DRV10964 Datasheet, PDF (11/27 Pages) Texas Instruments – Three-Phase Sinusoidal Sensorless BLDC Motor Driver

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DRV10964
SLDS227 – MARCH 2016
No motor
Frequency Overflow
BEMF abnormal
Accelerate abnormal
Tri-state
and Restart
Logic
Speed abnormal
Figure 8. Lock Detect
The behavior of each lock detect scheme is described in the following sections.
7.3.5.1 Lock0: No Motor
The Phase U current is checked after transitioning from open loop to closed loop. If Phase U current is not
greater than 50mA then the motor is not connected. This is reported as a locked condition.
7.3.5.2 Lock1: Frequency Overflow
For most applications the maximum electrical frequency of the motor will be less than 3 kHz. If the motor is
stopped then the BEMF voltage will be zero. Under this condition, when the DRV10964 device is in the closed
loop mode, the sensor less control algorithm will continue to accelerate the electrical commutation rate even
though the motor is not spinning. A lock condition is triggered if the electrical frequency exceeds 3 kHz.
7.3.5.3 Lock2: BEMF Abnormal
For any specific motor, the integrated value of BEMF during half of an electrical cycle will be a constant as
illustrated by the shaded green area in Figure 9. This is true regardless of whether the motor runs fast or slow.
The DRV10964 monitors this value and uses it as a criterion to determine if the motor is in a lock condition.
The DRV10964 uses the integrated BEMF to determine the Kt value of the motor during the initial motor start.
Based on this measurement a range of acceptable Kt values is established. This range is between 1/2 x Kt and 4
x Kt During closed loop motor operation the Ktc value is continuously updated. If the calculated Ktc goes beyond
the acceptable range a lock condition is triggered. This is illustrated in Figure 10.
Figure 9. BEMF Integration
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