Read, Verify Word Line Reference Voltage to Track Source Level

• US 20100157681A1
• Filed: 03/02/2010
• Published: 06/24/2010
• Est. Priority Date: 12/20/2007
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: Sandisk Technologies Incorporated (Western Digital Corporation)
• Inventors: Pan, Feng, Pham, Trung, Woo, Byungki
• Granted Patent: US 8,054,681 B2
• Time in Patent Office: Days
• US Class Current: 365/185.180
• CPC Class Codes: G11C 16/08 Address circuits; Decoders; Word-line control circuits
• CPC Class Codes: G11C 16/30 Power supply circuits

Abstract

A non-volatile memory device has individual pages of memory cells to be sensed in parallel. The memory device includes a source level tracking circuit coupled to receive a predetermined word line voltage from a word line voltage supply and the voltage level at the aggregate source node of one or more pages and coupled to provide to word lines of the memory an output voltage during the sensing operation, where the source level tracking circuit includes an op amp whereby the output voltage is the word line voltage offset by an amount to track the voltage level at the aggregate node and compensate for source bias errors due to a finite resistance in the ground loop.

Claims

1. In a non-volatile memory device having individual pages of memory cells to be sensed in parallel, each memory cell having a source, a drain, a charge storage unit and a control gate for controlling a conduction current along said drain and source, the memory device comprising:

a page source line coupled to the source of each memory cell in a page;

an aggregate node coupled to individual page source lines;

a source voltage control circuit coupled via said aggregate node to a page source line of a selected page for memory operation;

a word line coupling to the control gate of each memory cell of said page;

a word line voltage supply for providing a predetermined word line voltage; and

a source level tracking circuit connectable to receive the word line voltage and the voltage level at the aggregate node and connectable to provide to the word line an output voltage during the sensing operation, including an op amp whereby the output voltage is the word line voltage offset by an amount to track the voltage level at the aggregate node.

2. The non-volatile memory device of claim 1, wherein output voltage is equal to the sum of the word line voltage and a predetermined proportion of the voltage level at the aggregate node on source node.

3. The non-volatile memory device of claim 2, wherein output voltage is equal to the sum of the word line voltage and the voltage level at the aggregate node.

4. The non-volatile memory device of claim 1, wherein the sensing operation is a read operation.

5. The non-volatile memory device of claim 1, wherein the sensing operation is a verify operation.

6. The non-volatile memory device of claim 1, wherein the predetermined word line voltage includes temperature compensation.

7. In a non-volatile memory device having individual pages of memory cells to be sensed in parallel, each memory cell having a source, a drain, a charge storage unit and a control gate for controlling a conduction current along said drain and source, a method of sensing a page of memory cells, comprising:

providing a page source line;

coupling the source of each memory cell of said page to said page line source line;

providing an aggregate node coupled to individual page source lines;

coupling the aggregate node to a source voltage control circuit for a sensing operation;

providing a word line;

coupling the word line to the control gate of each memory cell of said page;

providing a predetermined word line voltage;

receiving the word line voltage and the voltage level at the aggregate node at a source level tracking circuit; and

providing to the word line an output voltage from the source level tracking circuit, the source level tracking circuit including an op amp whereby the output voltage is the word line voltage offset by an amount to track the voltage level at the aggregate node.

8. The method of claim 7, wherein output voltage is equal to the sum of the word line voltage and a predetermined proportion of the voltage level at the aggregate node on source node.

9. The method of claim 8, wherein output voltage is equal to the sum of the word line voltage and the voltage level at the aggregate node.

10. The method of claim 7, wherein the sensing operation is a read operation.

11. The method of claim 7, wherein the sensing operation is a verify operation.

12. The method of claim 7, wherein the predetermined word line voltage includes temperature compensation.