DRV10987 Datasheet, PDF (31/69 Pages) Texas Instruments – DRV10987 12- to 24-V, Three-Phase, Sensorless BLDC Motor Driver

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Speed
Command
Maximum
Speed
Command
DRV10987
SLVSE89 – AUGUST 2017
PWM duty
0
100%
Figure 25. PWM-Mode Speed Command
8.4.6.4 I²C-Mode Speed Control
The DRV10987 device can also command the speed through the I²C serial interface. To enable this feature, the
OverRide bit is set to 1. When the DRV10987 device is configured to operate in I²C mode, it ignores the signal
applied to the SPEED pin.
The speed command can be set by writing the SpdCtrl[8:0] bits. The 9-bit SpdCtrl [8:0] located in the SpeedCtrl
registers is used to set the peak amplitude voltage applied to the motor. The maximum speed command is set
when SpdCtrl [8:0] is set to 0x1FF (511).
8.4.6.5 Closed-Loop Accelerate
To prevent sudden changes in the torque applied to the motor which could result in acoustic noise, the
DRV10987 device provides the option of limiting the maximum rate at which the speed command changes.
ClsLpAccel[2:0] can be programmed to set the maximum rate at which the speed command changes (shown in
Figure 26).
y%
Speed command
input
x%
Speed command
after closed loop
accelerate buffer
y%
x%
Closed loop
accelerate settings
Figure 26. Closed-Loop Accelerate
8.4.6.6 Control Coefficient
The DRV10987 device continuously measures the motor current and uses this information to control the drive
state of the motor when operating in closed-loop mode. In applications where noise makes it difficult to control
the commutation optimally, the CtrlCoef[1:0] can be used to attenuate the feedback used for closed-loop control.
The loop is less reactive to the noise on the feedback and provides for a smoother output.
8.4.6.7 Commutation Control Advance Angle
To achieve the best efficiency, it is often desirable to control the drive state of the motor so that the motor phase
current is aligned with the motor BEMF voltage.
To align the motor phase current with the motor BEMF voltage, consider the inductive effect of the motor. The
voltage applied to the motor should be applied in advance of the motor BEMF voltage (see Figure 27). The
DRV10987 device provides configuration bits for controlling the time (t_adv) between the driving voltage and
BEMF.
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