DRV8428: Motor oscillation

graham brown

Prodigy 50 points

Part Number: DRV8428

Motor oscillates instead of maintaining DIR and driver and motor get hot. DIR scopes constant during step pulsing

I have:

VRef 1.27v (R = 100K)

SLEEP and EN/FAULT tied together

VM = 24v

tried all HI LO HIZ settings for M0 M1

used step sizes 100usec to 1000usec

Lots of heat sinking on 4-layer board

Help would be much appreciated.

over 3 years ago

0 Wang5577 over 3 years ago

TI__Guru 56650 points

Graham,

Do you run the DRV8428 on an EVM or your own board? Can you share your schematic and take measurements on the output current?

0 graham brown over 3 years ago in reply to Wang5577

Prodigy 50 points

Thank you Wang5577.

I am using my own board. VRef is controlled by a digipot over SPI which I am still debugging, so VRef is stuck at 1.26v. That may be the problem with the motors.

M0 and M1 are driven by processor pins, so only HI, LO and Hi-Z are available for step setting.

Graham.,

0 Wang5577 over 3 years ago in reply to graham brown

TI__Guru 56650 points

Graham,

The full scale current is about IFS (A) = VREF (V) / 3 (V/A)= 1.26/3 (A)=0.42A. You can add a DC current to the motor winding to see if it is very hot or not.

If the motor is not hot with a DC current, please find a scope and current probe to check the DRV8428 output current to see if there is any abnormal condition.

0 graham brown over 3 years ago in reply to Wang5577

Prodigy 50 points

Simple explanation - motor winding connections were wrong! If this were not my first time working with steppers, the mistake would not have happened. Sorry to bother you.

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DRV8428: Motor oscillation