Kelvin Source Terminal on MOSFETs
You could search for &quot;Kelvin source pin&quot; on the manufacturer's web site.
Basically it's a Kelvin connection to the source itself, that bypasses any package parasitics that would screw up your control circuitry's measurement of the source voltage.
Google &quot;Kelvin connection&quot;, and maybe &quot;four wire resistance measurement&quot;.