Overcurrent protection function of L6470h

[KFan]

Hi,

I designed a board with ​L6470h and tested it. I am confused with the Overcurrent protection function.

It is shown that the capability of L6470h is 7.0 A peak current (3.0 A r.m.s.), but the MAX overcurrent threshold can be set to 6A in register OCD_TH.

I think this threshold is the peak value, but can not find any description for OCD_TH. Please help and make sure whether the threshold in OCD_TH is peak value or RMS. And what is the relationship between the OCD_TH value and the actual driving current?

Thanks.

Kun

[Kurtnelle]

The value is for peak current. This feature is useful if you have a short in the motor (or wires) and you don't want to burn something. If you know the current that the motors can handle at a specific voltage is x and you set the driver to monitor for that current, then when it is exceeded the driver will go HiZ. The current rating has to do with the rating of the mosfets. So, if you are trying to run a motor with a 0.5 Ohm phase resistance on a 12V supply, then even on the lowest power setting it will trigger the over current. I tried this, and I thought (at first) that the vendor sold me bad motors. I ended up having to use 10 Ohm power resistors to get the phase resistance up enough so that the chip would drive the motors (which they did).