Patent ID: 7592677

Claim:
A semiconductor device, comprising: a substrate; a power transistor formed on the substrate, wherein the power transistor includes first and second terminals and a control terminal and has a first characteristic breakdown voltage across the first and second terminals, and wherein the power transistor has a first geometric layout such that the first characteristic breakdown voltage is determined by a first layout distance of the power transistor; and a voltage-sensing transistor formed on the substrate, wherein the voltage-sensing transistor is coupled across the first and second terminals, wherein the voltage-sensing transistor has a second characteristic breakdown voltage that is less than the first characteristic breakdown voltage, wherein the voltage-sensing transistor has a second geometric layout such that the second characteristic breakdown voltage is determined by a second layout distance of the voltage-sensing transistor, and wherein the voltage-sensing transistor provides a control signal to the power transistor to turn on the power transistor when the voltage across the first and second terminals reaches the second characteristic breakdown voltage.