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DRV10975: No Output Voltage / Speed Command Buffer = 0

Part Number: DRV10975


I've been working with the DRV10975Z in attempts to drive a Maxon 351056. I have followed the quick start guide using i2c to manually write and read registers and speed with a Raspberry Pi Pico. It seems as though I can read & write eeprom and other registers correctly but no matter what I do, I cannot get the motor driver to produce voltage. I am not sure what is causing this issue but I have noticed that the Speed Command Buffer is always set to 0.

From the QSG, my motor parameters are:

  • MAXIMUM SPEED (RPM) - 9380
  • R (PHASE-CT) - 10 Ohms (Measured)
  • Kt (PHASEPHASE) - 71 mV/Hz
  • LR CONSTANT - Unknown for now
  • INERTIA - 5.1gcm^3

And I have set the following EEPROM addresses

  • Phase Resistance (0x20)
    • 0x7B
  • Kt (0x21)
    • 0x3D
  • Disable IPD (0x2A)
    • 0x0D
  • Disable ISD & Reverse Drive (0x23)
    • 0x0C
  • Set Align Time to 5.3s & O2C Loop at ~80Hz (0x26)
    • 0xB0
  • Set Accel Constants (0x25)
    • 0xFD
  • Set Open Loop Current & Disable Break (0x24)
    • 0x58
  • Disable Closed Loop (0x2B, 0x0D)

To Run the test I write the following commands:

  • Addr:0x03 --- 0x80 (Disable Sleep)
  • Addr:0x02 --- 0x81 (Enable i2c speed and MSB of Speed)
  • Addr:0x01 --- 0x2c ([8:0] Speed)

Effectively, I can see that the speed command changes on 0x1B but the speed command buffer on 0x1C is always 0. 

If I'm correct, the speed command buffer is the actual command?

I am using a custom PCB seen in the image below. Unfortunately it was designed for the DRV10975 and not DRV10975Z; however, it is my understanding that the Zener diode is not required unless you are utilizing sleep mode, which I will not. So it is possible that my issue is related to having the inductor instead of the resistor (currently on order). 


  • I have tested two motor driver ICs on two separate PCBs (Same results)
  • Attempted driving with analog command (Same results)
  • Tested continuity between output pins on IC and motor terminal
  • Verified impedance between all terminals and ground with motor disconnected
  • Run commands with two separate motors and with no motor connected.

Any help would be greatly appreciated!

Thank you,

Joseph Lupton

  • Hi Joseph,

    I'll get back to you shortly!



  • Joseph,

    Can you check how much current is drawn from the power supply when the motor is idle? If you see the current in mA then you should be good. If it is in uA, the the device is in sleep mode. Is the SPEED pin floating? Can you add Zener diode in your schematic as shown in below image? Also, can you disable Initial speed detect and see if this helps fix the issue?



  • Hi Vishnu,

    Thank you for the quick reply!

    I will check the motor current and get back to you on that tomorrow. Should I still be able to communicate with the device if it is in sleep mode?

    "8.3.4 Sleep or Standby Condition

    The DRV10975 is available in either a sleep mode or standby mode version. The DRV10975 enters either sleep or standby to conserve energy. When the device enters either sleep or standby, the motor stops driving. The step-down regulator is disabled in the sleep mode version to conserve more energy. The I 2C interface is disabled and any register data not stored in EEPROM will be reset. The step-down regulator remains active in the standby mode version. The register data is maintained, and the I 2C interface remains active"

    That last part is a little confusing.

    I will also disable ISD and the break. It looks like in an effort to disable them, I enabled them.

    I have attempted leaving the Speed pin pulled high and low but not floating.

    I have modified the PCB schematic to include the zener diode and resistor instead of inductor. I'm expecting those components to come in late next week.

    Thank you!


  • Hello Again,

    The DRV10975Z chip supply current was 39 mA. That seems high based on the expected 11mA typical value in the spec sheet.

    I have set register 0x23 to 0x00 to disable ISD and the break.

    Hopefully I will be able to add the Zener diode in early next week.



  • Joseph,

    You shouldn't be able to communicate when you are in sleep mode. Since the IC is drawing current in mA, I think the IC is not in sleep mode. 39 mA is high. Do you have any other load such as LED etc, connected to the same power supply? Please add the Zener diode and see if this helps.



  • Hi Vishnu,

    Adding the resistor and zener diode fixed the high supply current and the motor now drives properly! Thank you!