DRV8306: Strange gate voltage and motor cannot start

Hai La

Part Number: DRV8306

Tool/software:

1780.BLDC_DRIVER.pdf

Hi,

I am making a custom BLDC motor driver, here is the schematic. The mosfets I'm using is IRFR3708TRPBF.

The start up sequence is driver -> controller. Controller starting with direction and brake pulled LOW, then PWM setting (1kHz from an ESP32), and lastly is the Enable pin pulled high. The problem is SHx and GHx fluctuating at below 0.5V in a very long sine wave SYNCHRONOUSLY for all 3 phases while GLx remains at 0V. nFault is always high, only turns off when Enable is low, VDS is hooked up to VDD. Hall comparators are received when manually turn the motor, FG outputs signal correctly. The motor does not start or make any sound, total consumption at 24V is around 20mA (Enable HIGH, hall sensors connected).

At this point, after searching around in the forum I cannot find out any problem.

Thank you in advance for any help,
Hai

10 months ago

0 Anthony Lodi 10 months ago

TI__Mastermind 27956 points

Hi Hai,

Thank you for your question! Today is a holiday in the US, but we will have a team member respond this week.

Regards,

Anthony Lodi

0 Hai La 10 months ago in reply to Anthony Lodi

Prodigy 20 points

Thank you for your respond, looking forward for any diagnosis at any time.

0 Manu Balakrishnan 10 months ago in reply to Hai La

TI__Intellectual 1940 points

Hi Hai, Can you share the hall input waveform of all the three inputs HA, HB and HC together?

Regards,

Manu

0 Hai La 10 months ago in reply to Manu Balakrishnan

Prodigy 20 points

Hi,
About the waveform, they are all square wave. I do not have access to more advance equipment so here are some pictures of HA-HB, HA-HC, and HB-HC when manually rotated. I am limited at 2 channel at a time.
HA-HB HA-HB.
HA-HC.

HB-HC.

Not sure if this can help you. Additional information is that the motor is 5065 BLDC.

Thank you,
Hai

0 Manu Balakrishnan 10 months ago in reply to Hai La

TI__Intellectual 1940 points

Let me look at the details and come back on this.

0 Hai La 10 months ago in reply to Manu Balakrishnan

Prodigy 20 points

Hi, is there any update yet?

0 Sachin S 10 months ago in reply to Hai La

TI__Expert 6011 points

Hello Hai,

I will look at this e2e from now on,

Could you please check the following at your end:

1. Please check if the rotor is locked after power up or freely rotating.

2. Also, check if the hall outputs are as expected (you may have to zoom into the time scale and check if they are phase shifted equally)

3. In your first waveform, I see that you have tried to plot the GHx and SHx, could you tell me which signal the other trace corresponds to? (orange trace)

Thanks and regards,

Sachin S

0 Hai La 10 months ago in reply to Sachin S

Prodigy 20 points

Thank you for your reply,

1. It is freely rotated, no resistance.

2. Seems like it slightly out phased from each other.

3. The orange line is PWM signal input. GHx is the same as SHx (the sine wave)

0 Sachin S 10 months ago in reply to Hai La

TI__Expert 6011 points

Hello Hai,

The three hall sensors are supposed to look something like this when the motor is spun.

Could you try all combinations of the hall sensor on the HPA HPB and HPC pins and let me know if any combinations work? Sometimes the hall sensors maybe incorrectly mapped to the pins, hence the motor may never start up.

Regards,

Sachin S

0 Hai La 10 months ago in reply to Sachin S

Prodigy 20 points

it is the same as the figure you provided. Is the order of HPA, HPB, and HPC a factor here?

0 Hai La 10 months ago in reply to Sachin S

Prodigy 20 points

If it is, i will try to swap HPA and HPC with each other.

0 Sachin S 10 months ago in reply to Hai La

TI__Expert 6011 points

Hi Hai,

Yes the order is a factor, so ideally if the hall sensors are matched correctly (A phase of motor -> A phase of driver, Hall sensor A of the motor -> HPA and similarly for B and C phase) the motor will spin up fine. Sometimes, the motor phases and corresponding hall may be mismatched. So you may need to try all 6 combinations to see if any combination works.
Best way to do this is to keep the phase connections constant and rotate through all 6 combinations of the hall sensors to HPx

Regards,

Sachin S

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DRV8306: Strange gate voltage and motor cannot start