Circuit with overvoltage protection
AssigneeMotorola, Inc.
InventorJiri Langer
Life of this patent
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Abstract
A circuit (100) has a pull-up transistor (110), a pull-down transistor (120), an input driver (200). The pull transistors (110, 120) pull an output line (102) to first or second reference lines (101, 103). The output line (102) can assume a potential higher than the potential at the first reference line (101). The circuit (100) further comprises protection transistors (150, 160, 170, 180). The protection transistors compare the potential at the output line (102) with the potential at the first reference line (101). The protection transistors keep a substrate line (106) of the pull-up transistor (110) at the potential of the output line (102) or at the potential of the first reference line (101), whichever is higher.
Claims21
A circuit with overvoltage protection, comprising:
- a first node coupled for receiving a first source of operating potential;
- a second node coupled for providing an output potential, OUT;
- a first transistor having first and second main electrodes, a control electrode, and a substrate electrode,
- (a) said first main electrode coupled to said first node,
- (b) said second main electrode coupled to said second node and indirectly coupled for receiving a second source of operating potential, and
- (c) said control electrode coupled to a control terminal for receiving a control signal;
- and
- a second transistor having first and second main electrodes and a control electrode,
- (a) said first main electrode coupled to said substrate electrode of said first transistor,
- (b) said second main electrode coupled to said second node, and
- (c) said control electrode coupled to said first node, said second transistor protecting said first transistor by temporarily pulling said substrate of said first transistor to said second node so that said first transistor is made non-conductive;
- a third transistor having first and second main electrodes, a control electrode, and a substrate electrode,
- (a) said first main electrode coupled to said control electrode of said first transistor,
- (b) said second main electrode coupled to said second node,
- (c) said control electrode coupled to said first node, and
- (d) said substrate electrode coupled to said substrate electrode of said first transistor.
An apparatus comprising:
- a first transistor having
- a substrate with a first doping,
- located on said substrate, a first contact region with a second, opposite doping and coupled for receiving a first potential,
- located on said substrate, a second contact region with said second doping and coupled for providing an output potential, and
- a third contact located between the first contact region and the second contact region and counted for receiving an input signal;
- a substrate driver coupled for receiving said first potential and said output potential and coupling said substrate to either said first contact region or to said second contact region depending on a polarity of a difference between said first potential and said output potential, wherein a portion of said substrate driver is located in said substrate;
- and
- a protection transistor having
- a first contact region located in said substrate, said first contact region with a second, opposite doping and coupled for receiving the input signal,
- a second contact region located in said substrate, said second contact region with said second doping and coupled for receiving the output potential, and
- a third contact located between said first region and said second contact region and coupled for receiving the first potential.
Dependencies are inferred from the claim text.