Power-off detection circuit
AssigneeTexas Instruments Incorporated
InventorHiroshi Watanabe
Life of this patent
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Abstract
The object of the invention is to provide a power-off detection circuit with low power consumption and little dependence on power supply voltage. Detecting capacitor 11 is charged by the power supply voltage Vcc. When the power supply voltage Vcc drops at the time of power off, the drop is detected by starting transistor 14. Said detecting transistor 11 is discharged, and the discharge current is supplied to gate voltage generating circuit 21. Gate voltage generating circuit 21 generates a gate voltage depending on the discharge current. As a result, output transistor 17 is turned on, and the signal at control terminal 35 is inverted. Another circuit can detect the power-off state depending on the signal at control terminal 35.
Claims6
A power-off detection circuit comprising:
- a diode, which is electrically coupled between first and second power supply terminals,
- a first capacitor, which is electrically coupled between the diode and the second power supply terminal and is charged from the first power supply terminal via the diode,
- a first output transistor, which is electrically coupled between the first and second power supply terminals to output logic signals,
- a control transistor, which is electrically coupled between a first node connecting the diode to the first capacitor and the control terminal of the first output transistor, with its control terminal electrically coupled to the first power supply terminal,
- a voltage generating circuit, which is electrically coupled between a second node coupling the control transistor to the control terminal of the first output transistor and the second power supply terminal, wherein the voltage generating circuit comprises a second capacitor coupled in parallel to the first capacitor via the control transistor whereby current discharged from the first capacitor charges the second capacitor to change the state of the output transistor.
Dependencies are inferred from the claim text.