Input circuit of a semiconductor device
AssigneeMitsubishi Denki Kabushiki Denki
InventorsTadato Yamagata, Hiroshi Miyamoto, Michihiro Yamada
Life of this patent
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Abstract
An input circuit of a semiconductor device includes a P type well formed on the main surface of a semiconductor substrate, and an N type region formed on the main surface in the P type well. A P-N junction is formed by the N type region and the P type well. An input voltage is applied to the N type region, which input voltage is applied to an internal circuit formed on the semiconductor substrate. When the P-N junction is rendered conductive by an application of an excessive voltage to the input voltage, the current caused by the excessive voltage is absorbed to the supply potential through the P type region formed in the P well.
Claims9
An input circuit of a semiconductor device, comprising:
- a semiconductor substrate of a first conductivity type having a main surface and connected to a first potential;
- a first region of said same first conductivity type as said substrate, said first region formed on the main surface of said semiconductor substrate;
- a first region of a second conductivity type different from said first conductivity type formed on said main surface in the first region of said first conductivity type, wherein
- a P-N junction is formed by said first region of the second conductivity type and said first region of the first conductivity type,
- an input voltage applied to said first region of said second conductivity type,
- said input voltage applied to an internal circuit formed on said semiconductor substrate;
- and
- current absorbing means connected to a second region of the first conductivity type formed on said main surface in said first region of the first conductivity type for absorbing, when said P-N junction is rendered conductive by an application of an excessive voltage to said input voltage, current generated by said excessive voltage to a second potential different from said first potential.
An input circuit of a semiconductor device, comprising:
- a semiconductor substrate having a main surface;
- a first region of a first conductivity type formed on the main surface of said semiconductor substrate;
- a first region of a second conductivity type different from said first conductivity type formed on said main surface in the first region of said first conductivity type, wherein
- a P-N junction is formed by said first region of the second conductivity type and said first region of the first conductivity type,
- an input voltage applied to said first region of said second conductivity type,
- said input voltage applied to an internal circuit formed on said semiconductor substrate;
- and
- current absorbing means connected to a second region of the first conductivity type formed on said main surface in said first region of the first conductivity type for absorbing, when said P-N junction is rendered conductive by an application of an excessive voltage to said input voltage, current generated by excessive voltage, wherein
- said current absorbing means comprises a field effect element of said second conductivity type.
An apparatus for controlling a substrate current in a semiconductor device for preventing undesirable current flow to said substrate caused by conduction of a P-N junction, wherein:
- said substrate includes:
- a well,
- an impurity region in said well,
- said substrate and said well having a common conductivity type, and
- a parasitic P-N junction between said well and said impurity region in said well;
- said substrate maintained at a first prescribed potential, comprising:
- P-N junction conduction detecting means for detecting conduction of said parasitic P-N junction;
- and
- excessive current absorbing means for absorbing, when said conduction detecting means detects conduction, excessive current generated by conduction to a second prescribed potential different from said first prescribed potential.
An apparatus for controlling a substrate current in a semiconductor device having a P-N junction parasitically formed on a substrate, for preventing unpreferable current flow to said substrate caused by conduction of said P-N junction, said substrate maintained at a prescribed potential, comprising:
- P-N junction conduction detecting means for detecting conduction of said P-N junction;
- excessive current absorbing means for absorbing, when said conduction detecting means detects conduction, excessive current generated by conduction to a prescribed potential;
- said semiconductor device including a first region of a first conductivity type formed on a main surface of said substrate and including said P-N junction, and
- a second region of the first conductivity type not constituting said P-N junction formed on the main surface of said semiconductor substrate between said excessive current absorbing means and said first region, wherein
- said P-N junction conduction detecting means detects conduction of said P-N junction by detecting a potential of the second region of said first conductivity type.
In a semiconductor device having a parasitically formed P-N junction on a substrate, wherein said substrate includes:
- a well,
- an impurity region in said well,
- said substrate and said well having a common conductivity type, and
- said parasitically formed P-N junction being between said well and said impurity region in said well, a method of controlling substrate current for preventing undesirable current flow to said substrate caused by conduction of the parasitically formed P-N junction,
- comprising the steps of:
- maintaining said substrate at a first prescribed potential,
- detecting conduction of said parasitically formed P-N junction;
- and
- upon detection of said conduction, absorbing excessive current generated thereby to a second prescribed potential different from said first prescribed potential.
Dependencies are inferred from the claim text.