Non-volatile memory circuit
View Patent ↗A non-volatile memory circuit is formed of a P-channel MOS transistor and includes a P-channel non-volatile memory element having a floating gate and a control gate capacitively coupled together. A resistor divider has a first resistor and a second resistor for dividing a voltage difference between a power supply voltage and a ground voltage. A divided voltage output of the resistor divider is connected to the control gate. First and second switches are connected in parallel to the respective first and second resistors. The first and second switches are controlled so that a voltage of the control gate is set to a voltage of the divided voltage output which maximizes an electric field between a pinch-off point and a drain point of the P-channel MOS transistor in a writing mode.
1. A non-volatile memory circuit formed of a P-channel MOS transistor, comprising:
a P-channel non-volatile memory element comprising a floating gate and a control gate capacitively coupled to the floating gate;
a resistor divider comprising a first resistor and a second resistor for dividing a voltage difference between a power supply voltage and a ground voltage, a divided voltage output of the resistor divider being connected to the control gate of the P-channel non-volatile memory element;
a first switch connected in parallel to the first resistor; and
a second switch connected in parallel to the second resistor,
wherein the first switch and the second switch are controlled so that a voltage of the control gate is set to a voltage of the divided voltage output which maximizes an electric field between a pinch-off point and a drain point of the P-channel MOS transistor in a writing mode, and so that the voltage of the control gate is set to the power supply voltage in a reading mode and in a retention mode.
2. A non-volatile memory circuit according to claim 1 , wherein a resistance value of the first resistor and a resistance value of the second resistor are selected so that the voltage applied to the control gate in the writing mode is set in a vicinity of a threshold of the non-volatile memory element in an ultraviolet-erased state.
3. A non-volatile memory circuit formed of a P-channel MOS transistor, comprising:
a P-channel non-volatile memory element having a floating gate and a control gate capacitively coupled to the floating gate; and
resistors connected in parallel to respective switch transistors for adjusting a potential of the control gate so that a potential of the floating gate of the P-channel non-volatile memory element is set in a vicinity of a threshold of the P-channel non-volatile memory element to maximize an electric field between a pinch-off point and a drain of the P-channel non-volatile memory element in a writing mode, the resistors being connected to the control gate.
4. A non-volatile memory circuit according to claim 3 , wherein the control gate of the P-channel non-volatile memory element is connected to a divided voltage output of the resistors.
5. A non-volatile memory circuit according to claim 4 , wherein the resistors comprises a first resistor and a second resistor for dividing a voltage difference between a power supply voltage and a ground voltage; and wherein the switch transistors comprises a first switch transistor connected in parallel to the first resistor and a second switch transistor connected in parallel to the second resistor.
6. A non-volatile memory circuit according to claim 5 , wherein a resistance value of the first resistor and a resistance value of the second resistor are selected so that a voltage applied to the control gate in the writing mode is set in a vicinity of a threshold of the non-volatile memory element in an ultraviolet-erased state.
7. A non-volatile memory circuit according to claim 4 , wherein the control gate of the P-channel non-volatile memory element is connected to the switch transistors.
8. A P-channel EPROM circuit comprising:
a P-channel non-volatile memory element having a floating gate and a control gate capacitively coupled to the floating gate;
a resistor divider having a divided voltage output connected to the control gate; and
switch transistors connected to the resistor divider for controlling a potential of the control gate and a potential of the floating gate so that the potential of the floating gate is adjusted to a vicinity of a threshold of the P-channel non-volatile memory element in an ultraviolet-erased state to maximize an electric field between a pinch-off point and a drain of the P-channel non-volatile memory element in a writing mode.
9. A P-channel EPROM circuit according to claim 8 , wherein the resistor divider comprises a first resistor and a second resistor; and wherein the switch transistors comprises a first switch transistor connected in parallel to the first resistor and a second switch transistor connected in parallel to the second resistor.