TMC603-EVAL optional transistors

[OlivierD]

Hello,

I received the evaluation board for the TMC 603 a few days ago. I am currently trying to check out how the Rdson current measurement works and it seems that I need to add those optional transistors to make it work. Am I right? And if I am, should I unplug the existing transistors?

Best regards,

Olivier

[TRINAMIC_BD]

Dear Olivier, yes, you could switch to TO220 MOSFETs. In fact, the on-board FETs then would need to be removed. But, you can also do a first try by just switching to RDSon measurement. The TMC603 will see the sum of the voltage drop in the FETs and the sense-resistors, then. You could also try bridging the resistors.

[OlivierD]

Thanks for the fast reply. One more thing, I noticed on the schematic that connecting the ENRS jumper ties the TEST pin to the ground. Does this mean that it is active low? This seems to be the case but the data sheet does not precise that point.

Thanks for the (fast) support,

Olivier

[TRINAMIC_BD]

Dear Olivier, perhaps you still have the TMC603 datasheet rather than TMC603A datasheet. TMC603A has both options. Yes, you need to tie ENRS_TEST pin low, for RDSon based measurement. Then, the bridge center input pin is used for measuring current.

[OlivierD]

Sorry for that one I ended up seeing it in the data sheet, not where I thought it would be! Thanks anyways and sorry for the bother!