DRV10975ZPWPR datasheet(21/57 Pages) TI1

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Clock

IPDclk

Drive

V W

W V

U V

V U

W U

U W

Current

Search the Minimum Time

IPDCurrThr

Minimum

Time

Permanent

Magnet Position

Saturation Position of the

Magnetic Field

Smallest

Inductance

DRV10975

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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.

Figure 12. IPD Function

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