Electrically programmable memory, method of programming and method of reading
First Claim
1. An electrically programmable memory comprising:
- a floating gate FET cell having;
a drain electrode, anda source electrode;
means for applying to one of the drain and source electrodes a first relatively high voltage for a programming time;
means for applying to the other of the drain and source electrodes a second voltage less than the first voltage for the programming time, the second voltage being variable between more than two levels so as to determine the quantity of charge induced on the floating gate FET cell and thereby to determine a multi-level value programmed into the cell substantially independently of the programming time.
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Accused Products
Abstract
An electrically programmable memory comprising: a floating gate FET cell (10) having: a drain electrode, and a source electrode; means for applying to the drain electrode a first voltage (VPP) for a programming time (TP); means for applying to the source electrode a second voltage (VML) for the programming time, the second voltage being variable between more than two levels so as to determine the quantity of charge induced on the floating gate and thereby to determine the multi-level value programmed into the cell substantially independently of the programming time. A multi-level value programmed into the cell is sensed by placing an iteratively or dynamically varying voltage on the source electrode, and current flow in the cell is sensed to determine the voltage on the floating gate.
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Citations
10 Claims
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1. An electrically programmable memory comprising:
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a floating gate FET cell having; a drain electrode, and a source electrode; means for applying to one of the drain and source electrodes a first relatively high voltage for a programming time; means for applying to the other of the drain and source electrodes a second voltage less than the first voltage for the programming time, the second voltage being variable between more than two levels so as to determine the quantity of charge induced on the floating gate FET cell and thereby to determine a multi-level value programmed into the cell substantially independently of the programming time. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method of programming an electrically programmable memory comprising:
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a floating gate FET cell having; a drain electrode, and a source electrode;
the method comprising;applying to one of the drain and source electrodes a first relatively high voltage for a programming time; and applying to the other of the drain and source electrodes a second voltage less than the first voltage for the programming time, the second voltage being variable between more than two levels so as to determine the quantity of charge induced on the floating gate FET cell and thereby to determine a multi-level value programmed into the cell substantially independently of the programming time.
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8. A method of reading an electrically programmed memory comprising:
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a floating gate FET cell having; a drain electrode; and a source electrode, the method comprising; applying to one of the drain and source electrodes a third voltage; and applying to the other of the drain and source electrodes a fourth, varying voltage, less than the third voltage; and sensing current flow in the cell so as to determine a multi-level value programmed into the cell. - View Dependent Claims (9, 10)
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Specification