DRV8711EVM: Stepper holding with vibration

Part Number: DRV8711EVM

Our customer has a question about DRV8711EVM.
I'm posting the question for the customer:

++++++++++++++++++++++++++++++++++++++++++++++
We have found the following phenomenon on the DRV8711EVM.

After driving a motor, the motor would vibrate a little while holding.
The wave form of the motor current is observed the current vibrated with unspecified cycle.
It seems the ON time becomes short by adding a switch-noise on the SENSE signal .
(Refer to:Fig1,Fig2)

The phenomenon doesn't always occur, but slight vibration occurs by a high rate.

Question;
Would you let us know the way which stops vibrating ?

++++++++++++++++++++++++++++++++++++++++++++++
Configurations:
DRV8711EVM, VM=48V

Mode: Full Step Blank time :75 ,1.5us
ISGAIN:10 Decay time : 5 ,2.5us
TORQUE:114 ,(2.6A) Time OFF : 10 ,5us
TDRIVEN:11 ,2us DECMODE : 011 ,Mixed decay all time
TDRIVEP:11 ,2us
IDRIVEN:00 ,100mA
IDRIVEN:00 ,50mA

MOTOR;
Hybrid stepping motor - High-torque type,
DC RESISTANCE: 0.6Ω±0.09
INDUCTANCE at 1KHz 1Vrms: 2.6mH
MAXIMUM CURRENT: 3A

The followings are the wave forms;

The followings are resister contents on DRV8711(another settings when abnormal):

// CTRL Register
CTRL_REG.Address = 0x00;
CTRL_REG.DTIME = 0x03; //850ns
CTRL_REG.ISGAIN = 0x01; //Gain of 10
CTRL_REG.EXSTALL = 0x00; //Internal Stall Detect
CTRL_REG.MODE = 0x00; //Full Step
CTRL_REG.RSTEP = 0x00; //No Action
CTRL_REG.RDIR = 0x00; //Direction set by DIR Pin
CTRL_REG.ENBL = 0x01; //enable motor
//1000 11 01 0 0000 0 0 1

/// TORQUE Register
TORQUE_REG.Address = 0x01;
TORQUE_REG.SIMPLTH = 0x01; //100uS Back EMF Sample Threshold
TORQUE_REG.TORQUE = 0x71; //with ISGAIN set to 10 this gives about 1.2 AMP Current Chopper
//1000 0 001 01110001

// OFF Register
OFF_REG.Address = 0x02;
OFF_REG.PWMMODE = 0x00; //Internal Indexer
OFF_REG.TOFF = 0x0A; //5uS Fixed off time, It's same even at 10uS
//1000 000 0 00001010

// BLANK Register
BLANK_REG.Address = 0x03;
BLANK_REG.ABT = 0x00; //disable adaptive blanking time
BLANK_REG.TBLANK = 0x4B; //1.5uS current trip blanking time
//1000 000 0 01001011

// DECAY Register.
DECAY_REG.Address = 0x04;
DECAY_REG.DECMOD = 0x03; //mixed decay at all times
DECAY_REG.TDECAY = 0x05; //2.5uS mixed decay transition time,
//1000 0011 00000101

// STALL Register
STALL_REG.Address = 0x05;
STALL_REG.VDIV = 0x02; //Back EMF is divided by 8
STALL_REG.SDCNT = 0x00; //stalln asserted on first step
STALL_REG.SDTHR = 0x3C; //modifed value?
//1000 10 00 00111100

// DRIVE Register
DRIVE_REG.Address = 0x06;
DRIVE_REG.IDRIVEP = 0x00; //High Side 50mA peak (source)
DRIVE_REG.IDRIVEN = 0x00; //Low Side 100mA peak (sink)
DRIVE_REG.TDRIVEP = 0x03; //High Side gate drive 2uS
DRIVE_REG.TDRIVEN = 0x03; //Low Side Gate Drive 2uS
DRIVE_REG.OCPDEG = 0x00; //OCP Deglitch Time 1uS
DRIVE_REG.OCPTH = 0x00; //OCP Threshold 250mV
//1000 00 00 11 11 00 00

Thank you in advance.

Best regards,
Takishin

7 Replies

  • Hi Takishin-san,

    Please try placing a .1uF capacitor in parallel with the sense resistor, and report the results.

    Rick Duncan
    Motor Applications Team

  • In reply to Rick Duncan:

    Hello Rick-san,

    Thank you for your reply.
    I'll ask them for that.

    Best Regards,
    Takishin
  • In reply to takishin:

    Hello Rick-san,

    >Please try placing a .1uF capacitor in parallel with the sense resistor, and report the results.

    Results:

    Our customer has tried placing a capacitor with the sense resistor (phase-A & B).

    It seems the over-current protection cannot work, and power supply(VM) is over-load and stops.


    Best regards,
    Takishin
  • In reply to takishin:

    Hi Takishin-san,

    I would not expect this behavior. Is it possible there was a problem with the capacitor?

    Would you please re-try with a 10nF capacitor across the sense resistors?

    Thank you.

    Rick Duncan
    Motor Applications Team

  • In reply to Rick Duncan:

    Hello Rick-san,

    Thank you for your reply.

    It should work with the capacitors, shouldn't it?

    I'll ask them for it.

    Best regards,
    Takishin
  • In reply to takishin:

    Hello Rick-san,

    There is a correction on the previous report.

    >It seems the over-current protection cannot work, and power supply(VM) is over-load and stops.

    That is a mistake. Our customer has done wrong wiring.

    The right result is working with slightly vibrating with .1uF capacitor.
    It is the same as before.

    >Would you please re-try with a 10nF capacitor across the sense resistors?

    The result is also working with slightly vibrating with 10nF capacitors.
    It is the same as before.

    Have you confirmed the measures with the EVM?
    If no, would you please confirm the phenomenon with DRV8711EVM?


    Best regards,
    Takishin
  • In reply to takishin:

    Hello Rick-san,

    Thank you for your cooperation.

    Could you get something?


    Best regards,
    Takishin