DRV10975ZPWPR datasheet(33/65 Pages) TI1

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ILIMIT

U_LIMIT

BEMF = Kt

Speed

DRV10975, DRV10975Z

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SLVSCP2E – JANUARY 2015 – REVISED MAY 2018

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8.4.6.1 Acceleration Current Limit

The acceleration current limit limits the voltage applied to the motor to prevent the current from exceeding the

programmed threshold. The acceleration current limit threshold is configured by writing the SWiLimitThr[3:0] bits

to select ILIMIT. The acceleration current limit does not use a direct measurement of current. It uses the

programmed motor phase resistance, RPH_CT, and programmed BEMF constant, Kt, to limit the voltage applied to

the motor, U, as shown in Figure 27 and Equation 7.

When the acceleration current limit is active, it does not stop the motor from spinning nor does it trigger a fault.

The acceleration current limit function is only available in closed loop control.

Figure 27. Acceleration Current Limit

ULIMIT = ILIMIT × RPH_CT + Speed × Kt

(7)

8.4.7 Lock Detect and Fault Handling

The DRV10975 provides several options for determining if the motor becomes locked as a result of some

external torque. Five lock detect schemes work together to ensure the lock condition is detected quickly and

reliably. Figure 28 shows the logic which integrates the various lock detect schemes. When a lock condition is

detected, the DRV10975 device takes action to prevent continuously driving the motor in order to prevent

damage to the system or the motor.

In addition to detecting if there is a locked motor condition, the DRV10975 also identifies and takes action if there

is no motor connected to the system.

Each of the five lock-detect schemes and the no motor detection can be disabled by respective register bits

LockEn[5:0].

When a lock condition is detected, the MtrLck in the Status register is set. The FaultCode register provides an

indication of which of the six different conditions was detected on Lock5 to Lock0. These bits are reset when the

motor restarts. The bits in the FaultCode register are set even if the lock detect scheme is disabled.

The DRV10975 reacts to either locked rotor or no motor connected conditions by putting the output drivers into a

high-impedance state. To prevent the energy in the motor from pumping the supply voltage, the DRV10975

incorporates an anti-voltage-surge (AVS) process whenever the output stages transition into the high-impedance

state. The AVS function is described in AVS Function. After entering the high-impedance state as a result of a

fault condition, the system tries to restart after tLOCK_OFF.

DRV10975ZPWPR Datasheet(PDF) 33 Page - Texas Instruments