This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

MCT8316Z: Motor Driver seemingly not turning on/doing anything?

Part Number: MCT8316Z

Hello all,

I am using the MCT8316ZT (hardware variant) on my PCB to drive a BLDC motor. I am still in the first stages of testing but have hit a bit of a snag. The problem is, I am feeding a PWM signal into the motor driver, along with a direction, but the motor driver seemingly does nothing. The motor does not move at all, and the current draw into the system remains unchanged (0.02 A).

Currently I am combing through the datasheet to make sure my external components are correct and that I am configuring the device correctly. I also plan on confirming that the device is soldered on correctly and everything is correctly connected.

However, this is my first time using a device like this so I would like to inquire if anybody else has had similar problems?

My driver schematic is attached. I have not shown how I connect Slew, Advance, Mode, and ILIM. I have simple resistor networks that bias these pins according to the specifications I am looking for. 

Additionally, the driver model is actually the SPI variant, but I made sure to substitute the hardware variant pins for the SPI pins by looking at the datasheet.

Thank you!


  • Hi Nivant,

    Thanks for your question!

    Today is a TI holiday, but we will aim to provide a response by the end of the week.



  • I do have an update. I probed my ILIM volatge and it indicated around 0.4V, which I know is under the allowed voltage for that pin. As such it makes sense that the motor driver pulls no current. I am using the integrated 3.3V LDO (AVdd) in order to bias the ILIM pin to a voltage of 1.25V (AVdd/2 - 0.4). However, I found that the motor driver's 3.3V LDO was outputting around 1.8V instead of 3.3V I suspect this is because I damaged the internal LDO because I was using 5V hall inputs. I found another post where it was suggested that hall inputs higher than AVdd may damage the LDO and as such would damage the device. 

    Maybe you could confirm that my intuition is correct?

  • Hi Nivant,

    I am looking to get you feedback on this question soon. However, I am having a hard time seeing the schematic picture you sent. Can you please provide a higher resolution picture or pdf of the schematic so I can take a closer look?




    There is my schematic. However, currently I am connecting the NSleep pin to 3.3V from a Raspberry Pi (without the pullup shown on the schematic), and I am connecting nFault to an external 3.3V reference. I am doing this because I believe this would be the correct way to wake up the device according to the datasheet. I might be mistaken though.

    Currently, I am trying to measure the output of the internal 3.3V regulator (AVDD) but I am getting 0V. I am getting similar results at the 5V_BK signal shown in the schematic (the internal 5V buck reg.) I believe I am not turning the device on correctly? Maybe you could provide me with a list of things I should check to make sure the device is on? My understanding is that supplying the motor driver a Vm voltage (I am using 29V), pulling Nsleep high via external supply, and pulling NFault high to avoid test mode, should be enough to turn the device on?


  • Hi Nivant,

    While I take a closer look at your schematic and questions, please check out the MCT8316ZTEVM (MCT8316ZT evaluation board) design files and compare your schematic. This is the best way to see TI's default recommendations for using this device in a system to drive a motor. 

    If you have any updates from looking at that, please post them here. If not, no worries, I will try and get back to you on this by the end of the week.

  • One thing worth mentioning is that the board I mentioned above (where I see 0V for AVDD) is a different board from the one I mentioned in my first comment on this thread. As such, I have two boards right now where one board actually has the correct  AVDD and V_BK voltages and the other one does not (I must have done some incorrect probing initially). The problem (on my end) is that the board with the correct voltages is unusable because one of the PCB traces was destroyed. Basically, I have one board that gives me the correct voltages so I am confident that my schematic/layout is at least functionally correct. Even so, I would appreciate someone to look over the schematic...

    I have looked over the design for the MCT8316ZTEVM and haven't seen anything too concerning as it relates to my design.

  • Hi Nivant,

    Please allow me some more time to conduct a proper review of your schematic. I have a feeling that your device may be stuck in sleep mode but it will take me additional time to review your schematic completely. Please review the circuit architecture around your nSLEEP pin to ensure the proper voltages are being applied.



  • Hi Nivant,

    I also do not see any glaring issues with your schematic. However, I am still worried about your LDO output. A general practice that may help is that, as stated in the datasheet, TI recommends components be rated at least twice the normal operating voltage of the device/pin. If you suspect the device may be damaged, could you try replacing the device with another one?

    Can you send me waveforms of nSLEEP and AVDD so I can take a look at them? This may help us determine if the device is escaping sleep mode during startup. Additionally, please review the nSLEEP sections of the datasheet:



  • An update now, I soldered a new board and was able to get both the 3.3V regulator and the buck regulator voltage. They are both operating as expected. This means that the device is correctly out of sleep mode right?

    Unfortunately I am still applying a PWM signal to the driver and getting nothing. That is, the motor does not turn and the current draw into the board is still around 0A. The Ilim voltage is around 1.33V which is a bit high but still within the tolerance (AVDD/2 - AVDD/2 - 0.4). I'm assuming that my Ilim voltage is fine and I should still get the motor to spin? Also nFAULT is remaining low. Charge pump voltage is 33V while Vm is 28V.

  • Hi Nivant,

    Happy to hear that the 3.3V LDO and buck regulator are operating as expected. 

    An ILIM voltage of 1.33V is within the tolerance of your system given your AVDD is 3.3V. Since nFAULT is remaining low, there is a fault condition.

    Can you check if the device is receiving the speed command by monitoring the PWM signal on the PWM pin? If not receiving the speed command, the motor might not spin. 

    Also, please check all of the fault conditions and protections offered by the device that may cause nFAULT to go low by referencing section 8.3.16 of the datasheet.



  • Apologies, I misspoke. nFault is remaining HIGH which means there is no fault signal. I also have a debug LED on the PWM signal and it lights up, so I know the driver is getting a PWM signal.

    Open to more suggestions.

    If nothing else comes to mind (honestly can't think of anything) I might take to a microscope to check all the solder joints and maybe redo some of them. I'm suspecting that the PWM signal is somehow not getting through....

  • Hi Nivant,

    I would try to confirm your suspicions by monitoring the PWM signal on the the PWM pin to see if the device is receiving the speed command, that will hopefully narrow down your debugging. Please do double check all of your solder joints to ensure connectivity throughout your board.



  • An update:

    I am starting to realize that the soldering job on the board is very consequential. I resoldered another motor driver on another board and it started working again (internal regulators output the voltages but PWM still does nothing). I am going to tinker around a bit more here....

    I was wondering what the electrical requirements of the PWM signal are? Is there some kind of PWM amplitude that is needed (3.3V or 5V) or something like that? 


  • Hi Nivant,

    Please refer to the datasheet Electrical Characteristics Table 7.5 where it shows the logic high and logic low voltages for the PWM pin and other pins:

    If I have answered your original question, please submit an new E2E thread with any additional questions so that other customers with similar questions can more easily find the answer. 

    Additionally, if you could help mark this thread as resolved that would be very appreciated.



  • Finally found the issue. I was not using pullups on my hall sensors. The motor turns now but rather inefficiently. I will mark this post as resolved and will scavenge the internet for solutions on how to drive the motor more efficiently. Currently it turns at a constant rpm but is very noisy.