DRV8308: DRV8308 fault when connect to a controller

By the way, I have changed both the DRV8308 and the isolation chip, but the problem still the same.

A modification not shown in the schematic is that I have added pull up resistors for the spi output of DRV8308, so the problem is not caused by this.

Hello,

Thanks for posting on the MD forum!

Once the system is powered and enabled, if you clear the faults, do they come back?

Regards,

-Adam

Hello Adam,

I try to clear the faults after the system is enabled, but the faults still come back.

What I can't understand is that it seems the faults only come back when connecting the system to an MCU.

Regards.

Hi,

If the MCU is connected and the faults are cleared after device power up and initialization, which faults occur again?

Regards,

-Adam

Hi, 

The CPFAIL, UVLO, and OCP faults occur again, and the value of register 0x2A is 0x0059.

Regards.

Hello,

Please provide a scope image of the VM pin and VCP pin while the device is operating. We need to check if the power supply or charge pump voltages are dipping.

Regards,

-Adam

Hi Adam,

Here is the scope image of the 2 pins, the charge pump voltage seems not dipping but rising when enabled, is this normal?

Regards.

Hi,

The VM and VCP are not dipping so I don't think these are real faults. Likely removing the MCU or similar is causing the issue.

Regards,

-Adam

Hi, Adam

Thank you for your answering to this question, I have found that I connect the U, V, W pins and the HSG pins wrongly, maybe this causing the problem.

I'll make another circuit board and see whether it works.

Regards.

Hello Adam,

I've tried to correct the schematic's mistake and tried to use a DRV8307, but after I made a new board, the problem is still there, that the faults still come out, neither the DRV8308 and the DRV8307.

Sometimes the faults are cleared, which I don't know why, but I can't see any gate control signal from the DRV8308/8307 so the motor won't rotate.

Are there any suggestions?

Regards.

Hi, Adam

I have made a new board and done some tests. To make the test easier, I changed the DRV8308 with the DRV8307 because it has fewer input signals.

The problem is:

When leaving the 3 digital inputs ( Break, Direction, CLKIN ) float, or connecting them to ground, the chip is fine. No faults appear and the FAULTn pin is inactive. But if any of the 3 inputs is set to high, the chip is not working, and the FAULTn pin is active. The fault clear function tried to clear the faults for a period of time, but the faults will come back.

Still don't know why this happens.

Regards

Hello,

Did this get resolved?

I don't see a CLKIN signal, are you asking about the PWM input?

Both BRAKE and DIR have internal pull-down resistors so they will be low if left floating.

Regards,

-Adam