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drv8412 and drv8432

Joel Zegarra
Prodigy 40 points

Hi, I have two brushed dc motors in series and the following link lists all the specifications.  I will be running two 19.1V motors at 24V max

 www.pittman-motors.com/.../14206-Brush-DC-Motor.aspx

I was hoping that this H bridge below would be able to help me 

www.ti.com/.../drv8412.pdf

I'm hoping to hook both of the motors (in series) in the parallel configuration shown in the data sheet but I'd like to know if that configuration will be able to handle the amperage that the motors will demand and if you could provide me with a data sheet solely  for the parallel configuration that'd be helpful.  

Also maybe theres a better driver to handle the 6A (say cascading two different H bridges maybe?) that the motor would require for continuous torque seeing as how I need just a driver to handle 24V I'd appreciate any feedback or ideas that could help in controlling the speed and rotation of the motor 

  • 0
    TI__Guru** 114905 points
    Hi Joel,

    The datasheet is written for the device in standard operation (non-parallel mode). In general, when the current is specified, it is doubled in parallel mode. Is there a specific question that you have about the datasheet?

    When you connect the motors in series, what current are you expecting to drive through the motors (peak and RMS)? This will allow us to provide alternate suggestions.
  • 0 in reply to Rick Duncan
    Prodigy 40 points

    Oh ok, so what you're saying is that because 6A is what the driver provides provides to the motors in normal operation, the parallel set up would provide 12A max to the motor, right?

    Im going to send  current that is coming from a DC power  source.  Also I do have a question about the datasheet.  The connection to the motor in parallel shows a wire going to pwm outA and  outB.  Is one end of the motor (positive lead) connectrd to OutA and the ground lead of the motor to OutzB?

  • 0 in reply to Joel Zegarra
    TI__Guru** 114905 points
    Hi Joel,

    So just to be clear, for the DRV8432 the datasheet states:
    DRV8432 (Power Pad Up): up to 2 × 7-A DRV841x2 Continuous Output Current (2 × 12-A Peak) in Dual Full-Bridge Mode or
    14-A Continuous Current in Parallel Mode (24-A Peak)

    This means each output pair can drive 7A continuous or if connected in parallel the two outputs can drive 14A continuous. These current values are based on proper heatsinking.

    Sorry, I am confused about your datasheet question. Are you looking at Figure 8 of the datasheet? If so, lthe answer is yes, one end of the motor is connected to OUTA and the other end is connected to OUTB.
  • 0 in reply to Rick Duncan
    Prodigy 40 points

    Im looking at figure 15.

    Im curious to know how the PWM signals work for the parallel connection. Do I send a pwm signal from the controller to PWMA while PWMB is off im order to turn the motor one way and viceversa to reverse the direction of the motor?

  • 0 in reply to Joel Zegarra
    TI__Guru** 114905 points

    Hi Joel,

    Thanks for confirming you are looking at figure 15. For parallel mode operation OUT_A and OUT_B are controlled by PWM_A. OUT_C and OUT_D are controlled by PWM_B.

    Please refer to page 15 of the datasheet:

    In parallel full bridge mode (mode 3), PWM_A controls both half bridges A and B, and PWM_B controls both half bridges C and D, while PWM_C and PWM_D pins are not used (recommended to connect to ground). Bridges A and B are synchronized internally (even during CBC), and so are bridges C and D. OUT_A and OUT_B should be connected together and OUT_C and OUT_D should be connected together after the output inductor or ferrite bead. If RESET_AB or RESET_CD are low, all four outputs become high-impedance. Figure 15 shows an example of parallel full bridge mode connection.


    Looking at figure 15, one end of the motor should be connected to OUT_A and OUT_B after the inductor / ferrite bead as shown. The other end should be connected to OUT_C and OUT_D after the inductor / ferrite bead.

  • 0 in reply to Rick Duncan
    Prodigy 40 points

    So do I send a PWM signal from the controller to PWM_A while PWM_B is off in order to turn the motor one way and vice versa to reverse the direction of the motor?

  • 0 in reply to Joel Zegarra
    TI__Guru** 114905 points

    Hi Joel,

    Yes, you do. It is preferred to use the term "logic low" instead of "off" when referring to PWM_B. "Logic low" means that input is driven to a low level.

    So, you would send the PWM signal to input PWM_A while setting PWM_B to a logic low. RESET_AB/ and RESET_CD/ will  both be set to a logic high.

    Please note the second to last sentence quote in the prior response for mode 3:  If RESET_AB or RESET_CD are low, all four outputs become high-impedance.