Voltage mode sensing for low power flash memory
First Claim
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1. An electrically erasable flash memory, comprising:
- a plurality of data storage elements configured to store a plurality of data bits, each of said plurality of data bits having a data state;
a reference storage element in addition to said plurality of storage elements configured to store a reference; and
a voltage sensing circuit selectively coupled to individual ones of said plurality data storage elements and said reference storage element and said voltage sensing circuit being configured to bias said individual ones of said plurality of data storage elements and said reference storage element with a bias resistance and to read said data state of said individual ones of said plurality of data bits stored in said plurality of data storage elements;
wherein an output of said reference from said reference storage element provides an indication that data read out from said plurality of storage elements is valid;
wherein each of said plurality of data storage elements has a performance margin;
wherein said voltage sensing circuit is configured to selectively bias said plurality of data storage elements with said bias being at least one of a read bias and a margin bias; and
wherein, when said voltage sensing circuit biases said individual one of said plurality of data storage elements with said margin bias, said individual one of said plurality of data storage elements induces a response indicative of said performance margin of said individual one of said plurality of data storage elements.
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Abstract
Electrically erasable flash memory and method. The memory has a data storage element and a voltage sensing circuit. The data storage element is configured to store data bits, each of the data bits having a data state. The voltage sensing circuit is selectively coupled to individual ones of data bits and is configured to bias the data bits with at least one of a bias current and a bias resistance and to read the data state of the individual ones of the plurality of data bits.
17 Citations
28 Claims
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1. An electrically erasable flash memory, comprising:
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a plurality of data storage elements configured to store a plurality of data bits, each of said plurality of data bits having a data state; a reference storage element in addition to said plurality of storage elements configured to store a reference; and a voltage sensing circuit selectively coupled to individual ones of said plurality data storage elements and said reference storage element and said voltage sensing circuit being configured to bias said individual ones of said plurality of data storage elements and said reference storage element with a bias resistance and to read said data state of said individual ones of said plurality of data bits stored in said plurality of data storage elements; wherein an output of said reference from said reference storage element provides an indication that data read out from said plurality of storage elements is valid; wherein each of said plurality of data storage elements has a performance margin; wherein said voltage sensing circuit is configured to selectively bias said plurality of data storage elements with said bias being at least one of a read bias and a margin bias; and wherein, when said voltage sensing circuit biases said individual one of said plurality of data storage elements with said margin bias, said individual one of said plurality of data storage elements induces a response indicative of said performance margin of said individual one of said plurality of data storage elements. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A memory module, comprising:
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a flash memory cell operatively coupled to a voltage reference and configured to sink a relatively high amount of current in a first state and a relatively low amount of current in a second state different from said first state; a reference memory cell in addition to said flash memory cell configured to store a reference; a bias circuit operatively coupled between a voltage supply and said flash memory cell and said reference memory cell and said bias circuit being configured to form a sensing node between said bias circuit and said flash memory cell and said reference memory cell; and a sensing circuit operatively coupled to said sensing node configured to voltage bias said flash memory cell with a bias and to read said data state of said flash memory cell based, at least in part, on said bias; wherein an output of said reference from said reference memory cell provides an indication when to read said data state of said flash memory cell; wherein said flash memory cell has a performance margin; wherein said sensing circuit is configured to selectively bias said flash memory cell with said bias being at least one of a read bias and a margin bias; and wherein, when said sensing circuit biases said flash memory cell with said margin bias, said flash memory cell induces a response indicative of said performance margin of said flash memory cell. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A method of operating an electrically erasable flash memory having a plurality of data storage elements configured to store a plurality of data bits, each of said plurality of data bits having a data state, a reference storage element in addition to said plurality of data storage elements to store a reference and a voltage sensing circuit, comprising the steps of:
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selectively coupling individual ones of said plurality data storage elements and said reference storage element to said voltage sensing circuit; biasing said individual ones of said plurality of data storage elements with a bias; and
thenreading said data state of said individual ones of said plurality of data storage elements when said reference output from said reference storage element is valid and based, at least in part, on a voltage of said individual ones of said plurality of data bits stored in said plurality of data storage elements; wherein each individual one of said plurality of data storage elements has a performance margin; wherein said bias is one of a read bias voltage and a margin bias voltage; wherein said biasing step, for a normal read, selectively biases said plurality of data storage elements to said read bias to determine said data state of said individual one of said plurality of data storage elements; wherein said biasing step, for a performance margin test, selectively biases said plurality of data storage elements to said margin bias to determine said performance margin of said individual one of said plurality of data storage elements; further comprising the step of determining whether or not said data state read from said plurality of data storage elements for said performance margin test is a correct data state. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28)
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Specification