R52 = feedback resistor
R16 = input side resistor
Figure 3-7. Current Sense and Reference Generation Circuit
3.2.4.
BEMF, DC Bus Sense
Back-EMF generated in the phase windings can be determined from the voltage read at the individual
phase terminals. A schematic drawing for the voltage scaling and the filter circuit is shown in the figure
below. BEMF output is connected to the ADC and analog comparator of the MCU. Motor DC supply is
divided by network R79, R80 and connected to ADC reference and analog comparator.
Figure 3-8. Back-EMF, DC Bus Voltage Sense Circuit
3.2.5.
Over-voltage Protection (OVP)
DC bus voltage is monitored by the voltage sense circuit. If the voltage gets higher than 30VDC, the over-
voltage protection will shut down the FET driver. The OVP circuit is shown in the figure below. Sense
voltage is determined by the zener diode (D7) voltage (28V) and R-network R117 and R118. Vgs
(threshold) of Q8A is typically 2V.
Atmel ATSAMD21BLDC24V-STK [USER GUIDE]
Atmel-42681A-SMART-ARM-based-Motor-Control-Kit_User Guide-02/2016
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