Circuit description

UM1996

18/29

DocID028716 Rev 2

4.3

BEMF detection circuit

The X-NUCLEO-IHM08M1 expansion board provides two hardware solutions for motor

and other based on sensorless detection.

In 6-step driving mode, one of the three phases is left in the high-impedance state and we

can detect BEMF zero-crossing events by comparing the voltage of this phase with the

center-tap voltage. This signal is acquired through an analog circuit embedded on the

board, as shown below.

Figure 17: X-NUCLEO-IHM08M1

– BEMF detection circuit

The X-NUCLEO-IHM08M1 expansion board provides the hardware for bus voltage sensing

and temperature measurement. This signal is acquired with a resistor divider and with an

embedded NTC (placed close to STL220N6F7 Power MOSFET), as shown below.

Figure 18: X-NUCLEO-IHM08M1

– VBUS and temperature sensing circuit