DRV8833: Output current limited by unexpected value

Hi Jacob,

The issue of this thread is both AISEN and BISEN are short to GND. It is expected that current limit doesn't occur  due to 200mV/0 becoming infinite, which is customer's desire. Why are there still current limit? Or other things to limit current?

Regards,

Hayashi

Ahh my apologies Hayashi-san, I was trying to answer too quickly at the end of the day. Connecting these directly to GND is correct for not using current control at all. 

Hmm do they have an EVM they can compare with? 

Other than that, can you post their schematic and PCB layout?

Best,

Jacob

Hi Jacob, 

They do not have EVM now. But I got received thier schematic.

DRV8833 Circuit.pdf

Regards,

Hayashi

Thanks Hayashi-san, let me look at this tomorrow, apologies busy day today.  Feel free to send them an EVM just in case 

Hi Jacob,

Any updates?

Regards,

Hayashi

Hi,

Thank you for your question. May 27th Monday is national holiday in US. Will feedback to expert back office

Hey Hayashi-san,

Can you clarify what is happening?  Is the device spinning the motor, but the steady state current is only 220mA?  Or is the device unable to start the motor?  Have you monitored the nFAULT pin to see if it is throwing an error?  

Schematic looks great, no issues at all.  A few ideas to try:

• Can you send a pic of the PCB layout?  
• Try increasing the bulk capacitance to see if that helps - 10uF should be plenty for 330mA, but 3.3V doesn't need to dip too much to get below VM < 2.5V into UVLO condition.  Maybe try 47uF just for testing.  
• Could also try increasing VM voltage 
• Is this at 100% duty cycle or PWM?  If PWM, Are you running in Forward-Coast or Forward-Brake mode? 

Best,

Jacob

Hi Jacob,

Let me clarify again. Customer uses each ch to driver one DC motor. The DC motor is spinning when 300mA loaded from DC power supply. However when they uses DRV8833, the motor spins even the motor current is 220mA. And when they increase voltage, it doesn't change motor current.

nFault is always HIGH.

Regards,

Hayashi

Hi Hayashi-san,

It would be helpful if you could get some captures of the output current along with the output waveforms.

Can they send the output and current captures for different VM's as well.

Best,

Keerthi