DRV10987 Datasheet, PDF (14/69 Pages) Texas Instruments – DRV10987 12- to 24-V, Three-Phase, Sensorless BLDC Motor Driver

DRV10987
SLVSE89 – AUGUST 2017
Feature Description (continued)
PWM in
Analog
I²C
PWM duty
ADC
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Speed
Command
AVS,
Acceleration Current Limit
Closed Loop Accelerate
PWM_
DCO
Motor
Output
Amplitude
X
VCC
Figure 5. Multiplexing the Speed Command to the Output Amplitude Applied to the Motor
The output voltage amplitude applied to the motor is developed through sine wave modulation so that the phase-
to-phase voltage is sinusoidal.
When any phase is measured with respect to ground, the waveform is sinusoidally coupled with third-order
harmonics. This encoding technique permits one phase to be held at ground while the other two phases are
pulse-width modulated. Figure 6 and Figure 7 show the sinusoidal encoding technique used in the DRV10987
device.
PWM Output
Average Value
Figure 6. PWM Output and the Average Value
U-V
U
V-W
V
W-U
W
Sinusoidal Voltage From Phase to Phase
Sinusoidal Voltage With Third-Order Harmonics
From Phase to GND
Figure 7. Representing Sinusoidal Voltages With Third-Order Harmonic Output
The output amplitude is determined by the magnitude of V_CC and the PWM duty cycle output (PWM_DCO). The
PWM_DCO represents the peak duty cycle that is applied in one electrical cycle. The maximum amplitude is
reached when PWM_DCO is at 100%. The peak output amplitude is V_CC. When the PWM_DCO is at 50%, the
peak amplitude is V_CC / 2 (see Figure 8).
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