9.1.1 Anti-Windup and Initialization

The PI Controller has maximum and minimum limits for its output so as to keep it within practical values. If a non-zero error signal persists for a long time, the Integral component of the controller keeps increasing and may reach a value limited by its bit width. This phenomenon is called integrator windup and has to be avoided to have proper dynamic response. The PI Controller IP has an automatic anti-windup function which limits integrator as soon as the PI Controller reaches saturation.

In certain applications like motor control, it is important to initialize the PI Controller to a proper value before enabling it. Initializing the PI to a good value avoids jerky operation. The IP block has an enable input to enable or disable the PI Controller. When disabled, the output will be equal to the init input and when enabled, the output is PI computed value.