829v1

POWERSTEP01 Datasheet(PDF) 24 Page - STMicroelectronics