DRV10975_15 Datasheet, PDF (21/57 Pages) Texas Instruments – DRV10975 12-V, Three-Phase, Sensorless BLDC Motor Driver

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DRV10975
SLVSCP2 – JANUARY 2015
9.4.3.5 Motor Initialization
9.4.3.5.1 Align
DRV10975 aligns a motor by injecting dc current through a particular phase pattern which is current flowing into
phase V, flowing out from phase W for a certain time (configured by AlignTime[2:0]). The current magnitude is
determined by OpenLCurr[1:0]. The motor should be aligned at the known position.
The time of align affects the start-up timing (refer to Start-Up Timing). A bigger inertial motor requires longer align
time.
9.4.3.5.2 IPD
The inductive sense method is used to determine the initial position of the motor when IPD is enabled. IPD is
enabled by selecting IPDCurrThr[3:0] to any value other than 0000.
IPD can be used in applications where reverse rotation of the motor is unacceptable. Because IPD does not
need to wait for the motor to align with the commutation, it can allow for a faster motor start sequence. IPD works
well when the inductance of the motor varies as a function of position. Because it works by pulsing current to the
motor, it can generate acoustics which must be taken into account when determining the best start method for a
particular application.
9.4.3.5.2.1 IPD Operation
The IPD operates by sequentially applying voltage across two of the three motor phases according to the
following sequence: VW WV UV VU WU UW (see Figure 12). When the current reaches the threshold configured
in IPDCurrThr[3:0], the voltage across the motor is stopped. The DRV10975 measures the time it takes from
when the voltage is applied until the current threshold is reached. The time varies as a function of the inductance
in the motor windings. The state with the shortest time represents the state with the minimum inductance. The
minimum inductance is because of the alignment of the north pole of the motor with this particular driving state.
Clock
Drive
Current
IPDclk
VW
WV
UV
VU
WU
UW
U
N
V
S
W
IPDCurrThr
Search the Minimum Time
Permanent
Magnet Position
Saturation Position of the
Magnetic Field
Smallest
Inductance
Figure 12. IPD Function
Minimum
Time
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