Claims
- 1. A power up detection circuit for a device formed on a semiconductor substrate, comprising:
- a CMOS inverter formed of a P-channel transistor, an N-channel transistor, an input and an output, the P-channel transistor biased by a voltage that is coupled to the input; and
- a first and a second N-channel transistor, the first N-channel transistor connected between the N-channel transistor of the CMOS inverter and ground, the second N-channel transistor connected between the first N-channel transistor and a source of the voltage, and the gate of the second N-channel transistor connected to the output of the CMOS inverter for initially applying to the N-channel transistor of the CMOS inverter during power up a potential for keeping the N-channel transistor turned off, thereby preventing the output of the CMOS inverter from being discharge through the N-channel transistor.
- 2. The power up detection circuit of claim 1 further including:
- a third N-channel transistor connected between the input of the CMOS inverter and ground, having a gate connected to the source of the voltage.
- 3. The power up detection circuit of claim 2, further comprising:
- a second P-channel transistor connected between the input of the CMOS inverter and ground, having a gate connected to a substrate.
- 4. A voltage detection circuit, comprising:
- a source for supplying voltage;
- an input node for receiving a voltage from the source;
- an output node for transmitting a signal indicative of whether the received voltage is above or below a value;
- a first N-channel transistor and a second N-channel transistor connected in series between ground and the output node, having their gates connected together to the input mode;
- a third N-channel transistor connected between the series connection of the first and second N-channel transistors and the source supplying the received voltage, and having a gate connected to the output node; and
- a P-channel transistor connected between the output node and the source supplying the received voltage, and having a gate connected to the input node.
- 5. The voltage detection circuit of claim 4 further comprising:
- a second P-channel transistor connected between the input node and ground, having a gate connected to a substrate of semiconductor material that is biased when the received voltage is applied to the input node.
- 6. The voltage detection circuit of claim 5 further comprising:
- a capacitor to couple the source supplying the received voltage to the output node.
- 7. The voltage detection circuit of claim 6 wherein the capacitor comprises:
- a third P-channel transistor having a source and a drain connected together to the source supplying the received voltage and having a gate connected to the output node.
- 8. A power up detection circuit, comprising:
- a CMOS inverter formed on a semiconductor substrate, said substrate biased at a substrate bias potential, said CMOS inverter having an input and an output, and said CMOS inverter being biased between a voltage source reference to ground, the voltage source being different from the substrate bias potential; and
- a P-channel transistor connected between the input of the CMOS inverter and the ground, the transistor having a gate connected to the substrate bias potential.
- 9. The power up detection circuit of claim 8, said inverter comprising:
- a first N-channel transistor connected between the input and the output of the CMOS inverter;
- a first P-channel transistor connected between the input and output of the CMOS inverter, and connected between the first N-channel transistor and the voltage source;
- a second N-channel transistor connected to the output of the CMOS inverter, and connected between the first N-channel transistor and the voltage source.
- a second P-channel transistor connected between the input and output of the CMOS inverter, and connected to the voltage source;
- a third N-channel transistor connected to the input of the CMOS inverter, and connected between the first N-channel transistor and the ground; and
- said inverter presenting a hysteresis effect at the CMOS inverter input as the input switches between voltage levels of the voltage source and the ground.
Parent Case Info
This application is a continuation of application Ser. No. 07/892,388, filed May 27, 1992, which is a continuation of Ser. No. 07/560,934, filed on Jul. 31, 1990, both abandoned.
US Referenced Citations (17)
Continuations (2)
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Number |
Date |
Country |
Parent |
892388 |
May 1992 |
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Parent |
560934 |
Jul 1990 |
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