MEMORY DEVICE WITH POWER NOISE MINIMIZATION DURING SENSING

• US 20090323421A1
• Filed: 06/27/2008
• Published: 12/31/2009
• Est. Priority Date: 06/27/2008
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: SanDisk Corporation (Western Digital Corporation)
• Inventors: Lee, Seungpil, Mui, Man Lung, Nguyen, Hao Thai
• Granted Patent: US 7,751,250 B2
• Time in Patent Office: Days
• US Class Current: 365/185.17
• CPC Class Codes: G11C 16/0483 comprising cells having several storage transistors connected in series
• CPC Class Codes: G11C 16/26 Sensing or reading circuits; Data output circuits
• CPC Class Codes: G11C 5/147 Voltage reference generators, voltage or current regulators; Internally lowered supply levels; Compensation for voltage drops G11C5/141 takes precedence

Abstract

Accuracy of sensing operations, such as read or verify, in a memory device is improved by avoiding fluctuations in a sense amp supply voltage which can occur when different sense amps are strobed at different times. First and second sets of sense amps perform a sensing operation on respective storage elements, such as in an all bit line configuration. The first set of sense amps is strobed at a first time point. In response, a sensed analog level is converted to digital data. The A/D conversion relies on the sense amp supply voltage being accurate. To avoid a fluctuation in the sense amp supply voltage, a bypass path allows the storage elements associated with the first set of sense amps to continue to draw power from the sense amp supply voltage. The second set of sense amps is strobed at a later, second time point.

Claims

1. A sense module in a storage system, comprising:

a first conductive path which couples a power supply to at least one storage element;

a second conductive path which differs at least in part from the first conductive path, and which couples a sense node to the at least one storage element;

an analog-to-digital converter which converts an analog level at the sense node to digital data based on a level of the power supply; and

a third conductive path which differs at least in part from the first and second conductive paths, the third conductive path couples the power supply to the at least one storage element when the analog-to-digital converter converts the analog level at the sense node.

2. The sense module in a storage system of claim 1, further comprising:

switches associated with the first, second and third conductive paths; and

a control circuit which provides control signals to the switches to cause;

(a) the first conductive path to couple the power supply to the at least one storage element during a pre-charge phase of a sensing operation of the at least one storage element, (b) the second conductive path to couple the sense node to the at least one storage element during a sensing phase of the sensing operation which follows the pre-charge phase, (c) the analog-to-digital converter to convert the analog level at the sense node to the digital data based on the level of the power supply during an analog-to-digital conversion phase of the sensing operation which follows the sensing phase, and (d) the third conductive path to couple the power supply to the at least one storage element during the analog-to-digital conversion phase.

3. The sense module in a storage system of claim 2, wherein:

the control circuit provides control signals to the switches to interrupt the first and second conductive paths so that they do not couple the power supply to the at least one storage element during the analog-to-digital conversion phase.

4. The sense module in a storage system of claim 1, wherein:

the at least one storage element is in a NAND string which is coupled to a bit line, and the first conductive path couples the power supply to the at least one storage element via the bit line.

5. The sense module in a storage system of claim 1, wherein:

the at least one storage element is connected in series in a set of storage elements.

6. A set of sense modules in a storage system, comprising:

at least first and second sense modules which receive a common power supply;

the first sense module comprising a first sense node and a first analog-to-digital converter, the first sense module couples the first sense node to at least a first storage element to sense a condition of the at least a first storage element, and the first analog-to-digital converter converts an analog level at the first sense node to first digital data at a first time based on a level of the common power supply;

the second sense module comprising a second sense node and a second analog-to-digital converter, the second sense module couples the second sense node to at least a second storage element to sense a condition of the at least a second storage element, and the second analog-to-digital converter converts an analog level at the second sense node to second digital data at a second time which is after the first time based on the level of the common power supply; and

the first sense module includes a respective conductive path for coupling the common power supply to the first storage element during a time period which includes the second time, while the first sense node is decoupled from the at least a first storage element during the time period.

7. The set of sense modules in a storage system of claim 6, wherein:

the first sense module further comprises a respective charge storing component which is coupled to the first sense node; and

the second sense module further comprises a respective charge storing component which is coupled to the second sense node.

8. The set of sense modules in a storage system of claim 6, wherein:

the at least a first storage element is in a first NAND string which is coupled to a first bit line, and the first conductive path couples the common power supply to the at least a first storage element via the first bit line.

9. The set of sense modules in a storage system of claim 6, wherein:

the at least a first storage element is connected in series in a first set of storage elements; and

the at least a second storage element is connected in series in a second set of storage elements.

10. The set of sense modules in a storage system of claim 6, wherein:

the at least a first storage element comprises a first non-volatile storage element; and

the at least a second storage element comprises a second non-volatile storage element.

11. The set of sense modules in a storage system of claim 6, wherein:

the first sense module senses the condition of the at least a first storage element, and the second sense module senses the condition of the at least a second storage element, both as part of a read or verify operation.

12. The set of sense modules in a storage system of claim 6, wherein:

the time period spans at least the first and second times.

13. The set of sense modules in a storage system of claim 6, wherein:

the second sense module includes a respective conductive path for coupling the common power supply to the second storage element during the time period, while the second sense node is decoupled from the at least a second storage element during the time period.

14. A storage system, comprising:

a plurality of storage elements and associated sense modules, including a first set of storage elements and an associated first set of sense modules, and a second set of storage elements and an associated second set of sense modules;

a control circuit which provides control signals to the associated sense modules; and

a common power supply coupled to the associated sense modules;

the control circuit;

(a) instructs the first set of sense modules to provide, based on a level of the common power supply, and at a first time in a first time period, digital data which is indicative of respective states of the first set of storage elements, and to couple the common power supply to the first set of storage elements during the first time period, and (b) instructs the second set of sense modules to provide, based on the level of the common power supply, and at a second time in the first time period which is after the first time, digital data which is indicative of respective states of the second set of storage elements.

15. The storage system of claim 14, wherein:

each sense module of the associated first set of sense modules comprises an analog-to-digital converter which includes the common power supply as an input and a level of a respective sense node as another input.

16. The storage system of claim 15, wherein:

each respective sense node of the associated first set of sense modules is coupled to a respective storage element in the first set of storage elements at the first time.

17. The storage system of claim 15, wherein:

each sense module of the associated first set of sense modules comprises a respective charge storing component which is coupled to the respective sense node.

18. The storage system of claim 17, wherein:

in a second time period which precedes the first time period, the control circuit instructs the associated first set of sense modules to couple the respective charge storing components to the respective storage elements of the first set of storage elements via the respective sense nodes, and to couple the common power supply to the first set of storage elements.

19. The storage system of claim 14, wherein:

the control circuit instructs the associated second set of sense modules to couple the common power supply to the second set of storage elements during the first time period.

20. The storage system of claim 14, wherein:

each storage element in the first and second sets of storage elements is provided in a respective NAND string.

21. The storage system of claim 14, wherein:

each storage element in the first and second sets of storage elements is provided in a respective series-connected chain of storage elements.