Patent ID: 7279773

Claim:
A protection circuit for MOSFETS driving inductive loads, comprising: a plurality of independently switched MOSFETs each having a source and a drain connected in series with a separate inductive load; a plurality of basic unit Zener diodes connected in series to form a stacked Zener diode external of the MOSFETs, the stacked Zener diode having a cathode and an anode and having a desired breakdown voltage less than the breakdown voltages of the MOSFETs, wherein each of the basic unit Zener diodes is formed in a first-type substrate, and wherein each of the basic unit Zener diodes comprises: a second-type well formed in the substrate; a second-type Zener region formed in the second-type well; and a first-type+ region formed over the second-type Zener region between a first and second second-type+ region, wherein the drain of each of the plurality of MOSFETs is coupled through a separate pass diode to the cathode of the stacked Zener diode and the source of each of the plurality of MOSFETs is coupled to a point of common potential with the anode of the stacked Zener diode, each of the pass diodes having a cathode connected to the cathode of the stacked Zener diode.