DRV8426: nfault condition?

Additionally, in the circuit , measured VM = 24v VCP = 24v .

Hello Furkan,

The VCP voltage should be equal to 5+VM when nSLEEP is logic HIGH. If you are reading VM=VCP when the device is active, it could mean the device is damaged.

Are you using the DRV8426 evaluation board or your own custom board?

Have you replaced the IC with a new one? Was the problem solved?

Regards,

Pablo Armet

Motor Drives Application Engineer

I've replaced new IC, VCP voltage is 28 V now. (VM+4) But nFAULT voltage is 2.8 V is when the device is active . Is it normal?

Hi,

The datasheet specifies a typical VCP voltage of VM+5V. VM+4V is still acceptable. What VCP and CPL/CPH capacitor values are you using in your design?

ı am using datasheet reference design values

I've never seen any Aout or Bout pulse on oscilloscope . I am toggling step pin 1ms interval .

Hello,

As long as the capacitors values are what are recommended in the datasheet, there should be no problems. I recommend checking the VM voltage to make sure it is a stable 24V.

As for the nSLEEP voltage, is nSLEEP pulled up to DVDD?

nSLEEP is pulled up to 5V voltage regulator.Is this create problems?

and ENABLE pin is pulled up to 5V regulator too

That's okay. However, nFAULT should be 5V when no fault is present. There must be something else pulling nFAULT lower than 5V. Can you share your schematic of the driver? You can share via private message.

Pablo , in first design we didn't tied to DVVD capacitor to GND . We tied it and problem solved. But we've another problem .

When I give 5V to STEP pin 1 ms interval. A phase is pulsing correctly 1ms. But B phase of motor is permanently 24V. It's never pulsing.

Do you have any idea about this problem?

Additionally , Is the VM 100uF cap is necessary ? We didn't tied it.

Hello, Fatih,

It needs some bulk capacitors on the VM to absorb the energy sending back from the motor winding. But, the bulk capacitor may not related to this issue.

DRV8426 provides the output current regulation. The output voltage is just a result to get the current setting. What is the full scale setting; micro-stepping setting and output current?

Regards,

Wang Li

VREF voltage is 3.3V and microstepping index is 1/32.

Hello, Fatih,

What is the bridge B and bridge A output current?

I am trying to understand B phase current when it has 24V; also compare bridge B and A output current with the indexer table value. 

If you can provide a test waveform, it may speed up the debugging process.

Regards,

Wang Li