A dotted line in a safe operating area is annotated as “This area is limited by RDS(ON).” What does it mean?

A dotted line in a safe operating area is annotated as “This area is limited by RDS(ON).” What does it mean?

This line represents an area bound by a conduction loss that occurs while the MOSFET is on. Because of its electrical characteristics, the MOSFET cannot operate in an area above the line limited by RDS(ON).

It is represented by the straight line shown in ② in the figure.
This straight line is calculated by the expression ID = VDS / RDS (ON) max.

Maximum Ratings: Power MOSFET Application Notes (PDF:1,075KB)

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