Other Parts Discussed in Thread: DRV8711
Our customer has a question about DRV8711EVM.
I'm posting the question for the customer:
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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 ?
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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
