MCT8316ZTEVM: The motor does not turn on its own

Hi Linus,

Could you provide a capture of the nFAULT pin when the nFAULT LED is flashing? Knowing the timing of the flashing can help to determine the fault being reported.

Regards,

Joshua

Hi Joshua,

I have attached a picture of the nFault output. I have also checked whether it is always the same state (of the 6 states) in which the Motor does not start, but this is not the case. If I rotate the shaft mechanically, the motor will start in some positions. So far I have not been able to determine a pattern. As soon as the Motor has started the Speed is adjustable without any problems.

Best,

Linus

Hi Linus,

Just to check, what is the time scale used in the capture you provided, is it 100 ms/div? Also how long does the nFAULT pin stay high before going low again?

Based on what I see, I believe that  a MTR_LOCK fault is occurring but I need a bit more information to be sure.

Could you provide two captures:

1. the phase current, the nFAULT pin, and the input PWM

2. the hall sensor signals (as close to the device as possible), input PWM, and the nFAULT pin

Regards,

Joshua

Hi Joshua,

I only have an oscilloscope with four inputs. That's why I couldn't capture your second picture. The picture one shows the Hall sensors (green = HPA; red = HPB; blue = HPC) and the phase current of OUTC in yellow. The motor runs perfectly here.

The second image shows the phase current (blue), the input PWM (yellow), and the nFAULT pin (red) in the event of a fault.

The second capture zoomed in:

Thanks for your help.

Best,

Linus

Hi Linus,

Can you provide the voltage on the ILIMIT pin? Please measure this voltage as close to the pin as possible.

Regards,

Joshua

Hi Joshua,

I captured a picture of the ILIMIT pin but i'm not sure what resolution you wanted the picture in. I have captured it in two resolutions for now.

Best,

Linus

Hi Linus,

I need some time to look into this. I will get back with you by Friday.

Regards,

Joshua

Hi Joshua,

do you have any news for me as to what the problem might be?

Kind Regards

Linus

Hi Linus,

Was the motor unloaded during the tests or did it have a load? Based on the current information I believe either the motor may require more current at startup than is available. Could you try placing a 10k resistor on R10 or make the resistors on R10 and R11 match so that ILIMIT is set to AVDD/2? Setting ILIMIT to AVDD/2 will set will disable the current limit and give a better chance for the motor to successfully startup.

If changing ILIMIT to AVDD/2 does not solve the issue can you provide capture of the phase current and hall sensor inputs when the motor attempts to startup?

Also, just to check, have you made any changes to the  MCT8316ZTEVM from its default configuration?

Regards,

Joshua

Hello Joshua,

the motor was not loaded during the test. The current fluctuates between 0 and 2 A. I believe that the current of 2 A should be more than sufficient to start the motor. Are the boards tested before delivery so that a defect is excluded? The hardware of the board is in the standard configuration. 

Kind Regards

Linus

Hi Linus,

We do test our EVMs for functionality and all devices are tested to meet datasheet specifications before delivery. I will need to reach out to our team about this issue. I will aim to get back with you by 4/19.

Regards,

Joshua