L6470 - Sensorless Stall Detection

[Flanbix]

Hi,

I wonder if anyone have an experience with the Stall detection of the L6470. I can't find a way to make it detect properly when I stall the shaft by hand.
Adjusting the stall threshold is tricky, the flag is either tripping while running with no load (Set too low) or not tripping at all (Set too high). There is no sweet spot.
Does this feature only work when you are dealing with high current (lets say < 2A), so the change of current is actually meaningful. Or am i missing something...

Thanks.

[zerorisers]

Code: [Select]

Depending on motor speed and load angle characteristics, the L6470 offers a motor stall
condition detection using a programmable current comparator.
When a stall event occurs, the respective fl
ag (STEP_LOSS_A or ST
EP_LOSS_B) is forced
low until a GetStaus command or a system reset occurs (see
Section 9.2.20 on page 66
).

condition detection using a programmable current comparator.

^^ Is it an internal or external comparator?
This is the section of the datasheet I am looking at, it may help. Ill keep searching for more meaningful information

http://www.st.com/web/en/resource/technical/document/datasheet/CD00255075.pdf

EDIT: Also can you include a circut diagram? That could also be beneficial.

[Flanbix]

On page 8 of the datasheet you can see a "Current DACs & Comparators" block link to the "Current sensing" block, so internal one. I guess the threshold set in the register must be setting the DAC which set the threshold on the current comparator.

I am using the evaluation board from ST, EVAL6470H.

[zerorisers]

Motor supply voltage compensation can be en
abled setting high the EN_VSCOMP bit of the
CONFIG register (see Table 22 on page 49, Section 9.1.21 on page 49). If the EN_VSCOMP bit is low, the compensation is disabled and the internal analog-to-digital converter is at the user’s disposal; sampling rate is always equal to PWM frequency

Here is a quote with a diagram that appears to represent usage of the ADC for use of motor supply voltage compensation. Hope this is useful in some way shape or form.

[srg0016]

I have encountered with the same problem. I have found that L6470 rises FLAG (sets STEP_LOSS_A or STEP_LOSS_B bits of STATUS register to 0) much more often during normal operation with free shaft when motor is just accelerating or decelerating. To tell the truth, I haven't seen that L6470 rises FLAG with corresponding STATUS bits when I stall shaft by hand, what seems very strange. I have tried wide range of operating currents and current thresholds.

Did anyone have success on this problem?