Supply voltage sensing circuit
AssigneeKabushiki Kaisha Toshiba
InventorsRyu Ogiwara, Daisaburo Takashima
Life of this patent
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Abstract
A supply voltage sensing circuit comprises an internal power supply circuit, which provides a constant output voltage regardless of the supply voltage. A delay circuit generates a delayed signal by delaying a variation in the output voltage. A divider circuit generates a divided voltage by dividing the supply voltage at a certain division ratio. A p-type MOS transistor has a source given the delayed signal and a gate given the divided voltage and turns on when the supply voltage lowers below a certain value. An output circuit provides an output voltage based on a drain voltage on the p-type MOS transistor.
Claims8
A supply voltage sensing circuit sensing a variation in a supply voltage, comprising:
- an internal power supply circuit providing a first output voltage that is constant regardless of said supply voltage;
- a delay circuit generating a delayed signal by delaying a variation in said first output voltage;
- a first divider circuit generating a first divided voltage by dividing said supply voltage at a certain division ratio;
- a first p-type MOS transistor having a source given said delayed signal and a gate given said first divided voltage and turning on when said supply voltage lowers below a certain value;
- a first output circuit providing a second output voltage based on a drain voltage of said first p-type MOS transistor;
- a second divider circuit generating a second divided voltage by dividing said supply voltage at a certain division ratio;
- a second p-type MOS transistor having a source given said supply voltage and a gate given said second divided voltage and turning on when said supply voltage rises above a certain value;
- and
- a second output circuit providing a third output voltage based on a drain voltage of said second p-type MOS transistor;
- said internal power supply circuit comprising a bandgap reference circuit, with a temperature characteristic that lowers the first output voltage as the temperature elevates.
A supply voltage sensing circuit, sensing a variation in a supply voltage, comprising:
- an internal power supply circuit providing a first output voltage that is constant regardless of said supply voltage;
- a delay circuit generating a delayed signal by delaying a variation in said first output voltage;
- a first divider circuit generating a first divided voltage by dividing said supply voltage at a certain division ratio;
- a first p-type MOS transistor having a source given said delayed signal and a gate given said first divided voltage and turning on when said supply voltage lowers below a certain value;
- a first output circuit providing a second output voltage based on a drain voltage of said first p-type MOS transistor;
- a second divider circuit generating a second divided voltage by dividing said supply voltage at a certain division ratio;
- a second p-type MOS transistor having a source given said supply voltage and a gate given said second divided voltage and turning on when said supply voltage rises above a certain value;
- and
- a second output circuit providing a third output voltage based on a drain voltage of said second p-type MOS transistor;
- said internal power supply circuit includes a stepdown transistor having one end, which is supplied with a first input voltage that varies with delay compared to a variation in said supply voltage.
Dependencies are inferred from the claim text.