Flash memory device having single page buffer structure and related programming operations
A flash memory device is provided, and the flash memory device comprises memory cells, a sense node connected to a selected bit line, a load circuit connected to the sense node, and first and second sense and register circuits, each connected to the sense node. The first sense and register circuit is configured to store a first data value in accordance with the voltage level of the sense node during an initial read interval of a multi-bit program operation. The load circuit is configured to selectively pre-charge the sense node in accordance with the data value stored in the first sense and register circuit during a verify read interval of the multi-bit program operation. A multi-bit programming method for the flash memory device is also provided.
1. A flash memory device comprising:
a plurality of memory cells arranged along a plurality of word lines and a plurality of bit lines;
a sense node connected to a selected bit line;
a load circuit connected to the sense node and adapted to selectively pre-charge the sense node in response to a first data value during a read verify interval; and,
a first sense and register circuit connected to the sense node and adapted to store the first data value in accordance with a first voltage level of the sense node,
wherein the first voltage level of the sense node corresponds to a second data value stored in a selected memory cell.
2. The flash memory device of claim 1 , wherein the load circuit comprises:
first and second PMOS transistors connected in series between a power supply voltage and the sense node;
a first NMOS transistor connected between a gate of the first PMOS transistor and a ground voltage; and,
a transistor pair, comprising a second NMOS transistor and a third PMOS transistor, that is connected between the first sense and register circuit and the gate of the first PMOS transistor, wherein the transistor pair is controlled in accordance with a first control signal, the first NMOS transistor is controlled in accordance with an inverted version of the first control signal, and the second PMOS transistor is controlled in accordance with a pre-charge control signal.
3. The flash memory device of claim 1 , wherein the first sense and register circuit is configured to store program data provided through a page buffer decoder circuit.
4. The flash memory device of claim 1 , further comprising:
a second sense and register circuit connected to the sense node and configured to store a third data value in accordance with a second voltage level of the sense node, wherein the second voltage level of the sense node corresponds to a fourth data value stored in a selected memory cell; and,
a switch circuit configured to transfer data from the first sense and register circuit to the second sense and register circuit.
5. The flash memory device of claim 1 , further comprising:
a data output circuit configured to output data from the second sense and register circuit to a data line bus through a page buffer decoder circuit.
6. A flash memory device comprising:
a plurality of memory cells arranged along a plurality of word lines and a plurality of bit lines;
a bit line select and bias block configured to select a group of bit lines comprising at least one bit line of the plurality of bit lines; and,
a page buffer block comprising a plurality of page buffers, each of which corresponds to at least one bit line of the plurality of bit lines, wherein each of the page buffers comprises:
a sense node connected to a selected bit line through the bit line select and bias block;
a load circuit connected to the sense node and adapted to selectively pre-charge the sense node in response to a first data value during a read verify interval:
a first sense and register circuit connected to the sense node and configured to store first data value in accordance with a first voltage level of the sense node, wherein the first voltage level of the sense node corresponds to a second data value stored in a selected memory cell; and,
a second sense and register circuit connected to the sense node and configured to store a third data value in accordance with a second voltage level of the sense node, wherein the second voltage level of the sense node corresponds to a fourth data value stored in a selected memory cell.
7. The flash memory device of claim 6 , wherein the load circuit comprises:
first and second PMOS transistors connected in series between a power supply voltage and the sense node, wherein the second PMOS transistor is controlled in accordance with a pre-charge control signal;
a transistor pair, comprising a first NMOS transistor and a third PMOS transistor, controlled in accordance with a first control signal, and configured to provide a first signal to a gate of the first PMOS transistor in accordance with a fifth data value stored in the first sense and register circuit; and,
a second NMOS transistor controlled in accordance with an inverted version of the first control signal and connected between the gate of the first PMOS transistor and a ground voltage.
8. The flash memory device of claim 7 , further comprising: a switch circuit configured to transfer data from the first sense and register circuit to the second sense and register circuit.
9. The flash memory device of claim 7 , wherein the first sense and register circuit is configured to store program data provided by a page buffer decoder circuit.
10. The flash memory device of claim 7 , further comprising: a data output circuit configured to output data from the second sense and register circuit to a data line bus through a page buffer decoder circuit.
11. The flash memory device of claim 1 , wherein the load circuit selectively pre-charges the sense node in response to the first data value during a “00” verify read interval.