DRV10987: Fault Error VCC_OV and Lock 0(Hardware Current Limit fault)

Hi Sakthi,

Can you enable inductive AVS and try again? Inductive kickback might cause spike on the DC bus and trigger OVP on VCC when stop command is issued. To confirm this, can you monitor the DC bus voltage when you issue stop command?  Do you apply 0% duty on PWM to stop the motor? Device should instantly start driving the motor by entering into ISD after start command is issued.  

Regards,

Vishnu

Hi Vishnu,

Thanks for your message,

Can you enable inductive AVS and try again?

After enable the Inductive AVS VCC_OV error is cleared but we got new fault value(2049) over current error and this happen only when we stopped(0% PWM DC) and restart the motor within a second, If we restart after a sec no fault value is recorded.

Do you apply 0% duty on PWM to stop the motor?
Yes we apply 0% PWM to stop the motor, I just want to get clarified about the stop command, what is stop command? whether 0% DC on PWM or EECTRL(Motor Disable Reg).

Regards,

Sakthi V

Hi Sakthi,

Can you measure the phase current using a current probe and DC bus voltage when you stop and restart within 1 sec? Stop command is when the PWM duty cycle is 0%. 

Regards,

Vishnu

Hi Vishnu,

Above image is the phase current Info




This is the voltage Info,

Both Info is measured at stop command.

Thanks ,

Sakthi V

Hi Sakthi,

I will get back to you on Wednesday!

Regards,

Vishnu

Hi Sakthi,

Apologies for the delay. Is this tested on our EVM or your board? If it is tested on your board, can you share the schematic of your board? I want to check the capacitance across VCC and GND. In the current plot, are you measuring phase/motor current or the DC bus/supply current? If it is phase current then I would expect to see sinusoidal waveform before you issue stop command.

Regards,

Vishnu

Hi Vishnu,

  The waveform attached below as you asked , this is with reference to sakthi Vinayk (my team member). Here when stop the motor and quickly restart within 1 second, the Hardware current fault is occurring, but while the duration between turn off and turn on is greater than 1 second, the hardware current limit fault is not occuring.

Zoomed Phase current and VCC (24V) supply below

This above data is taken from our own board. We have put 10uF ceramic and two 0.1uF capacitors for VCC pins of DRV10987 as per datasheet recommendation. 

Thanks and regards,

R.Sivasuryan

Hi Siva,

Can you tell us the end application that you ar working on? Is it a ceiling fan? Also, do you have motor parameters such as stator resistance and Back EMF constant? If you don't have these values, can you measure them? Instructions are provided in section 8.4.1 in DRV10987 Datasheet. You can also try to decrease the open loop current from 1.6A to 0.8A to see if this helps fix the issue.

Regards,

Vishnu

Hi Vishnu,

  I have sent you the driver schematic and application details to your private message for your reference. 

Regards,

R.Sivasuryan

Hi Vishnu,

We shared the measured back emf value in your personal chat, If we kept the calculated value we get LOCK 0 - Hardware Current limit fault. Kindly check

Regards,

Sakthi V

Hi Sakthi,

I think what is happening here is, when you turn off and ON the power supply within 1 sec, the motor kinetic energy transfers back to the driver supply voltage and we see a voltage overshoot. Can you decrease the driver dead time to 800 ns, set the slew rate to 120 V/us and open loop current to 0.4A or 0.8A? Also, what is the cap value and voltage rating of the caps across VCC and GND?

Regards,

Vishnu

Hi Vishnu,

  Thanks, we will try as per you suggestion and let you know. I have sent you the driver circuit in your private message. In VCC we have put 10uF 50V rated X5R capacitor we have used as suggested in datasheet.

Thanks and regards,

R.Sivasuryan

Thanks, please let us know the feedback. 

Hi Vishnu,

If we modify any values as you mentioned above we get hardware current limit fault while driving the motor and the driver cant able to reach closed loop because of hardware current limit fault

Regards,

Sakthi V

Ok so it looks like the open loop current is higher for your application. Can you replace C71 with a higher cap (20 uF) and try again? This can minimize the overshoot on VCC.