DRV10975ZPWPR datasheet(29/57 Pages) TI1

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ILIMIT

ULIMIT

BEMF = Kt

speed

DRV10975

www.ti.com

SLVSCP2 – JANUARY 2015

Table 5. Configuring Commutation Advance Timing by Adjusting tSETTING (continued)

TCtrlAdv

tSETTING (µs)

HEX

tSETTING (µs)

HEX

tSETTING (µs)

HEX

[6:0]

0011011

480

1001100

4160

1111101

0011100

520

1001101

4480

1111110

0011101

560

1001110

4800

1111111

0011110

600

1001111

0011111

640

1011000

0101000

720

1011001

9.4.6 Current Limit

The DRV10975 has several current limit modes to help ensure optimal control of the motor and to ensure safe

operation. The various current limit modes are listed in Table 6. Acceleration current limit is used to provide a

means of controlling the amount of current delivered to the motor. This is useful when the system needs to limit

the amount of current pulled from the power supply during motor start-up. The lock detection current limit is a

configurable threshold that can be used to limit the current applied to the motor. Overcurrent protection is used to

protect the device; therefore, it cannot be disabled or configured to a different threshold. The current limit modes

are described in the following sections.

Table 6. DRV10975 Current Limit Modes

Current Limit Mode

Situation

Action

Fault Diagnose

Acceleration current limit

Motor start

Limit the output voltage amplitude

No fault

Lock detection current limit

Motor locked

Stop driving the motor and enter lock state

Mechanical rotation error

Overcurrent shutdown

Short circuit

Stop driving and recover when OC signal disappeared

Circuit connection

9.4.6.1 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 resistance, Rm, and programmed motor velocity constant, Kt, to limit the voltage applied to

the motor, U, as shown in Figure 25 and Equation 6.

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 25. Acceleration Current Limit

ULIMIT = ILIMIT × Rm + Speed × Kt

(6)

9.4.7 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 26 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.

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