DRV10987 Datasheet, PDF (42/69 Pages) Texas Instruments – DRV10987 12- to 24-V, Three-Phase, Sensorless BLDC Motor Driver

DRV10987
SLVSE89 – AUGUST 2017
www.ti.com
8.4.12.7 Speed-Command Readback
The DRV10987 device converts the various types of speed command into a speed command value (SpeedCmd)
as shown in Figure 40. By reading SpeedCmd, the user can observe PWM input duty (PWM digital mode),
analog voltage (analog mode), or I²C data (I²C mode). This value is calculated as shown in Equation 14.
Equation 14 shows how the speed command as a percentage can be calculated and set in SpeedCmd.
Duty_SPEED (%) = SpeedCmd × 100 / 255
where
• Duty_SPEED = Speed command as a percentage
• SpeedCmd = Register value
(14)
8.4.12.8 Speed-Command Buffer Readback
If acceleration current limit and AVS are enabled, the PWM duty cycle output (read back at spdCmdBuffer) may
not always match the input command (read back at SpeedCmd) shown in Figure 40. See Anti-Voltage Surge
Function and Current Limit.
By reading the value of spdCmdBuffer, the user can observe buffered speed command (output PWM duty cycle)
to the motor.
Equation 15 shows how the buffered speed is calculated.
Duty_OUTPUT (%) = spdCmdBuffer × 100 / 255
where
• Duty_OUTPUT = The maximum duty cycle of the output PWM, which represents the output amplitude in
percentage.
• spdCmdBuffer = Register value
(15)
PWM in
Analog
I²C
PWM duty
ADC
Speed
Command
SpeedCmd
spdCmdBuffer
AVS,
Acceleration Current Limit
Closed Loop Accelerate
PWM_DCO
Figure 40. SpeedCmd and spdCmdBuffer Registers
8.4.12.9 Fault Diagnostics
See Lock Detect and Fault Handling.
42
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