Patent ID: 7583114
Filing Date: 2009-09-01
Classification: G01R,G11C

Abstract:
1. 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.