| US 7,583,114 B2 | ||
| Supply voltage sensing circuit | ||
| Ryu Ogiwara, Yokohama (Japan); and Daisaburo Takashima, Yokohama (Japan) | ||
| Assigned to Kabushiki Kaisha Toshiba, Tokyo (Japan) | ||
| Filed on Mar. 09, 2007, as Appl. No. 11/684,214. | ||
| Claims priority of application No. 2006-105607 (JP), filed on Apr. 06, 2006. | ||
| Prior Publication US 2007/0236260 A1, Oct. 11, 2007 | ||
| Int. Cl. H03L 7/00 (2006.01) | ||
| U.S. Cl. 327—142 [327/143] | 8 Claims |
| 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.
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