AN1946 datasheet(23/35 Pages) STMICROELECTRONICS

Part #	AN1946

Description	SENSORLESS BLDC MOTOR CONTROL AND BEMF SAMPLING METHODS WITH ST7MC

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

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AN1946

5.2.2 Sizing of Network of Voltage Reference

The voltage comparator of ST7MC needs a voltage reference corresponding to the potential

of motor phase winding common neutral point and equal to half of DC bus.

This voltage reference corresponds to the network sizing calculation on the motor phase

(2.1V).

Figure 23. Network for Voltage Reference

This voltage reference is built from the power converter DC bus to manage of any variation.

For the main application the DC bus is equal to 325V.

The voltage divider allows the voltage to pass from the DC bus (325V) to the determined

voltage reference (2.1V).

This voltage adaptation is made with R10 & R11 resistors.

R10 = 180K and R11 = 1.2K giving

MCVREF = 2.15V

If we have a stable DC bus, the internal voltage reference of ST7MC can be used and in this

case is set to 2V.

MCVREF

VDC

AN1946 Datasheet(PDF) 23 Page - STMicroelectronics