KR20000020229A - Method for trimming reference voltage in memory device - Google Patents

Abstract

PURPOSE: A method for trimming a reference voltage in a memory device is provided to control a reference voltage by performing a programming of a trim cell after testing the reference voltage level. CONSTITUTION: A method for trimming a reference voltage in a memory device relates to a control for an inner voltage level when performing a programming operation or an erasing operation in the memory device. To control the inner voltage, a process for trimming a reference voltage is required. The method for trimming the reference voltage comprises the step of: finding an accurate trim bit by using a test register before programming a trim cell and performing the programming of the trim cell according to the found trim bit.

Description

Trimming Voltage Reference of Memory Device

The present invention relates to a method of trimming a reference voltage of a memory device, and more particularly, trimming after checking an expected margin before trimming a reference voltage to adjust an internal voltage level used when programming or erasing the memory device. A reference voltage trimming method of a memory device.

In the memory device, a reference voltage generator is used to supply a stable and constant voltage to changes in temperature or external power according to recent trends due to high speed, low power, and high integration.

In particular, the regulated voltages of the VPPI, VEEI, VPPD, and VSSAG, which are internal voltages used during the programming or programming of the stack gate flash memory, are adjusted using a reference voltage.

However, since the reference voltage changes with temperature, external power supply variation, and process variation, a fine adjustment circuit is provided in the reference voltage generator to adjust the output value.

The fine tuning circuit is trimmed by cutting the fuse using a fuse and trimming using a nonvolatile memory.

The output value of the trimmed reference voltage can be confirmed by a verification voltage which is verified after programming in the flash memory.

Since the programming verification voltage is set at 6V at high temperature in design, if the programming verification voltage is compared with 6V, if the difference occurs, the trim bit is programmed and trimmed in the trim cell of the fine adjustment circuit.

1 is a block diagram showing a general trim cell.

As shown here, the reference voltage is adjusted according to whether or not each bit of the trim cell is programmed.

In other words, programming 0 to 3 bits raises 0.25V and programming 4 to 5 bits reduces 1V. When the 6 to 7 bits are programmed, the trim cell is configured to increase 1V.

In this way, the adjustment range of each bit is adjusted to compare the programming verification voltage with 6V, and the trim cell is programmed to adjust the reference voltage as much as the difference occurs.

Table 1 is a table that calculates the programming data of the trim cell according to the difference between the programming verification voltage and 6V.

Diff value Programming data Adjustment -2.25 <Diff Fail Fail -2.25≤Diff <-2.0 30H -2 -2.0≤Diff <-1.75 31H -1.75 -1.75≤Diff <-1.5 33H -1.5 -1.5≤Diff <-1.25 37H -1.25 -1.25≤Diff <-1.0 10H -1.0 -1.0≤Diff <-0.75 11H -0.75 -0.75≤Diff <-0.5 13H -0.5 -0.5≤Diff <-0.25 17H -0.25 -0.25≤Diff <0.25 Trim end 0 0.25≤Diff <0.5 01H 0.25 0.5≤Diff <0.75 03H 0.5 0.75≤Diff <1.0 07H 0.75 1.0≤Diff <1.25 40H 1.0 1.25≤Diff <1.5 41H 1.25 1.5≤Diff <1.75 43H 1.5 1.75≤Diff <2.0 47H 1.75 2.0≤Diff <2.25 C0H 2.0 2.25≤Diff <2.5 C1H 2.25 2.5≤Diff <2.75 C3H 2.5 2.75≤Diff <3.0 C7H 2.75 3.0≤Diff <3.25 CFH 3.0 3.25≤Diff Fail Fail

Therefore, when the difference between the programming verification voltage and the reference 6V is in the range of 1.0≤Diff <1.25, the value to be adjusted is 1V, and the value recorded in the trim cell is 40H, and the value '0100 0000' is recorded. Then, only 7 bits are programmed, and as shown in FIG. 1, 7 bits increase 1V, so 1V is adjusted.

However, in order to confirm whether the reference voltage is correctly adjusted according to the trimmed state, it may be confirmed by measuring the reference voltage after the trimming is completed.

However, if the reference voltage value does not exist within the expected margin after the trimming is completed, there is a problem in that reprogramming is required after erasing the trim bit of the trim cell that has already been written.

SUMMARY OF THE INVENTION The present invention was created to solve the above problems, and an object of the present invention is to trim a reference cell using a test register when trimming a reference voltage by comparing a programming verification voltage in a memory device. The present invention provides a method of trimming a reference voltage of a memory device to finally find a value of and to trim.

1 is a view showing the configuration of a general trim cell.

2 is a flowchart sequentially illustrating a method of trimming a reference voltage of a memory device according to the present invention.

In order to achieve the above object, the present invention provides a method of trimming a reference voltage by programming a trim cell by comparing a reference voltage with a programming verification voltage, and using the test register before programming the trim cell. Program a trim cell by finding the correct trim bit.

Each bit of the test register is characterized in that each bit of the trim cell has the same function.

When the trim cell is programmed to adjust the reference voltage, the above method first substitutes the trim cell bit value into the test register and checks the result, and then the trim cell is programmed by programming the trim cell and then outside the adjustment margin range. Anticipate in advance to ensure accurate trimming.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. In addition, this embodiment is not intended to limit the scope of the present invention, but is presented by way of example only.

2 is a flowchart illustrating a method of trimming a reference voltage of a memory device according to the present invention.

The trim cell is erased to adjust the reference voltage (200). After the trim cell is erased, the trim cell is read to determine whether the tram cell has been normally erased (210). The data read from the trim cell is compared with 00H (220). That is, it is checked whether all of them have been erased. Therefore, if the data has not been erased even after repeating by setting the number of repetitions to 5 if all are not erased, the method returns to the step 350 of failing the device (222, 224).

After the trim cell is erased, the programming verification voltage is measured (230). In operation 240, a Diff value is calculated by comparing the measured programming verification voltage with a reference 6V voltage. Based on the calculated value, the adjustment value is determined by referring to the table shown in Table 1 and the programming data to be recorded in the trim cell is determined (250).

In other words, if the Diff value is -1.2V, the adjustment value should be reduced to 1V to -1V value, and the programming data will be '0001 0000' at 10H. That is, 1 bit is lowered because 4 bits are programmed.

Then, the programming data written in the trim cell is recorded in the test register, and the programming verification voltage is measured to determine a value whose reference voltage is changed by the value recorded in the test register (260). A Diff value is calculated by comparing the measured programming verification voltage with a reference voltage of 6V (270).

The calculated Diff value is compared with whether it is in a range of −0.25 ≦ Diff <0.25 (280). If the comparison shows that the Diff value is within this range, the programming data recorded in the test register is programmed into the trim cell (290).

However, if the Diff value exists in the range of 0.25≤Diff <0.5, the adjustment value is set so low that the number of repetitions is set three times and 0.25 is added to the set adjustment value to set the new adjustment value. Returning to step 250 determines the new programming data with reference to Table 1 (285) (286) (287) (288). However, if the Diff is greater than 0.5V and if the repetition is repeated three or more times, the process returns to the step 350 of failing the device (285).

On the other hand, if the Diff value exists in the range of -0.5≤Diff <-0.25, the adjustment value is set too high, and as a way to reduce, set the number of repetitions three times and subtract 0.25 from the set adjustment value to set a new adjustment value Returning to the step 250 of determining the programming data is performed to determine the new programming data with reference to Table 1 (281) (282) (283) (284). However, if the Diff is less than -0.5V and if the repetition is repeated three or more times, the process returns to the step 350 of failing the device (281).

After programming the programming data written in the test register to the trim cell, the trim cell is read (300). The read value is then equal to the value written to the test register (310).

In this case, if not the same, the operation of programming the trim cell is repeated by setting the repetition frequency to 5 times (312) (314). However, if the value of the test register and the value programmed in the trim cell do not match after exceeding five repetitions, the process returns to the step 350 of failing the device.

However, when the values of the trim cell and the test register coincide with each other, the programming verification voltage is measured to check the change of the reference voltage by the trim cell (320). The Diff value is calculated from this measured value to check whether the Diff value is within the range of -0.3 &lt; Diff &lt; 0.3 (330). In this case, if the Diff value does not exist within this range, the process returns to the step 350 of failing the device. If the Diff value exists within this range, the trimming operation is normally terminated (340).

As described above, the present invention provides a trim cell in a test register before programming the trim cell when adjusting the electromotive voltage value by programming a trim cell by measuring a programming verification voltage and verifying a reference voltage level after performing a program in a memory device. By recording the data to be programmed and measuring the programming verification voltage, the result of trimming can be tested in advance to accurately find the programming data to be programmed in the correct trim cell and adjust the reference voltage.

Claims (1)

A reference voltage trimming method of a memory device for trimming a reference voltage by programming a trim cell by comparing a reference voltage with a programming verification voltage, Programming the trimcell by finding the correct trim bit using a test register before programming the trimcell Trimming method of the reference voltage of the memory device, characterized in that.