DRV8307EVM: is this shoot throw or is this incorrect controls?

Hi Scott,

You can see that your board is actually spinning the motor much better than the EVM actually. On the EVM, there are many issues:

- Negative voltage spikes on U, V, and W
- Cut off duty cycle outputs on U, V, and W (cycle by cycle current limiting looks to be the root cause)
- Torque ripple on the current output

Looking at the EVM, either shoot-through currents are happening or the ISEN resistor is too small. The EVM's ISEN resistor = 50mohm, which means any current above 0.25V/0.05 = 5-A will exceed the VLIMITER spec and cause a cycle-by-cycle current limit. Cycle-by-cycle causes the UHSG, VHSG, and WHSG outputs to turn off until the next PWM input, causing smaller PWM output duty cycles and a large current ripple. 

What is the peak voltage and current in this application, and what value of ISEN do you all use?

Thanks,
Aaron

I will try to post this but I would like to get this out a fast as I can …..  I changed the current sense resistor and took this screenshot above :

  The current increased and the hz (frequency) was good but only pumped 2.5 gals/minute compared to the EVM that pump 6 gals/minute ……  The current increase must be all shoot-through.

Current waveform looks great but does not produce anything more than the lower current limit.  Did not change the gals/minute.

This issue has not been resolved...

Hi Scott,

I see your attached waveform of current, but it is in volts and I have no idea what level of current is in the waveform since you did not share your ISEN resistor value. This waveform of current looks good and does not look like it is being limited whatsoever or else you would see ripples in the motor current waveform and average lower peak currents. 

If you are not getting enough power from your application, can you ensure that you are measuring the same current performance from the motor with your PCB as you were with the EVM? Are there any differences between PCB and EVM? Can you share schematic? 

On the PCB, can you share a waveform of the Hall sensors to make sure that they have six 60 degree electrical phases? If there is any difference due to Hall sensor misalignment or bad Hall signals on the PCB then you can see worse commutation. Can you also confirm on the U,V, and W phases on the PCB that the waveforms look good?

I would also ensure that the high-side gate voltages go to VM+VCP (in your application ~34V) when they switch on, and that VCP is measured to be 34V with respect to GND. 

Low side gate voltages will go to 10V when switched on, so make sure those voltages are correct. 

Thanks,
Aaron

Thanks Aaron.... did not have time to update information .... but will...  I follow every thing you wrote...  Will get the appropriate screen shots.... And I need to look at all these waveform again anyway..... 

Hi Scott,

No worries, please keep me posted when you have screenshots available to help further debug. 

Thanks,
Aaron