MLX81200 Datasheet, PDF (5/15 Pages) Melexis Microelectronic Systems – BLDC Motor Controller

MLX81200
BLDC Motor Controller
2. Application Examples
The following sections show typical application examples¹.
2.1 BLDC Motor Control
In this sample application the IC can realize the sensor less driving of a BLDC motor via three external
power N-FET half bridges. The high side N-FET driving is done with a bootstrap output stage. The motor
speed command can be sent to an SW-pin, for example as duty cycle percentage. In this case SW4 can be
configured as timer input and the motor speed is a function of the duty cycle of the speed command signal.
The rotor position can be estimated based on motor currents at stand-still and very low speeds and by
sensing the back EMF voltage during short periods of time when the current through a phase is zero. The
motor phases can be driven with sinusoidal or trapezoidal currents. In the principle application schematic of
figure 2, the motor star point is not available. Instead it is modelled with external resistors from the motor
phases and connected to T input.
Motor current is controlled with an external shunt resistor and a fast internal comparator. The comparator
threshold is programmable with an 8-bit digital-to-analogue converter. In case of over current the bridge will
be switched off. The motor current can also be measured by the 10-bit ADC converter. Reverse polarity
protection of the bridge is realized with an external power FET connected to the ground line.
1 _{The application examples are principal application schematics only. The details need to be worked out for}
each application schematic separately, depending on the application requirements.
MLX81200 Product Abstract
Page 5 of 15
June/2012
Rev 2.4