L6258EP_07 STMICROELECTRONICS [STMicroelectronics], L6258EP_07 Datasheet - Page 22

• Manufacturer Part Number: L6258EP_07
• Description: PWM controlled high current DMOS universal motor driver
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

PWM current control loop
3.5
22/32
Figure 8.
We can see that the effect of the load pole is cancelled by the zero of the Bx block ; the total
Aloop cross a the 0dB axis with a slope of -20dB/decade, having in this way a stable system
with an high gain at low frequency and a bandwidth of around 8KHz.
To increase the bandwidth of the system, we should increase the gain of the Bx block,
keeping the zero in the same position. In this way the result is a shift of the total Aloop
transfer function up to a greater value.
Effect of the Bemf on the current control loop stability
In order to evaluate what is the effect of the Bemf voltage of the stepper motor we have to
look at the load block:
Aloop bode plot (compensated)
L6258EP