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DRV8412: Running the driver with 100% duty cycle

Joseph Burton
Prodigy 20 points
Part Number: DRV8412
Other Parts Discussed in Thread: DRV8870

Is it possible to run the DRV8412 with a 100% duty cycle input?  I have a design that uses a 24V motor.  When the PWM_A and PWM_B inputs are set to A as a constant high and B as a constant low, the OUT_A voltage reads at about 10V.  I changed the bootstrap capacitors to 1uF.  Figure 5 in the datasheet seems to indicate this is possible.  What other changes need to be made to allow for 100% duty cycle?

  • 0
    TI__Guru** 114905 points

    Hi John,

    Please refer to section 7.3.2.1 Bootstrap Capacitor Undervoltage Protection. 100% duty cycle will cause the device to initiate bootstrap capacitor recharge sequences. So 100% is not achievable. In many cases, using a very small recharge pulse of 50ns @ 10kHz will have minimal effect on the system while yielding 99.95 duty cycle.

    Figure 5 was intended to show that the duty cycle from input to output is maintained. This is not always the case. In some motor drivers like the DRV8870, internal synchronizers can affect the usable duty cycle.