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DRV8706H-Q1EVM: Is this driver the right guess for this Brush DC Motor?

Joaquim Rubio
Prodigy 10 points
Part Number: DRV8706H-Q1EVM
Other Parts Discussed in Thread: DRV8245-Q1, DRV8145-Q1
We need to mount a setup to validate one Matlab application which will be running in a Speedgoat, this application will give the % power that we need to apply to the motor.
This model will update the % of power every 1ms. Furthermore, the motor will have an incremental quadrature encoder attached to the shaft. The output of this angular sensor will be sent to the Motor Driving Model that will decide based on the angular position which torque to apply (Voltage Output between 0V and 10V). Finally, the motor driver will apply the torque based on the voltage measured in one of the AI of the Speedgoat.
The motor that we have is a one-axis Brushed DC motor (specs and more info of the system attached at the end). We would like to use one motor driver which will receive one analog signal (0V to 10V, which linearly relates to the % power to apply to the motor) from the Speedgoat.
As the motor has a very low inductance specification plus low voltage specification (the application field is the automotive, so the output voltage of the Amplifier should be 12V), Is this Motor Driver compliant as much as possible with the motor we selected. If you have other driver ideas, we would appreciate your point of view.
  • 0
    TI__Mastermind 23025 points

    Hi Joaquim,

    Thanks for reaching out to us via this forum. Based on the motor specs the peak current could be 30.5 A @ 10 V. This is typical of high torque BDC motors. Peak current occurs at startup inrush and while the motor is stalled. Another area to focus with is mechanical back driving of the BDC motor for example a tailgate application where the user slams the door forcing the motor to generate a voltage (like a dynamo) which will be conducted to the supply voltage via the output power MOSFET body diodes.

    The DRV8706H-Q1 is a good option as a gate driver with external MOSFETs and is suitable for 12 V operation. There is an S version with SPI control, DRV8706S-Q1 with more granular diagnostics and feedback on device status. We also have fully integrated solutions such as the DRV8245-Q1 also available in H- hardware and S/P- software control options, https://www.ti.com/lit/ds/symlink/drv8245-q1.pdf. For higher currents you may consider using 2x DRV8145-Q1 option, https://www.ti.com/lit/ds/symlink/drv8145-q1.pdf. These products have an associated Excel based a die thermal estimation calculator that can be downloaded from the product page and used for estimating whether it will run at a safe operating temperature for your motor. https://www.ti.com/tool/download/SLVRBI3 and  https://www.ti.com/tool/download/SLVRBN2 respectively. These are suitable for 12 V operation.

    I hope this helps. Let us know if further questions.  

    Regards, Murugavel

  • 0 in reply to Murugavel4637
    Prodigy 10 points

    Hello Murugavel,

    Thanks for your answer. I would have an additional question.

    For our setup, we will have one RTOS model giving the % of power every 1ms running in one speedgoat. This % of power (signal from 0V to 10V) will be the input of the motor driver to control the motor torque. Is it possible to use only the power stage of the board? I mean, Is it possible to send the % of power (in one voltage signal from 0V to 10V) to the driver board and that the board translates this value to one controll signal to the 12V Brush DC motor?

    I have seen that there are options controlling the motor with the TI GUI through the MCU or in some models through SPI, but with an Analog Voltage level?

    Kind regards.

  • 0 in reply to Joaquim Rubio
    TI__Mastermind 23025 points

    Hello Joaquim,

    The speed or the effective voltage across the DC motor is controlled by varying the duty cycle of a PWM input to control the bridge usually ~ 20 kHz. This is the generally adopted electronic speed control mechanism in the industry because the output stage losses are minimized with this approach. So you will need a translator like an MCU with ADC that accepts the 0 to 10 V analog voltage input and translates that to 0 to 100 % duty cycle of a PWM output that will be used for driving the motor driver whether a DRV8706H/S-Q1 or a DRV8245H/S-Q1.

    In our EVMs the GUI sends inputs to an onboard MCU that converts the slider value to a PWM duty cycle output to drive the DRV device.

    Regards, Murugavel