BRUSHLESS DC MOTOR CONTROLLER
FSP33035
Three Phase Closed Loop Controller
The FSP33035, by itself, is only capable of open loop motor speed control. For closed loop motor speed control, the
FSP33035 requires an input voltage proportional to the motor speed. Traditionally, this has been accomplished by
means of a tachometer to generate the motor speed feedback voltage. Figure below shows an application whereby
an MC33039, powered from the 6.25 V reference (Pin 8) of the FSP33035, is used to generate the required
feedback voltage without the need of a costly tachometer. The same Hall sensor signals used by the FSP33035 for
rotor position decoding are utilized by the MC33039. Every positive or negative going transition of the Hall sensor
signals on any of the sensor lines causes the MC33039 to produce an output pulse of defined amplitude and time
duration, as determined by the external resistor R1 and capacitor C1. The output train of pulses at Pin 5 of the
MC33039 are integrated by the error amplifier of the FSP33035 configured as an integrator to produce a DC
voltage level which is proportional to the motor speed. This speed proportional voltage establishes the PWM
reference level at Pin 13 of the FSP33035 motor controller and closes the feedback loop. The FSP33035 outputs
drive a TMOS power MOSFET 3–phase bridge. High currents can be expected during conditions of start–up,
breaking, and change of direction of the motor. The system shown in the below Figure is designed for a motor
having 120/240 degrees Hall sensor electrical phasing. The system can easily be modified to accommodate 60/300
degree Hall sensor electrical phasing by removing the jumper (J2) at Pin 22 of the FSP33035.
Closed Loop Brushless DC Motor Control Using the FSP33035 and MC33039
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2007-3-16
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