DRV8301: There is a problem with the C-phase output of the DRV8301

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Part Number: DRV8301

Hello, TI Official:

We have some problems with DRV8301 and need your help.

First of all, let me explain the premise: I found that the motor did not rotate when driving the motor and was accompanied by a current howl, and then I removed the motor and checked the output of DRV8301 and MCU.

1、I used STM32 chip to generate three complementary PWM waves. The figure below only shows phase A and phase B PWM waves, which are correct. The PWM waveform of phase C is also the same as that of phase AB. Shown here is the PWM output of the ABC three-phase high-side MCU (PA8,9,10 of the STM32F1 series), and the ABC three-phase low-test PWM waveform and the high-side are complementary (PB13,14,15).

2、Now the following diagram shows the output signal of DRV8301(GHA-GND,GLA-GND),The situation in phase B is similar to that in phase A(GHB-GND,GLB-GND),From the diagram, they are able to follow the complementary PWM waveform output by the MCU, which is no problem.

3、The first graph below shows the contrasting waveforms of GHA and GHC, GHA in yellow and GHC in green.It is clear that GHA can normally follow the PWM waveform generated by the MCU, while GHC cannot。

The second image shows the waveforms of GHC and GLC,It can be seen that GHC and GLC are neither complementary nor square waves.

So I want to know why the waveforms of GHA, GHB, GLA and GLB of DRV8301 are normal, but the waveforms of GHC and GLC are wrong?

4、In addition, I also tested the waveforms of nFAULT and nOCTW.nFAULT is always a high level,nOCTW is also high when testing phases A and B, which is also normal.

However, when testing for phase C, nOCTW was found to be pulled down.I speculate that the error of the C-phase output waveform of DRV8301 may lead to the simultaneous opening of the upper and lower C-phase

MOS tubes, resulting in an overcurrent alarm.

The figure below shows the waveform of nOCTW.