This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DRV8711: DRV8711 doesn't modify torque

Part Number: DRV8711

Good morning

the project I'm working on risks being lost due to the considerable reliability problems encountered on the DRV8711 chip.

I conducted a series of rigorous tests to try and reduce noise.
Although following the guidelines of the texas the results were not excellent.

The very serious thing that I found is that the torque value passed in the register, in fact has no significant effect on the torque of the motor and the current absorbed.
I'll explain :
for the test I set up a test bench consisting of:
Thonichi torque wrench + - 12N / m Fs.
driver board developed internally as per application note
sanyo denky engine 103H7823-1714 4A per phase
Lavolta bench power supply BPS-305
Rigol DS1054 Oscilloscope
Current probe TA

the test showed that:
supply voltage 24Vdc, based on the current IFS 4A, RIsense 0.033ohm, ISGAIN = 10, the TORQUE required is 122.

On the oscilloscope the signal was a distorted triangular sine wave.
With the torque wrench I measured 3.8N / m of Holding torque.
the current displayed on the bench-top power supply 2 A which is not true because it is not considered reliable for the calculation of the true RMS.

Having taken care of the anomalous value of 3.8N / m and of the distortion of the current, I have reduced the value of TORQUE passed to the register ..
After a certain number of attempts I saw that it did not change the distortion, neither the current, nor even the torque holding.
I drastically took the register to TORQUE at 0x0100 and nothing changed.

I ask you why?
if the value that I pass to the torque register is lowered, must the current absorbed be lowered or not?

These are the registers
#define DRV8711_CTRL_UserSetting 0x0121 //
#define DRV8711_TORQUE_UserSetting 0x017A // or 0x0100 does not affect effect on current
#define DRV8711_OFF_UserSetting 0x0030 //
#define DRV8711_BLANK_UserSetting 0x0080 //
#define DRV8711_DECAY_UserSetting 0x0409 //
#define DRV8711_STALL_UserSetting 0x083c //
#define DRV8711_DRIVE_UserSetting 0x0AA5 //
#define DRV8711_STATUS_UserSetting 0x0000 //
Well it does not happen because the DRV8711 has a serious problem inside it !!!
I can be wrong for sure but I would like you to explain to me and those like me who are troubled in the same situation, because this happens ..
I would like to point out that every time I write the Spengo registries and relighting the DRV8711 physically removing and feeding, just to use the most drastic method, but it does not change anything !!
Let's say that I am worried and furious at the choice I made because in texas instruments I have always believed and this time I risk paying at my expense a choice made only on trust in the brand. ...

I expect a quick, decisive answer from you

  • Hi Vito,

    We are sorry to hear that you are experiencing trouble with the DRV8711, and will begin working on this.

    While we are working on this side, can by help by providing some additional information?
    Can you provide scope captures of the currents at 0x017A and 0x0100?
    What step frequency are you operating the motor?
    Does the current look correct at lower step frequencies and then become triangular?
    Can you try running at a 1/8th or 1/4 microstepping and lower the step frequency? Does the current improve?
  • Hi Rick

    OK, this is the condition of the test:

    the step frequency is 24390 Hz

    microstep: 32

    You can see in the attached images that the TORQUE problem does not change:

    ISGAIN10_TORQUE0x7A.jpg

    ISGAIN10_TORQUE0x00.jpg

    ISGAIN10_TORQUE0xFF.jpg

    This is the real problem with this DRV8711 driver.

    The worst accuracy of the noise heat vibrations depends only on this big bug.

    I think in great error in the silicon mask of DRV8711 ..

    Or if you need to give a precise sequence to set the registers that is not declared anywhere in the data sheet.

    Please investigate deeply because our company has been seriously damaged by this problem ..

    I ask other users to verify what I found about it ..

    that is: make the set up of your engine, calculate the TORQUE according to ISGAIN and RIsense, and then with measuring instruments you must verify that changing the value of the TORQUE also varies the absorbed current, the noise, the heat and the distortion of the sine wave. .

    I hope I was wrong in something but from evidence on tests I'm doing the result does not change ..

    By the way: every time I change the TORQUE, I compile the MCU file and restart the hardware by switching it off and on.

    Rick Help me please

  • sorry i found bug in firmware
  • Hi Vito,

    We are very glad to hear you found your issue.

    If it is something that others can benefit from, please share your findings when you have time.