DRV10987 Datasheet, PDF (25/69 Pages) Texas Instruments – DRV10987 12- to 24-V, Three-Phase, Sensorless BLDC Motor Driver

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DRV10987
SLVSE89 – AUGUST 2017
Reverse drive is suitable for applications where the load condition is light at low speed and relatively constant
and where the reverse speed is low (for example, a fan motor with little friction). For other load conditions, the
motor brake function provides a method for helping force a motor which is spinning in the reverse direction to
stop spinning before the device initiates a normal start-up sequence.
8.4.3.4 Motor Brake
The motor brake function can be used to stop the spinning motor before attempting to start the motor. The brake
is applied by turning on all three of the low-side driver FETs.
Brake is enabled by configuring a non-zero BrkDoneThr[2:0]. Brake is applied for a time configured by
BrkDoneThr[2:0] (forward or reverse). After the motor is stopped, the motor position is unknown. To proceed with
restarting in the correct direction, the IPD or align-and-go algorithm must be implemented. The motor start
sequence is the same as it would be for a motor starting in the stationary condition.
The motor brake function can be disabled. The motor skips the brake state and attempts to spin the motor as if it
were stationary. If this happens while the motor is spinning in either direction, the start-up sequence may not be
successful.
8.4.3.5 Motor Initialization
8.4.3.5.1 Align
The DRV10987 device 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 (see Start-Up Timing). A bigger-inertia motor requires longer align
time.
8.4.3.5.2 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 is not
required 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.
8.4.3.5.2.1 IPD Operation
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 16). When the current reaches the threshold configured in
IPDCurrThr[3:0], the voltage across the motor is stopped. The DRV10987 device 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.
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