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2.4 Speed Adjust Potentiometer (R6)
The speed-adjust potentiometer Spd_Adj can be found in Figure 4. The potentiometer adjusts the duty
cycle of the PWM signal which, will in turn, adjust the speed of the motor. In order to lower the duty cycle,
and in turn, lower the speed, turn the potentiometer clockwise. In order to increase the duty cycle, and in
turn, increase the speed, turn the potentiometer counter-clockwise.
Figure 4. DRV11873 Speed-Adjust Potentiometer
The onboard PWM signal for the DRV11873 is generated by a circuit based upon TI's TLC555 Low Power
Timer. It is capable of an approximately 25-kHz output that can be adjusted from 5% to 95% duty cycle.
This square output signal will switch from 0 V to 5 V.
In order to provide an external PWM signal to the DRV11873, first remove the 0.0-Ω resistor, R5.
Next, connect the external PWM signal to the PWM surface mounted test point. For more information
on the PWM input required by the DRV11873 please refer to the datasheet.
6
DRV11873 Evaluation Module SLWU083A–February 2013–Revised April 2013
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