DRV10987 Datasheet, PDF (13/69 Pages) Texas Instruments – DRV10987 12- to 24-V, Three-Phase, Sensorless BLDC Motor Driver

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DRV10987
SLVSE89 – AUGUST 2017
Feature Description (continued)
8.3.2.4 Lock
When the motor is blocked or stopped by an external force, lock protection is triggered, and the device stops
driving the motor immediately. After the lock release time t_{LOCK_OFF}, the DRV10987 device resumes driving the
motor again. If the lock condition is still present, it enters the next lock protection cycle, and repeats until the lock
condition is removed. With this lock protection, the motor and device do not overheat or become damaged due to
the motor being locked (see Lock Detect and Fault Handling ).
During a lock condition the Status register indicates which of the locks has occurred.
8.3.3 Motor Speed Control
The DRV10987 device offers four methods for indirectly controlling the speed of the motor by adjusting the
output voltage amplitude. This can be accomplished by varying the supply voltage (V_CC) or by controlling the
speed command. The speed command can be controlled in one of three ways. The user can set the speed
command by adjusting either the PWM input (PWM in) or the analog input (Analog) or by writing the speed
command directly through the I²C serial port (I²C). The speed command is used to determine the PWM duty
cycle output (PWM_DCO) (see Figure 5).
The PWM input (PWM in) can have a minimum duty cycle limit applied. DutyCycleLimit[1:0], accessible through
the I²C interface, allows the user to configure the minimum duty cycle behavior. This behavior is illustrated in
Figure 4.
Output Duty
Cycle (%)
DutyCycleLimit[1:0], Reg0x95
00 - linear down to 5%, then holds at 5% until
duty command is 1.5 %; 0 % for duty command
below 1.5 %.
01 - linear down to 10%, then holds at 10% until
duty command is 1.5 %; 0 % for duty command
below 1.5 %.
Output Duty
Cycle (%)
100
DutyCycleLimit[1:0], Reg0x95
10 - linear down to 5%, then holds at 5% until
duty command is 1.5 %; 100 % for duty command
below 1.5 %.
11 - linear down to 10%, then holds at 10% until
duty command is 1.5 %; 100 % for duty command
below 1.5 %.
10
5
0
0 1.5 5 10
10
5
Input Duty Cycle
Input Duty Cycle (%)
0
0 1.5 5 10
Figure 4. Duty Cycle Profile
Input Duty Cycle (%)
The speed command may not always be equal to the PWM_DCO because the DRV10987 device has the AVS
function (see Anti-Voltage Surge Function), the acceleration current-limit function (see Acceleration Current
Limit), and the closed-loop accelerate function (see Closed-Loop Accelerate) to optimize the control
performance. These functions can limit the PWM_DCO, which affects the output amplitude (see Figure 5).
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