Erase verify for non-volatile memory
First Claim
1. A non-volatile memory comprising:
- an array of non-volatile memory cells arranged in a row and column format such that the columns comprise bit lines including a selected bit line having a bit line current; and
a plurality of comparators for generating indication signals in response to a comparison of a voltage that is representative of the bit line current with a plurality of reference voltages each coupled to a comparator, each reference voltage indicating a different limit of an erase level window, each comparator generating an indication of one of under-erasure, erasure, or over-erasure in response to the comparison.
7 Assignments
0 Petitions
Accused Products
Abstract
A memory device verify system determines a state of memory cells in a memory. The memory includes a memory array having a plurality of memory cells coupled to bit lines. A verify circuit is coupled to the bit lines to determine if memory cells have a erase level that is within predetermined upper and lower limits. The verify circuit can include first and second comparators. In one embodiment, the first comparator is used to compare a bit line current with an upper first reference current. The second comparator is used to compare a bit line current with a lower second reference current. The comparator circuit is not limited to reference currents, but can use reference voltages to compare to a bit line voltage. The verify circuit, therefore, eliminates the need for separate bit line leakage testing to identify over-erased memory cells.
19 Citations
16 Claims
-
1. A non-volatile memory comprising:
-
an array of non-volatile memory cells arranged in a row and column format such that the columns comprise bit lines including a selected bit line having a bit line current; and
a plurality of comparators for generating indication signals in response to a comparison of a voltage that is representative of the bit line current with a plurality of reference voltages each coupled to a comparator, each reference voltage indicating a different limit of an erase level window, each comparator generating an indication of one of under-erasure, erasure, or over-erasure in response to the comparison. - View Dependent Claims (2, 3, 4, 5, 6, 7)
-
-
8. A non-volatile memory comprising:
-
an array of flash memory cells arranged in a row and column format such that the columns comprise bit lines including a selected bit line having a bit line current and the rows comprise word lines; and
a plurality of comparators for generating indication signals in response to a comparison of a voltage that is representative of the bit line current with a plurality of reference voltages each coupled to a comparator, each reference voltage indicating a different limit of an erase level window, each comparator generating an indication of one of under-erasure, erasure, or over-erasure in response to the comparison. - View Dependent Claims (9, 10, 11, 12)
-
-
13. A memory comprising:
-
an array of memory cells arranged in a row and column format such that the columns comprise bit lines including a selected bit line having a bit line current and the rows comprise word lines; and
a plurality of comparators for generating indication signals in response to a comparison of a voltage that is representative of the bit line current with a plurality of reference voltages each coupled to a comparator, each reference voltage indicating a different limit of an erase level window, each comparator generating an indication of one of under-erasure, erasure, or over-erasure in response to the comparison. - View Dependent Claims (14, 15, 16)
-
Specification