L6472 output voltage detected on motor supply

[MRaff.1]

Hello, 

     I have a board based on the stepper driver L6472. I noticed that, when I do not provide input 12V for the motor (the motor 12V but I provide the 3.3V for the logic (VREG, VDD, SW), I find a voltage of about 2.6V on the VSA, VSB pins. 

I tried to exclude all other possible source on the board and I think that this voltage is produced by the L6472. To have a definitive confirm I should cut some PBC track. Before doing this I would ask if it is an expected behaviour (to have 2.6V at motor output).

[Peter BENSCH · Accepted solution]

The L6472 is a motor driver integrated on a single chip in mixed signal technology. Such chips inevitably have parasitic pn junctions which are in the reverse direction during normal operation and are therefore ineffective. In your case, this parasitic diode is located between VDD (anode) and e.g. VSA (cathode) and forms a circuit with your measuring device. Your VDD of 3.3V reduced by approx. 0.7V of the forward voltage drop of the parasitic diode results in 2.6V - exactly what you measured.

Hope that answers your question?

Regards

/Peter

[MRaff.1]

Thank you very much Peter, yes, you replied to the question. 

Best Regards,

mario