EEPROM writing and reading method
AssigneeOki Electric Industry Co., Ltd.
InventorTakuji Yoshida
Life of this patent
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Abstract
An electrically erasable programmable read-only memory receives a single supply voltage and a ground voltage, and generates a first voltage higher than both the supply voltage and the ground voltage, and a second voltage lower than both the supply voltage and the ground voltage. Each memory cell in the memory has a nonvolatile storage transistor with a floating gate. To erase the memory cell, the first voltage is applied on a first side of the floating gate and th second voltage is on a second, opposite side of the floating gate. To program the memory cell, the second voltage is applied on the first side of the floating gate, and the first voltage is applied on the second side of the floating gate.
Claims20
A method of writing and reading data in an EEPROM using a single supply voltage, the EEPROM including a memory cell array having a plurality of memory cells, each memory cell comprising a storage transistor having a source and a drain, a floating gate and a control gate disposed over the floating gate, said method comprising steps of:
- the method of writing data including steps of,
- applying a first voltage higher than both the supply voltage and a ground voltage to at least one of the source and drain of the storage transistor of each of selected memory cells, the first voltage being generated from the single supply voltage;
- and
- applying a second voltage lower than both the supply voltage and the ground voltage to the control gate of the storage transistor of each of the selected memory cells, the second voltage being generated from the single supply voltage,
- whereby electrons are released from the floating gate when both the first and second voltages are applied to the storage transistor by said applying steps for writing data, and
- the method of reading data including steps of,
- applying the first voltage to the control gate of the storage transistor of each of selected memory cells;
- and
- applying a second voltage to at least one of the source and drain of the storage transistor of each of the selected memory cells;
- whereby electrons are injected to the floating gate when both the first and second voltages are applied to the storage transistor by said applying steps for reading data.
Methods of writing and reading data in an EEPROM using a single supply voltage, the EEPROM including a memory cell array having a plurality of memory cells, each memory cell comprising a storage transistor having a source and a drain, a floating gate and a control gate disposed over the floating gate, said method comprising steps of:
- the method of writing data including the steps of,
- applying a first voltage higher than both the supply voltage and a ground voltage to at least one of the source and drain of the storage transistor of each of selected memory cells, the first voltage being generated from the single supply voltage by using a first built-in charge pump circuit;
- and
- applying a second voltage lower than both the supply voltage and the ground voltage to the control gate of the storage transistor of each of the selected memory cells while the first voltage is applied to at least one of the source and drain, the second voltage being generated from the single supply voltage by using a second built-in charge pump circuit,
- whereby electrons are released from the floating gate when both the first and second voltages are applied to the storage transistor by said applying steps for writing data, and
- the method of reading data including steps of,
- applying the first voltage to the control gate of the storage transistor of each of selected memory cells;
- and
- applying a second voltage to at least one of the source and drain of the storage transistor of each of the selected memory cells;
- whereby electrons are injected to the floating gate when both the first and second voltages are applied to the storage transistor by said applying steps for reading data.
Dependencies are inferred from the claim text.