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L6472 Spurious Over Current

Question asked by cook.brett on Sep 26, 2014
Latest reply on Oct 3, 2014 by Enrico Poli
I'm having a similar issue as someone else posted last year. We had problems with overheating of the IC, so I increased the slew rate and that helped. But now, we're seeing random over-currents and I am wondering if dropping the fast decay duration alone will be enough. We have several motors in the 3 ohm/ 3mH range, My current parameters are what was recommended for the L6472 Eval board:
POW_SR = 00
ton_min = 4us
toff_min = 21us
toff_fast = 10us
fast_step = 16us
tsw = 48us

The advice given to a previous poster was:


This seems to be an offset effect on the current sensing circuitry.
You can try the following solutions:
- slightly increase the target current, this way the sensing circuitry should work better
- decrease the fast decay duration (the fast decay causes the system to go out of control)
- decrease the slew rate

I tried dropping fast_step to 10us, and it seems to work ok, but the error is intermittent, and I'd like to have some margin. Any suggestions?

Also, I wonder if you can explain why adjusting the SR or fast decay helps.