DRV8872-Q1: DRV8872DDARQ1 - No Motor Drive with 1uF Capacitor Across Outputs

Samuel Stevenson

Part Number: DRV8872-Q1

Hi,

I am using DRV8872DDARQ1 for motor actuation, we found that one of the motors we are using for the project includes a 1uF capacitor across the outputs.

In this case, the device attempts to drive the motor though does not reach optimal voltage or current to drive the motor.

There is no nFault report.

Once the capacitor is removed the driver works as expected - the motor actuates.

I am just looking for more information on this, there is no output capacitance limit in the datasheet.

Thanks,

Samuel

9 months ago

0 Samuel Stevenson 9 months ago

Prodigy 30 points

Some further information it seems that we achieve an oscillating waveform - our current limit for I-TRIP is 1.6A (0.22Ohm).

It appears that this issue is similar to - https://e2e.ti.com/support/motor-drivers-group/motor-drivers/f/motor-drivers-forum/596540/drv8872-issue-with-a-motor-integrates-capacitor-and-varistor

Though there is no resolution present.

0 Samuel Stevenson 9 months ago

Prodigy 30 points

Increased current limit to 3.6A and see the nFault go low.

0 Shinya Morita 9 months ago in reply to Samuel Stevenson

TI__Mastermind 34905 points

Thank you for your questions. Based on your feedback, 1uF makes impact to your operation.

>>>>Once the capacitor is removed the driver works as expected - the motor actuates.

I am not sure how much current is "expected without 1uF" and how much current is "not expected with 1uF". However if you try slower PFM frequency (e.g 1KHz PWM with 50-80% duty cycle), you may see more motor current than before with 1uF condition.

regards

Shinya Morita

0 Samuel Stevenson 9 months ago in reply to Shinya Morita

Prodigy 30 points

Hi,

Thanks for the quick response, this was my first thought. Though we are seeing some significant effort to realise PWM function in our current application SLU cycle.

Do you think an EVM module be an option for proving this out? Can we drive PWM easily through those?

Kind regards,

Samuel

0 Shinya Morita 9 months ago in reply to Samuel Stevenson

TI__Mastermind 34905 points

Hi Samuel,

EVM's PWM is fixed ~25KHz. Here is comment on EVM user guide.

regards

Shinya Morita

0 Samuel Stevenson 8 months ago in reply to Shinya Morita

Prodigy 30 points

Hi Shinya,

We eventually got some software to drive our device with the 1kHz frequency @50% - 100% with no result.

Still working to try and close this out.

KR,

Samuel

0 Shinya Morita 8 months ago in reply to Samuel Stevenson

TI__Mastermind 34905 points

Hi Sam,

Thank you for the update.

regards

Shinya Morita

+1 Samuel Stevenson 8 months ago in reply to Shinya Morita

Prodigy 30 points

Hi Shinya,

So by operating at 1.25kHz @ 99% duty cycle, also increasing the current limit to max (3.6A) we are able to drive the motor with the capacitor.

Thanks for your help on this.

KR,
Samuel

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DRV8872-Q1: DRV8872DDARQ1 - No Motor Drive with 1uF Capacitor Across Outputs