DRV10975_15 Datasheet, PDF (23/57 Pages) Texas Instruments – DRV10975 12-V, Three-Phase, Sensorless BLDC Motor Driver

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DRV10975
SLVSCP2 – JANUARY 2015
Motor spinning direction
U
V
N
S
W
U
V
N
U
V
N
U
V
N
U
V
N
S
W
ÛDGYDQFH
S
S
W
W
Ûadvance
ÛDGYDQFH
Figure 15. IPD Advance Angle
S
W
ÛDGYDQFH
9.4.3.5.3 Motor Start
After it is determined that the motor is stationary and after completing the motor initialization with either align or
IPD, the DRV10975 begins to accelerate the motor. This acceleration is accomplished by applying a voltage
determined by the open loop current setting (OpenLCurr[1:0]) to the appropriate drive state and by increasing the
rate of commutation without regard to the motor's real position (referred to as open loop operation). The function
of the open loop operation is to drive the motor to a minimum speed so that the motor generates sufficient BEMF
to allow the commutation control logic to accurately drive the motor.
Table 4 lists the configuration options that can be set in register to optimize the initial motor acceleration stage
for different applications.
Table 4. Configuration Options for Controlling Open Loop Motor Start
Description
Open to closed loop threshold
Align time
First order accelerate
Second order accelerate
Open loop current setting
Open loop current ramping
Reg Name
SysOpt4
SysOpt4
SysOpt3
SysOpt3
SysOpt2
SysOpt2
ConfigBits
Op2ClsThr[4:0]
AlignTime[2:0]
StAccel[2:0]
StAccel2[2:0]
OpenLCurr[1:0]
OpLCurrRt[2:0]
Min Value
0.8 Hz
40 ms
0.3 Hz/s
0.22 Hz/s2
200 mA
0.23 VCC/s
Max Value
204.8 Hz
5.3 s
76 Hz/s
57 Hz/s2
1.6 A
6 VCC/s
9.4.3.6 Start-Up Timing
Start-up timing is determined by the align and accelerate time. The align time can be set by AlignTime[2:0], as
described in Register Definition. The accelerate time is defined by the open-to-closed loop threshold
Op2ClsThr[4:0] along with the first order StAccel[2:0](A1) and second order StAccel2[2:0](A2) accelerate rates.
Figure 16 shows the motor start-up process.
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