Erase verify for non-volatile memory
First Claim
1. A non-volatile memory comprising:
- an array of non-volatile memory cells arranged in columns using bit lines;
a verify circuit selectively coupled to the bit lines to determine if the memory cells have an erase level that is within an erase level window defined by first and second reference signals; and
a current-to-voltage converter coupled between a selected one of the bit lines and the verify circuit, the current-to-voltage converter comprising;
a resistor; and
an activation circuit having an input coupled to the resistor and an output coupled to the verify circuit.
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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.
34 Citations
20 Claims
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1. A non-volatile memory comprising:
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an array of non-volatile memory cells arranged in columns using bit lines;
a verify circuit selectively coupled to the bit lines to determine if the memory cells have an erase level that is within an erase level window defined by first and second reference signals; and
a current-to-voltage converter coupled between a selected one of the bit lines and the verify circuit, the current-to-voltage converter comprising;
a resistor; and
an activation circuit having an input coupled to the resistor and an output coupled to the verify circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A bit line verify system comprising:
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an array of non-volatile memory cells arranged in columns using bit lines;
a verify circuit selectively coupled to the bit lines and generating an output signal indicative of the memory cells having an erase level defined by a bit line voltage that is within an erase level window defined by first and second reference voltages;
a current-to-voltage converter coupled between a selected one of the bit lines and the verify circuit to generate the bit line voltage in response to a bit line current, the converter comprising;
a resistor;
an activation transistor having a source coupled to the resistor; and
an inverter circuit coupled between a gate of the activation transistor and a drain of the activation transistor, wherein the source of the activation transistor is further coupled to the verify circuit; and
control circuitry to perform erase operations in response to the output signal. - View Dependent Claims (9, 10, 11, 12)
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13. A memory device with an erase verify system, the device comprising:
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a memory array having a plurality of memory cells coupled to a bit line;
a verify circuit for selectively comparing a bit line voltage with a first and second reference voltage and generating a first and a second output signal in response to the respective comparisons;
a first current-to-voltage converter coupled between a selected one of the bit lines and the verify circuit to generate the bit line voltage in response to a bit line current, the first current-to-voltage converter comprising;
a resistor;
an activation transistor having a source coupled to the resistor; and
an inverter circuit coupled between a gate of the activation transistor and a drain of the activation transistor, wherein the source of the activation transistor is further coupled to the verify circuit; and
control circuitry to perform erase operations in response to the first and second output signals. - View Dependent Claims (14, 15)
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16. A memory system comprising:
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a processor for controlling the system; and
a memory device coupled to the processor and comprising;
a memory array having a plurality of memory cells coupled to a bit line;
a verify circuit for selectively comparing a bit line voltage with a first and second reference voltage and generating a first and a second output signal in response to the respective comparisons;
a current-to-voltage converter coupled between a selected one of the bit lines and the verify circuit to generate the bit line voltage in response to a bit line current, the current-to-voltage converter comprising;
a resistor;
an activation transistor having a source coupled to the resistor; and
an inverter circuit coupled between a gate of the activation transistor and a drain of the activation transistor, wherein the source of the activation transistor is further coupled to the verify circuit; and
control circuitry to perform erase operations in response to the first and second output signals. - View Dependent Claims (17, 18, 19)
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20. A memory device with an erase verify system, the device comprising:
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a memory array having a plurality of memory cells coupled to a bit line that has a bit line current indicative of a state of a memory cell;
a first comparator to compare a bit line voltage with a first reference voltage and produce a first output signal;
a second comparator to compare the bit line voltage with a second reference voltage and produce a second output signal;
a current-to-voltage converter coupled between a selected one of the bit lines and the first and second comparators to generate the bit line voltage in response to the bit line current, the current-to-voltage converter comprising;
a resistor;
an activation transistor having a source coupled to the resistor; and
an inverter circuit coupled between a gate of the activation transistor and a drain of the activation transistor, wherein the source of the activation transistor is further coupled to the verify circuit; and
control circuitry to perform erase operations in response to the first and second output signals.
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Specification