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DRV11873: DRV11873PWPR

Part Number: DRV11873
Other Parts Discussed in Thread: , DRV10987, DRV10975, DRV10975EVM, DRV10987EVM

Dear Sirs,

We use your evaluation board DRV11873EVM to test the DRV11873 PWPR again, still found the same problem.  

The motor start stop frequently at the voltage 7.3Vdc, attached the photo for your reference, please help to solve the problem.

  Click here to play this video

  • Hi Adolf,

    Thanks for posting your question in E2E. Can you share the below info?

    1. Maximum motor speed

    2. Number of pole pairs.

    3. Stator resistance Rph.

    4. BEMF Constant, Kt. 

    DRV11873 has a fixed MAX speed limit of the internal control logic. The limit is FG < 475Hz@FS=0 and 950Hz@FS=1.

    Do you have all the jumpers installed? Does RD pin go high indicating a fault?

    Did you connect the COM of the motor to the COM pin?

    On a side note: This driver is meant for fan motor drive applications, and might not be optimized for your motor. There are very few settings to tune with this driver. An alternative part to suggest is the DRV10975 or DRV10987, which allow for far more customization for more motor types.

    Regards,

    Vishnu

  • Dear Vishnu,

    Thank you for the information and inquiry, we reply as follow.

    1. Maximum motor speed   -  Max speed 13000rpm, we test around 7500rpm, the start stop happened. 

    2. Number of pole pairs.   -   2 pairs.

    3. Stator resistance Rph.   -   1.6 ohm

    4. BEMF Constant, Kt.    -   Ke: 0.9mV/rpm; Kt: 8.6mN. m/A

    DRV11873 has a fixed MAX speed limit of the internal control logic. The limit is FG < 475Hz@FS=0 and 950Hz@FS=1.  -   We did try FS connect to 5V and GND, but the problem still happened.

    Do you have all the jumpers installed? Does RD pin go high indicating a fault?  We have not use, nothing test on such pin.

    Did you connect the COM of the motor to the COM pin?  Yes, we did connect the COM of the motor to the COM pin.

    We use your evaluation board DRV11873EVM to test the DRV11873 PWPR, we may try in your side to test from 7.0 to 7.5V on every 0.1V, you may found the start stop happen.

    About the alternative part to suggest is the DRV10975 or DRV10987, do you have the evaluation board for testing?  If so, please inform and or provide.

    Thanks.  Best regards.

    Adolf Lau

  • Adolf,

    Thanks for sharing the details. Note that FS is latched upon power to the EVM so power must be cycled in order for the FS output to change. I would recommend you to remove the jumper J3 and power cycle because your motor is a high speed, low resistance motor. What is the motor voltage rating? Note that the maximum speed can be achieved only when the supply voltage is greater than or equal to the rated motor voltage. You cannot expect the motor speed to be at maximum speed throughout the Vcc range. With Jumper J4 connected, can you check and see if the RD pin as shown in the below pic is pulled high?

    Regarding the alternative part, yes both devices have evaluation boards. Please check DRV10975EVM and DRV10987EVM. 

    Regards,

    Vishnu

  • Dear Vishnu,

    Thank you for the information, we change the FS state to operate in the power off state, and then switch on the power again.

     We remove the jumper J3 and power cycle, but nothing improved.

    The rated voltage of the motor is 14V, our application is 6-12V, no need to have the maximum speed.  It is not the problem of maximum speed, the problem is  ≤7.2V normal, ≥7.4V is normal, but 7.3V the motor will intermittently stop, then start stop again and again.

    Can you please try to test by using your evaluation board DRV11873EVM, testing voltage in between 7.2V to 7.4V to found the start stop problem and help to solve it.

    Thanks.  Best regards.

    Adolf Lau

  • Dear Vishnu,

    How about the motor, any special requirement of the motor?  

    The motor is 3 phases.

    1. Maximum motor speed   -  Max speed 13000rpm, we test around 7500rpm, the start stop happened. 

    2. Number of pole pairs.   -   2 pairs.

    3. Stator resistance Rph.   -   1.6 ohm

    4. BEMF Constant, Kt.    -   Ke: 0.9mV/rpm; Kt: 8.6mN. m/A

    Thanks.  Best regards.

    Adolf

  • Adolf,

    Did you check the status of RD pin? We need this information to know if the motor has entered a lock protection state.

    Do you see this behavior when Vcc ramps through 7.3V or when the Vcc is set constant at 7.3V? 

    Regards,

    Vishnu 

  • Dear Vishnu,

    Thank you for the information and inquiry, it is OK on 7.3Vdc under your evaluation board, but we need to test any problem on other voltage.

    Also we re-design a new board according to your evaluation board and test again, we shall confirm you when everything OK.

    Thanks.  Best regards.

    Adolf

  • Adolf,

    Thanks for the update. You may close this thread by clicking the "Resolve" button. You can open a new thread if you find any other issues.

    Regards,

    Vishnu

  • Dear Vishnu,

    Thank you for the information, it seems the I.C. running well, nothing stop/start again on 7.3Vdc.

    We would like to know the reason, why?  Why FS=L has start/stop problem, FS=H has no problem?  

    Also the problem is limit on 7.3V - 7.5V, other voltage has no problem?

    You can easy to point out the problem, is it you have lots of customers complaining the same problem?

    Thanks.  Best regards.

    Adolf

  • Hi Adolf,

    When the FS pin is tied to GND, the DRV11873 is set for optimized startup for low fan speed motors with high motor winding resistance and high inductance. With the jumper out, the FS pin pulls up to VCC through a pull-up resistor. When the FS pin is tied to VCC, the DRV11873 is optimized for startup for high speed fan motors with low motor winding resistance and high inductance. I am not sure why there is a problem specifically in that voltage range. Also, we haven't seen such issues in the past. 

    Regards,

    Vishnu

  • Dear Vishnu,

    Thank you for the information, we have nothing problem now.

    Thanks.  Best regards.

    Adolf