STSPIN840 minimum voltage for the SNS comperator

[tbe]

Hello, 

I'm currently designing a BDC-motor controller with the STSPIN840 and was wondering how low I can go with the current sensing resistors to minimize the losses across those resistors. Especially at higher currents in parallel mode the resistor losses would become quite large when staying in the region the eval-board is dimensioned. Is there a minimum sense voltage that I should stay above or is it going to be stable no matter how low I push it (assuming the reference voltage is reasonably stable)?

Can I use like 50mOhms there? That would result in a reference voltage of 0.15V when using the 3A limit, so I could probably get away with a single 0.5W sense-resistor.

[Peter BENSCH · Accepted solution]

Welcome @tbe, to the community!

You will find information on this in the data sheet: the voltage at the shunt is compared with the voltages at REFA and REFB. The minimum value of the reference voltage of 100mV can also be found there. This means that you can of course compare with 150mV – if this value is also present at REFA and/or REFB.

Hope that helps?

Regards
/Peter

[tbe]

Thanks for the quick reply, I obviously missed that it's mentioned in the datasheet. I was looking at the electrical characteristics chapter, but now that you mentioned it, I could find the reference voltage in the recommended operation conditions. Thanks :).