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DRV8845: Subject: DRV8845 - Only Motor 3 Not Working (1, 2 OK) - Seeking Debugging Help

ian lee
Prodigy 30 points
Part Number: DRV8845


Tool/software:

Hello Experts,

I am currently working on a project to drive three DC motors using the DRV8845 motor driver.

I am experiencing an issue where Motors 1 and 2 are functioning correctly, but Motor 3 is not working at all.

Here's a summary of my setup and what I've already checked:

  • Driver: DRV8845
  • Motor Type: Brushed DC motors(rated 0.89A)
  • Control Method: I'm controlling the motor direction by setting the PHASEx pin (for each motor) to HIGH/LOW via an MCU GPIO. I'm tying the I0x and I1x pins together and feeding a PWM signal to them to control the motor speed.
  • Power Supply (VM): 24V
  • VCC: 3.3V
  • VREF: Approximately 0.89V (derived from a voltage divider from VCC).

What I have already verified:

  1. PWM Output: I have confirmed that the correct PWM signal is being output from the MCU for Motor 3's control pin (I03/I13).
  2. nSLEEP Pin: The nSLEEP pin (Pin 11) is correctly set to HIGH, enabling the driver.
  3. DIR (PHASE) Pin: The PHASE3 pin (Pin 10) is receiving the correct HIGH/LOW direction signal from the MCU.

Regards,

  • 0
    TI__Guru 51045 points

    Hi Ian,

    Thank you for reaching out to us via this forum.

    ian lee said:

    I am experiencing an issue where Motors 1 and 2 are functioning correctly, but Motor 3 is not working at all.

    Here's a summary of my setup and what I've already checked:

    • Driver: DRV8845
    • Motor Type: Brushed DC motors(rated 0.89A)
    • Control Method: I'm controlling the motor direction by setting the PHASEx pin (for each motor) to HIGH/LOW via an MCU GPIO. I'm tying the I0x and I1x pins together and feeding a PWM signal to them to control the motor speed.
    • Power Supply (VM): 24V
    • VCC: 3.3V
    • VREF: Approximately 0.89V (derived from a voltage divider from VCC).

    Thanks for the details. These are in compliance with device functionality. No concerns.

    You may be enabling parallel mode for bridges 3 and 4 by leaving PHASE4 pin open, as shown in the schematic. To use bridge 3 by independently, connect PHASE4 to LOW or HIGH and I04, I14 to HIGH for bridge 4, output 0 current. You could wire bridges 3 & 4 in parallel and leverage increased drive capacity. I suspect this may be the reason why OUT#A,B was not working, could be because SENSE4 was also open. Please try PHASE4 to GND or HIGH - or you can go the parallel 3 and 4 route and follow the datasheet suggestions. 

    Regards, Murugavel