KR0143036B1 - Sense circuit - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sense circuit, by using an erase cell and a program cell as reference cells, to improve sensing efficiency, and to improve cycle endurance and sensing noise characteristics. It is about a circuit.

Description

Sense circuit

1 is a conventional sense circuit diagram

2 is a timing diagram for explaining FIG.

3 is a typical cycle endurance characteristic diagram of a conventional flash memory cell.

4 is a sense circuit diagram of the present invention.

* Explanation of symbols for main parts of the drawings

1: differential amplifiers 2 to 4: first to third differential amplifiers

The present invention relates to a sense circuit, and more particularly, to a sense circuit using an erase cell and a program cell as a reference cell.

In general, the basic principle of sensing a cell in a flash memory device is to determine a reference cell and to determine the cell current and the reference cell of the cell to be sensed. The principle is to compare the current and read the information contained in the cell by driving the differential amplifier by the cell current difference.

1 illustrates a conventional sense circuit book operation as follows.

The change over time of the sense node (Vt) can be calculated using the following three basic equations.

Where K is a time constant Is defined as At this time, the input differential voltage driving the differential amplifier (1) Is

Finally, the sensing speed (ie, dirvign fordce) is proportional to the difference between Icell and Io. In addition, EEPROM or Flash Memory devices store desired information by electrically programming or erasing a cell. The relative magnitude relationship between the current Ipr and the erased cell current Ier with respect to Io is as follows.

Ier Io Ipr

FIG. 2 is a timing diagram illustrating FIG. 1 with reference to a change in driving voltage ΔV (t) with time t. Based on the above described, looking at the problem of the conventional sensing method,

UV-erased cells are used as reference cells to make Io = (ler + Ipr) / 2, and the driving current (Δi) at this time is

Since Δi = Icell-Io = (Ier-Ipr) / 2, only 50% of the difference between the erase cell and the program cell is used.

In addition, EPI and flash memory cells, unlike other conventional volatile memory cells, program and erase electrons into a floating gate in order to maintain nonvolatile information. Because information is stored by an operation (this operation, which is eared and reprogrammed, is called a cycle), there is an inevitable disadvantage that the characteristics of the cell are degraded as the number of cycles increases. This typical cycle endurance characteristic is shown in FIG. Therefore, due to the cycle endurance characteristic, the weakened earlier of the erase cells and the program cells affects the entire chive speed.

Accordingly, an object of the present invention is to provide a sense circuit that can solve the above disadvantages by using an erase cell and a program cell as reference cells of counterpart cells.

The present invention for achieving the above object is a first and second differential amplifier for first sensing the data stored in the flash memory cell using the erase cell (erase cell) and the program cell (program cell) as a reference cell, And a third differential amplifier configured to perform secondary sensing using the output signals of the first and second differential amplifiers as inputs.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

4 is a sense circuit diagram according to the present invention.

The sense circuit is constructed using three differential amplifiers, and the reference cells in the first and second amplifiers 2 and 3 are erase cells and program cells, respectively. The first sensing is performed, and the second amplification is performed again by the third amplifier 4 to realize very high speed sensing.

That is, by primary sensing

Then again by secondary sensing

If Icell = Ier:

If Icell = Ipr: In this case, the sensing is always performed by the maximum driving current.

As described above, according to the present invention, by using an erase cell and a program cell as reference cells, the sensing efficiency is improved, the cycle endurance characteristic, and the sensing noise characteristic are improved. Has an excellent effect.

Claims (1)

A first differential amplifier for first sensing data stored in the flash memory cell using an erase cell as a reference cell, and a second for first sensing data stored in the flash memory cell using the program cell as a reference cell And a third differential amplifier configured to perform secondary sensing using the differential amplifier and the output signals of the first and second differential amplifiers as inputs.