Four-terminals shunt resistors

[jackjr]

Hi,

I'm working on a 3-phase brushless motor controller project, and I need to sense the current and voltage passing through the MOSFETs.
I'm using the TI DRV8301 IC, a MOSFET gate driver, which also includes 2 current shunt amplifiers for current measurements.

The reference design in the datasheet uses 2 separate shunt resistors. (See attachment for the schematic).

While looking for an ideal resistor, I came across these four-terminals shunt resistors.

So the question is, can I substitute the 2 resistors by only one of these?

[Rerouter]

i would think not, as those 10 milli ohm resistors look to be acting as ballast resistors to even out the current between the mosfets

[baljemmett]

So the question is, can I substitute the 2 resistors by only one of these?

No -- the four-terminal shunt resistors you've found are still only individual resistors, so you'd still need two of them.  The extra pair of terminals are your sense connection -- you pass the current through the 'outer' pair of terminals, and read the voltage drop across the 'inner' pair.  That way you measure the real voltage drop across the resistor, instead of the combined voltage drop across the resistor and the current-carrying connections to it; the technique is called four-wire (or Kelvin) measurement.

(ETA: as, in fact, mentioned in the datasheet you linked!)

[robrenz]

No.  You can use that resistor but you still need two of them.  The 4 terminal resistor will be more accurate at 10m ohms because it eliminates all voltage drop variations that would be in the connection of a 2 lead resistor. Your circuit board has to have the proper layout for the 4 terminal resistor and you have to orient the resistor properly or it may give inaccurate readings if reversed.  There are also board layout techniques for shunts with only 2 leads to give maximum accuracy. It is in this excellent paper http://www.analog.com/static/imported-files/rarely_asked_questions/moreInfo_raq_resistors.html

EDIT:  baljemmett, Sorry I ignored the post warning.

[jackjr]

Too bad 

Thanks for the link Robrenz.
All this seems to be way more complex than I thought…