DRV8307: Motor drive issues

Stephen Vick

Part Number: DRV8307

Would someone mind reviewing the attached RevB schematic and gerbers for this updated Motor Driver Board?

My issue with this revision: I need to drive the motor at 5000 RPM, but the driver board seems to be maxing out at around 2400 RPM. I suspect it's hitting current limit, but not sure. The motor is rated at 6000 RPM at 9 amps. I have a .028 ohm current sense resistor.

5078.motor schematic.pdf Motor Driver Layout_all.pdf

Steve

over 7 years ago

0 Stephen Vick over 7 years ago

Intellectual 380 points

Motor Driver Debug Signals_03--02-17.pdfSupporting scope shots:

0 Rick Duncan over 7 years ago in reply to Stephen Vick

TI__Guru** 114905 points

Hi Steve,

We will investigate and reply soon. Would you also provide the motor specification?

0 Stephen Vick over 7 years ago in reply to Rick Duncan

Intellectual 380 points

Motor specs attached...

LW Motor Specs_RP34M-79.pdf

0 Phil Beard over 7 years ago in reply to Stephen Vick

TI__Expert 4650 points

Hi Stephen,

For your speed specification, are you running your new PCB at 24V? This may be part of the reason your speed is limited in this application. Also, are you able to measure the voltage across your sense resistor? If the voltage is exceeding our VLIMITER specification, the DRV8307 will begin limiting the PWM duty cycle to limit the current.

The minimum specification for VLIMITER is .225 V, so with your sense resistor value of .028 Ohms, this would limit current to approximately 8.03 Amps. For the typical VLIMITER specification of .25, your current limit would be set to 8.92 Amps.

My suggestion would be to first measure the voltage across the sense resistor and determine if the current limit is being engaged. You may also want to consider increasing the VM voltage if your application will allow it.

0 Stephen Vick over 7 years ago in reply to Phil Beard

Intellectual 380 points

Phil,

I don't understand why I would be limited. The motor is rated at 6840 RPM at 24V. I need to get to 5000 RPM. I should be getting better than 8A of current before current sense kicks in, right? My power supply is showing closer to 1.3A at max motor RPM.

Did you review the scope plots I attached showing the Isense waveforms?

Steve

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DRV8307: Motor drive issues