Method and apparatus for analog reading values stored in floating gate structures
First Claim
1. A method of reading an analog value stored in a storage cell having a source, a drain, a gate and a floating gate comprising the steps of:
- (a) coupling a first reference voltage to the drain of the storage cell;
(b) coupling a second reference voltage to the gate of the storage cell;
(c) providing an initial load current through the drain and source of the storage cell;
(d) reducing the load current through the drain and source of the storage cell to a value at least one order of magnitude less than the initial load current; and
,(e) providing a read output voltage responsive to the voltage on the source of the storage cell with the reduced load current there through.
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Abstract
This invention utilizes the small cell size of the NAND storage cell structure in an analog storage and playback device. This is achieved, in part, by using a special, zero current storage cell, in which in the read mode, the cell loading current is waveshaped to attain an optimal dynamic range and to avoid the resistive effects of series parasitic resistances of other transistors in the source node or drain node, and to avoid the transistor conductance variations of all the transistors in the read path. The loading current is waveshaped to reduce possible overshoot and settling effects to achieve the fine output voltage resolution in an optimal sensing time. Details of the method and alternate embodiments are disclosed.
107 Citations
18 Claims
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1. A method of reading an analog value stored in a storage cell having a source, a drain, a gate and a floating gate comprising the steps of:
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(a) coupling a first reference voltage to the drain of the storage cell; (b) coupling a second reference voltage to the gate of the storage cell; (c) providing an initial load current through the drain and source of the storage cell; (d) reducing the load current through the drain and source of the storage cell to a value at least one order of magnitude less than the initial load current; and
,(e) providing a read output voltage responsive to the voltage on the source of the storage cell with the reduced load current there through. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. Apparatus for reading an analog value stored in a storage cell having a source, a drain, a gate and a floating gate comprising:
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means providing a first reference voltage to the drain of the storage cell; means providing a second reference voltage to the gate of the storage cell; means providing an initial load current through the drain and source of the storage cell, and then reducing the load current through the drain and source of the storage cell to a value at least one order of magnitude less than the initial load current; and
,circuitry providing a read output voltage responsive to the voltage on the source of the storage cell with the reduced load current there through. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. A method of reading an analog value stored in a storage cell having a source, a drain, a gate and a floating gate comprising the steps of:
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(a) coupling a first reference voltage to the drain of the storage cell; (b) coupling a second reference voltage to the gate of the storage cell; (c) providing an initial load current through the drain and source of the storage cell; (d) reducing the load current of the storage cell through the drain and source of the storage cell; and (e) providing a read output voltage responsive to the voltage on the source of the storage cell with the reduced load current there through. - View Dependent Claims (16)
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17. Apparatus for reading an analog value stored in a storage cell having a source, a drain, a gate and a floating gate comprising:
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means providing a first reference voltage to the drain of the storage cell; means providing a second reference voltage to the gate of the storage cell; means providing an initial load current through the drain and source of the storage cell, and then reducing the load current through the drain and source of the storage cell; and circuitry providing a read output voltage responsive to the voltage on the source of the storage cell with the reduced load current there through. - View Dependent Claims (18)
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Specification