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Stepper Motor Noise DRV8711

Erhan Ergun
Intellectual 270 points
Other Parts Discussed in Thread: DRV8711, DRV8711EVM, CSD17506Q5A

Hello,

I am using drv8711 motor driver in my design. I also have DRV8711EVM.

The only differences between my design and DRV8711EVM is mosfets and limit resistor.

My mosfets are CSD17506Q5A and my limit resistor value is 0.01 Ohm.

The problem is, when i connect my stepper motor to EVM and set values there is no noise everything is ok. But when i connect my stepper motor to my driver card, both while motor is just powered or jogging or running, there is an annoying sound like an "open tap" and like there is lots of ripples in power line.

Then i decided to make same noise in EVM, changed every value randomly but could not get that noise. Even i configure awfull values to EVM it works quiter than my motor driver card (in both low and high current applications).

When i look through scope while motor is stepping and while motor stops i got these outputs. (videos)

Stepper motor= st6018L3008-A (parallel connection)
Pulse= external indexer mode (10KHz-30Khz)

Working Current= 4 Amp RMS

For running situation:
http://youtu.be/HABwYoj9sHI

For stopped situation:



Can you help me?





  • 0
    TI__Guru** 114905 points

    Hi Erhan,

    Can you provide the schematic of your EVM, plus the settings you are using during the videos?

    Is this the motor from the EVM? If not, please provide the specs for the motor also.

    Did you include audio on the videos? I cannot hear anything.

    Thanks.

  • 0 in reply to Rick Duncan
    Intellectual 270 points

    Hello Rick,

    I am working to find the reason for 2 days. I realized that the sound problem occured just after changing the limiting resistor. I needed to decrease the value of limiting resistor in order to get higher current values.

    Is there any specs for selecting limiting resistor next to watt spec? I mean my resistos value is very small (0.01 Ohm).

    Now i am thinking about, small value at limiting resistor may couse this problem because my old resistor's value is 0.150 Ohm and i did not get any problem at all.

    My new limiting resistor:(0.01 Ohm)
    http://docs-europe.electrocomponents.com/webdocs/0ef5/0900766b80ef5596.pdf

    My Stepper Motor:(Connected in parallel mode)
    http://en.nanotec.com/fileadmin/files/Datenblaetter/Schrittmotoren/ST6018/L/ST6018L3008-A_neu.pdf

    My old limiting resistor:(0.150 Ohm)
    http://www.yageo.com/documents/recent/PYu-RL_521_RoHS_L_5.pdf

    My Mosfets:

    CSD17506Q5A



    My design is completely same as drv8711evm.



  • 0 in reply to Erhan Ergun
    TI__Guru** 114905 points

    Hi Erhan,

    Did you change the TORQUE and/or ISGAIN settings to match the new sense resistor? If you did not, the chopping current (see equation 1 on page 11 of the datasheet) is now increased by 15x.

    When the sense resistor is changed, at a minimum the TORQUE setting should be adjusted. The ISGAIN setting may also be changed. 

    There are a few guidelines for selecting the sense resistor. Changing one of TORQUE, ISGAIN, or the sense resistor may result in the need to adjust the other two. 

    Keep the maximum voltage across the sense resistor to less than 0.5V.

    Keep the voltage across the resistor X ISGAIN to less than 2.5V (provides a little headroom from the 2.75V)

    The power through the resistor can be adjusted by changing the ISGAIN.

    We have used 5mOhm sense resistors on the EVM with no problem.

    For the 10mOhm resistor and 4.24A chopping, the suggested settings for TORQUE and GAIN are:

    TORQUE 158 79 39 20
    ISGAIN 40 20 10 5

     I suggest you try the ISGAIN of 40 and 20 first.

     

  • 0 in reply to Rick Duncan
    Intellectual 270 points

    Hello folks,

    I solve my problem by changing Rsense resistor by increasing it's value to 75 miliOhm (0.075 Ohm).

    Probably it is because of characeristics of my PCB design (path resistance etc.).

    Thank you for your help.