Using the break function with other MCU resources

AN4277

14/23

DocID024409 Rev 2

5

Using the break function with other MCU resources

5.1

Break function used for over-current protection

The STM32F3 Series microcontroller embeds a set of peripherals designed to resolve

common motor control issues by reducing the number of required external components.

This section describes how to use these peripherals to implement over-current protection.

Figure 3 shows the over-current protection network that can be implemented using the

internal resources of the STM32F3 Series.

Figure 3. Over-current protection network implemented with STM32F3 Series

The principle of this over-current protection mechanism can be summarized as follows:

•

The phase current of the motor flows in the power transistor of the inverter bridge and

•

This voltage drop is compared with a threshold (V-) defining the maximum admissible

current.

•

If the threshold is exceeded, a break signal stops the PWM generation putting the

system in a safe state.

All of these actions can be performed using the internal resources of the STM32F3 Series

and, in particular, the embedded comparators and advanced timer break function (BRK2). In

the basic implementation, the only external component required is the shunt resistor that

must be sized depending on the current to be monitored and the shunt resistor power rating.