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