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DRV8711: Predriver fault

Harris Triantafillidis
Prodigy 50 points
Part Number: DRV8711

Hi

I have desing a board to drive a stepper motor (nanotec ST5918) using the DRV8711

The motor should be able to execute some turns (30) with speed 150rpm, then stop for 3 seconds and then continue for 30 more turns, and so on

Vm =24V ,FET= IRLR8743 (Rd=0,031, Qq=39nC), Rsense= 0,047

The motor runs at 150rpm (2000steps,1/4 step) with 1,2A

The DRV8711 registers are set as below:

REGISTERS_0 0xD10

REGISTERS_1 0x138

REGISTERS_2 0x4D 

REGISTERS_3 0x1FF

REGISTERS_4 0x50A

REGISTERS_5 0x900

REGISTERS_6 0xF55

Everything works fine, but after some time (from 30minutes to 3 hours) the motor stops and i have a predriver fault.

I played a lot with increasing and decreasing the values of TDRIVE and IDRIVE but nothing change.

Before i try to place in series resistors (47-100) at low side of FETS, i would like to know if there is something that i sould change (registers) that might help

Thanks in advance

  • 0
    TI__Guru** 114905 points
    Hi Harris,

    Please try changing register 6 from 0xF55 to 0x555 (IDRIVEP=100mA/IDRIVEN=200mA). Lowering the IDRIVE may reduce the noise in the system. You may need to examine the FET gates to determine how well this works for you.

    You could also try a lower setting such as 0x455 (IDRIVEP=IDRIVEN=100mA).
  • 0 in reply to Rick Duncan
    Prodigy 50 points

    Dear Rick

    Thanks for your advice.

    I changed the register 6 (OCPTH=750mV, OCPDEG=8us, TDRIVEN=2us, TDRIVEP=500ns, IDRIVEN=200mA, IDRIVEP=100mA) and the system runs (30hours now) without any errors.

    Because we'll move to production soon, do you thing that it will help if i add the resistors (47-100ohm) in series to the low side of Fets?

    The customers will have the ability to change the speed ( from 120rpm to 180rpm) will it have any affect?

    Thanks in advance

  • 0 in reply to Harris Triantafillidis
    TI__Guru** 114905 points
    Hi Harris,

    We are glad to hear the system is now running without errors.

    If you are concerned the predriver faults could re-appear, you can place a 0 Ohm resistor in series with the low side FETs. If necessary, the resistors and register settings can be changed based on future findings.

    If you do change to the 47 to 120 Ohm series resistor, please note the datasheet recommendation to increase the dead time.