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DRV8711 losting register contents

Albert Haberlander
Prodigy 60 points
Other Parts Discussed in Thread: DRV8711

Hello,

why does the DRV8711 lost its register contents?

e.g. the register 0 was written with the content 0x0D21 and after a while the Motor stopped and the register 0 had the content 0xA42.

The LSB was low, which means that the Motor is disabled.

Over a short time, this happens to all Registers.

What could be the reason for this behavior?

 

  • 0
    TI__Guru** 114905 points
    Hi Albert,

    Are you using a TI EVM or your own board?

    When the registers loose the contents, do they change to the default values? This could be caused by a reset of the device.

    If the registers are changing to a non default value, this could be caused by a SPI command meant for another device. Please check the SCS line for inadvertent writes to the device.
  • 0 in reply to Rick Duncan
    Prodigy 180 points

    Hello,

    I also found that the content of CTRL register has been changed by the DRV8711 chip itself, the original value is below:

    ISGAIN = 0;

    EXTSTALL =0;

    MODE =6;

    after some while , I noticed that the current and microstep has been changed, then I check the content of register as following:

    ISGAIN =3;

    EXSTALL =1;

    MODE =0xF;

    I'm definitely sure that this change is not made by MCU SPI, just step pulse has been issued to DRV8711 in this period. The SIMPTH bit of TORQUE register has also been changed, this phenomena can be frequently observed if I change the DECMOD to 3 (mix decay all time) in high resolution microstep.

    Is it caused by over temperature or other fault?

    Thanks and Regards.

     

  • 0 in reply to liur
    TI__Guru** 114905 points
    Hi Liu,

    We are not aware of register bits changing as you described.

    Faults like overtemp, overcurrent, predriver do not reset the registers. The RESET line does reset the registers to the values listed in the datasheet.

    Are you using the SPI to communicate with other devices? If so, is it possible the SCS input is toggled at the DRV8711 causing inadvertent writes?
  • 0 in reply to Rick Duncan
    Prodigy 180 points
    Hi Rick,

    Thanks for your kindly feedback. I will check the SPI waveform if faults do not change the content of register.

    Liu Rong
  • 0 in reply to Rick Duncan
    Prodigy 180 points

    Hi Rick,

    It may caused by spike on the foot pin of SPI, maximum noise Vpk is about 0.9V, but after we replaced the DRV8711 chip lot, the noise was greatly reduced and the chip work well, the mark on the before lot is "59TG4 C9TD", it is "61TG4 ANNT" on the new lot, so what's the difference between these production lot?

    Thanks!

    Liu