DRV10983ZPWPR datasheet(32/58 Pages) TI1

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Ktc

Lock detect

Kt_low

Kt_high

BEMF2 = Kt × speed

BEMF1 = U – I × Rm

Lock detected if BEMF2 > U

DRV10983

SLVSCP6C – JULY 2014 – REVISED MAY 2016

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9.4.7.2 Lock1: Abnormal Speed

If motor is operating normally, the motor BEMF should always be less than output amplitude. The DRV10983

uses two methods of monitoring the BEMF in the system. The U phase current is monitored to maintain an

estimate of BEMF based on the setting for Rm[6:0]. In addition, the BEMF is estimated based on the operation

speed of the motor and the setting for Kt[6:0]. Figure 29 shows the method for using this information to detect a

lock condition. If motor BEMF is much higher than output amplitude for a certain period of time, tLCK_ETR, it means

the estimated speed is wrong, and the motor has gotten out of phase.

Figure 29. Lock Detection 1

9.4.7.3 Lock2: Abnormal Kt

For any given motor, the integrated value of BEMF during half of an electrical cycle is constant. It is determined

by motor velocity constant (KtPH) (see Figure 30). It is true regardless of whether the motor is running fast or

slow. This constant value is continuously monitored by calculation and used as criteria to determine the motor

lock condition. It is referred to as Ktc.

Based on the KtPH value programmed, create a range from Kt_low to Kt_high, if the Ktc goes beyond the range

for a certain period of time, tLCK_ETR, lock is detected. Kt_low and Kt_high are determined by KtLckThr[1:0] (see

Figure 31).

Figure 30. BEMF Integration

Figure 31. Abnormal Kt Lock Detect

DRV10983ZPWPR Datasheet(PDF) 32 Page - Texas Instruments