Functional description
powerSTEP01
7.4.1
Automatic Full-step and Boost modes
When motor speed is greater than a programmable full-step speed threshold, the L6480
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 π/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).
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(π/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
V
peak
sin(π /4)x V
peak
Phase A
Phase B
Full-step
Microstepping
Microstepping
(2N+1) x π /4
(2N+1) x π /4
AM12829v1
24/90
DocID025022 Rev 1
STMICROELECTRONICS [ ST ]
