Overdrive period control device and overdrive period determining method

1. An overdrive period control device comprising:

a pre-charge circuit connected to a node on which a potential level is detected and for raising a potential at the node to a first potential;

a delay element one terminal of which is connected to the node;

a charge circuit for supplying a power source voltage to the other terminal of said delay element at an input timing of a signal from an outside and for raising the potential at the node, which has been already raised to the first potential, to the power source voltage;

a comparison circuit for comparing the potential at the node with a reference potential that is larger than the first potential and smaller than the power source voltage and for detecting a timing at which both levels of the potentials coincide; and

a logic circuit outputting a signal indicating a period determined by the input timing of the signal from the outside and the timing in which said comparison circuit detects that both levels of the potentials coincide.

2. The overdrive period control device according to claim 1 , further comprising:

a feedback circuit for supplying a difference between the power source voltage and the reference potential as the first potential to said pre-charge circuit.

3. An overdrive period control device comprising:

a pre-charge circuit for supplying a power source voltage to a node on which a potential level is detected and for raising a potential at the node to the power source voltage;

a delay element one terminal of which is connected to the node;

a discharge circuit for supplying a second potential to the other terminal of said delay element at an input timing of a signal from an outside and for lowering the potential at the node, which has been already raised to the power source voltage, to the second potential;

a comparison circuit for comparing the potential at the node with a reference potential that is larger than the second potential and smaller than the power source voltage and for detecting a timing at which both levels of the potentials coincide; and

a logic circuit for outputting a signal indicating a period determined by the input timing of the signal from the outside and the timing in which said comparison circuit detects that both levels of the potential coincide.

4. An overdrive period control device comprising:

a first pre-charge circuit connected to a first node on which a potential level is detected and for raising a potential at the first node to a first potential;

a first delay element one terminal of which is connected to the first node;

a charge circuit for supplying a power source voltage to the other terminal of said first delay element at an input timing of a signal from an outside and for raising the potential at the first node, which has been already raised to the first potential, to the power source voltage;

a first comparison circuit for comparing the potential at the first node with a first reference potential that is larger than the first potential and smaller than the power source voltage and for detecting a first timing at which both levels of the potentials coincide;

a second pre-charge circuit for supplying the power source voltage to a second node on which a potential level is detected and for raising a potential at the second node to the power source voltage;

a second delay element of which one terminal is connected to the second node;

a discharge circuit for supplying a second potential to the other terminal of said second delay element at the input timing of the signal from the outside and for lowering the potential at the second node, which has been already raised to the power source voltage, to the second potential;

a second comparison circuit comparing the potential at the second node with a second reference potential that is larger than the second potential and smaller than the power source voltage and for detecting a second timing at which both levels of the potentials coincide; and

a logic circuit for outputting a signal indicating a period determined by subtracting a second period, which is determined by the input timing of the signal from the outside and the second timing, from a first period which is determined by the input timing of the signal from the outside and by the first timing.

5. The overdrive period control device according to claim 4 , further comprising:

a feedback circuit for supplying a difference between the power source voltage and the first reference potential as the first potential to said first pre-charge circuit.

6. An overdrive period determining method comprising the steps of:

performing pre-charge to raise a potential at a node on which a potential is detected to a first potential;

after the pre-charge, supplying a power source voltage to the node at an input timing of a signal from an outside via a delay element and raising the potential at the node, which has been already raised to the first potential, to the power source voltage;

comparing the potential at the node with a reference potential that is larger than the first potential and smaller than the power source voltage and detecting a timing at which both levels of the potentials coincide; and

determining an overdrive period in accordance with a period determined by the input timing of the signal from the outside and the timing in which it is detected that both levels of the potentials coincide.

7. An overdrive period determining method comprising the steps of:

performing pre-charge to supply a power source voltage to a node on which a potential is detected and for raising a potential at the node to the power source voltage;

after the pre-charge, supplying a second potential to the node at an input timing of a signal from an outside via a delay element and lowering the potential at the node, which has been already raised to the power source voltage, to the second potential;

comparing the potential at the node with a reference potential that is larger than the second potential and smaller than the power source voltage and detecting a timing at which both levels of the potentials coincide; and

determining an overdrive period in accordance with a period determined by the input timing of the signal from the outside and the timing in which it is detected that both levels of the potentials coincide.

8. An overdrive period determining method comprising the steps of:

performing first pre-charge to raise a potential at a first node on which a potential level is detected, to a first potential;

after the first pre-charge, supplying a power source voltage to the first node at an input timing of a signal from an outside via a first delay element and raising the potential at the first node, which has been already raised to the first potential, to the power source voltage;

comparing the potential at the first node with a first reference potential that is larger than the first potential and smaller than the power source voltage and detecting a first timing at which both levels of the potentials coincide;

performing second per-charge to supply a power source voltage to a second node on which a potential level is detected, and to raise a potential at the second node to the power source voltage;

after the second pre-charge, supplying a second potential to the second node at the input timing of the signal from the outside via a second delay element and lowering the potential at the second node, which has been already raised to the power source voltage, to the second potential;

comparing the potential at the second node with a second reference potential that is larger than the second potential and smaller than the power source voltage and detecting a second timing at which both levels of the potentials coincide; and

determining an overdrive period in accordance with a period obtained by subtracting a second period, which is determined by the input timing of the signal from the outside and the second timing, from a first period which is determined by the input timing of the signal from the outside and by the first timing.