KR100555557B1 - Method for setting a write current for a high temperature condition in hard disk drive - Google Patents

Abstract

The present invention relates to a method of setting a write current of a hard disk drive, and more particularly, to a method of setting a write current (WC) for minimizing Adjacent Track Erasure (ATE) at high temperatures.

According to the present invention, a method for setting a light current suitable for high temperature includes determining a light current (R_WC) suitable for room temperature and an overshoot current (H_OSC) suitable for high temperature based on an optimal bit error rate (BER); Using a random write current (WC) and the overshoot current (H_OSC) suitable for the high temperature, data is written to the tracks adjacent to the target track as many times as the temperature is suitable, and the data recorded in the target track is read to read the bit error rate ( Measuring BER); Checking whether the measured bit error rate (BER) satisfies a bit error rate corresponding to a threshold value of a write current in which a weak write occurs; Repeating the process of measuring and checking the bit error rate (BER) while changing a value of a write current (WC) if the measured bit error rate (BER) does not satisfy a bit error rate corresponding to the threshold value; And when the measured bit error rate BER satisfies the bit error rate corresponding to the threshold, setting the write current WC at this time to the light current H_WC suitable for high temperature.

Description

Method for setting a write current for a high temperature condition in hard disk drive}

1 illustrates a configuration of a hard disk drive 100.

2 is a block diagram showing a detailed configuration of the electronic circuit 120 shown in FIG.

3 is a flowchart illustrating a method of setting a light current suitable for high temperature according to the present invention.

The present invention relates to a method of setting a write current of a hard disk drive, and more particularly, to a method of setting a write current (WC) for minimizing ATE (Adjacent Track Erasure) at high temperature.

A hard disk drive is a recording device used for storing information. Typically information is recorded on concentric tracks on either side of one or more magnetic recording disks. The disk is rotatably mounted on the spin motor, and the information is accessed by read / write means mounted on an actuator arm that is rotated by a voice coil motor. The voice coil motor is excited by the current to rotate the actuator and move the head. The read / write head senses the change of magnetism coming out of the surface of the disk and reads the information recorded on the surface of the disk. To write to the data track, current is supplied to the head. The electric current generates a magnetic field, which magnetizes the disk surface.

By reducing the head / disc distance, the recording density can be increased. This reduces the size of the head and positions the head as close to the disk as possible. However, if the head / disc distance is reduced, adjacent tracks may be overwritten by the magnetic field generated by the head, which may result in erasure of data recorded in the adjacent tracks. This phenomenon is called Adjacent Track Erasure (ATE). ATE is an important issue when the write current provided to the head is too high. On the other hand, the adjacent track at high temperature may also be worse due to the decrease in coercivity of the media.

In order to cope with this, a recent hard disk drive has a write current (WC) or over shoot current (OSC) or a boost through a drive temperature measurement (actually, a preamp stage temperature measurement). Current) is used.

That is, at high temperatures, lower write currents WC and overshoot currents OSC are used to prevent ATE from deteriorating.

Japanese Patent Application Laid-open No. Hei 10-340412 stores the optimum value of the write current set in correspondence with the temperature in the storage means through the recording channel optimization process, detects the operating temperature of the hard disk drive, A method of reading and using an optimum value of a corresponding write current from a storage means is disclosed. At this time, the write current set corresponding to the temperature is set to a value that minimizes a bit error rate (BER) when data is recorded at the corresponding operating temperature. The write current optimization method in the user environment is performed by the controller of the hard disk drive.

Hard disk drives are manufactured through processes such as servolite → functional test → burn-in test. In the servo light process, the positional information is recorded on the disk. In the functional test process, it is determined whether the maintenance cylinder is defective and whether the data area can be read or written. The burn-in test process determines whether the data region is defective. In particular, in the burn-in test process, a read channel optimization process for optimizing a read channel of a hard disk drive and a write channel optimization process for optimizing a write channel are performed.

In the burn-in test process, setting the optimal write current (WC) corresponding to the temperature is preferably performed while changing the operating temperature of the hard disk drive. However, since the burn-in test process is actually performed at room temperature or constant temperature conditions, the temperature condition is replaced by the replacement condition, that is, the number of recordings on the adjacent tracks. In other words, instead of changing the temperature, the write current WC that satisfies the lowest BER is searched while varying the number of recordings for the adjacent tracks in proportion to the difference between the low temperature threshold temperature, that is, the temperature that is the basis of the low temperature determination.

In practice, the threshold temperatures that are the criteria for determining the low temperature, the room temperature, and the high temperature are set, and when it is determined that the high temperature and the low temperature are set, the light current WC and the overshoot current OSC are uniformly set by a predetermined value than those at room temperature. The low or high setting method is mainly used.

However, the conventional write current optimization method emulates the high temperature condition by applying only the alternative condition, that is, the number of writes differently, instead of actually applying the temperature, and only considers the ATE at high temperature, which can degrade the recording quality. It is not considering other factors. Therefore, what is found to be the optimum recording current for temperature is in fact approximated or inaccurate.

As described above, the conventional write current optimization method does not fully consider the phenomena that may occur when the hard disk drive is operated at high temperature, and unexpectedly, the BER may be caused by excessive write current or excessive write current in the user environment. Rather, there is an increasing problem.

The present invention has been devised to solve the above problems, and an object thereof is to provide an improved method for optimizing the write current at high temperature.

Light current setting method suitable for high temperature according to the present invention for achieving the above object

Determining a light current (R_WC) suitable for room temperature and an overshoot current (H_OSC) suitable for high temperature based on an optimal bit error rate (BER);

Using the arbitrary write current (WC) and the overshoot current (H_OSC) suitable for high temperature, write data to the tracks adjacent to the target track the number of times suitable for high temperature conditions, read the data recorded on the target track, and read the bit error rate (BER). Measuring);

Checking whether the measured bit error rate BER satisfies a bit error rate BER_ct corresponding to a threshold value of a write current in which a weak write occurs;

Repeating the process of measuring and checking the bit error rate (BER) while changing the value of the write current (WC) if the measured bit error rate (BER) does not satisfy the bit error rate (BER_ct) corresponding to the threshold value; And

And if the measured bit error rate BER satisfies the bit error rate BER_ct corresponding to the threshold value, setting the write current WC to a write current H_WC suitable for high temperature. .

Here, the bit error rate BER_ct corresponding to the threshold refers to a bit error rate BER corresponding to a write current higher by a predetermined value in consideration of margin than a write current in which weak writes occur. .

In addition, the bit error rate BER_ct corresponding to the threshold value is changed according to the recording capacity of the hard disk drive, and it is preferable that the higher the recording capacity of the hard disk drive, the lower.

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

The present invention is characterized in that the write current H_WC suitable for high temperature conditions is determined not to satisfy the best BER as in the prior art, but to satisfy the minimum recording quality of the hard disk drive.

Specifically, in the conventional art, the number of write currents WC applied to the head is measured by recording a predetermined number of times, for example, 1,000 times in tracks adjacent to the target track, and reading the data recorded in the target track to measure the BER. It carried out by changing, and set the light current WC at the time of showing the best BER to the light current H_WC suitable for high temperature conditions.

However, since these test conditions are emulations of high temperature effects and only ATE considerations, BER at high temperatures is not as expected and even hard disk drives fail as expected in real-world applications. It also happens.

The present invention changes the criterion of satisfying the best BER to a condition that satisfies the minimum recording quality in the hard disk drive, thereby ensuring the lowest recording quality against any effect that may occur at high temperatures, and as a result the hard disk drive Prevents it from being treated as defective.

1 illustrates a configuration of a hard disk drive 100. The hard disk drive 100 includes a disk 102 that is rotated by the spin motor 104. The spin motor 104 is mounted on the base plate 106. Actuator arm assembly 108 is also mounted to base plate 106. Actuator arm assembly 108 includes a plurality of heads 110 each mounted to corresponding flex arms 112. The curved arms 112 are attached to an actuator arm 114 that can rotate around the bearing assembly 116. Assembly 108 also includes a voice coil (not shown) coupled with magnet 118 mounted to base plate 106. Energy is applied to the voice coil to move the heads 110 relative to the disk 102. Typically there is one head for each disk face. The spin motor 104, voice coil and heads 110 are connected with a plurality of electronic circuits 120 mounted on the printed circuit board 122. Electronic circuitry 120 typically includes read channel circuitry, microprocessor-based controllers and random access memory (RAM) devices.

2 is a block diagram showing a detailed configuration of the electronic circuit 120 shown in FIG. Electronic circuit 120 includes preamplifier 172 coupled to read / write (R / W) channel circuit 174. R / W channel circuit 174 includes R / W automatic gain control (AGC), filter circuit 176, full wave rectifier 178 and peak detector 180. Electronic circuit 120 further includes a microprocessor-based servo controller 182, which includes an analog-to-digital converter (ADC) 184, a digital signal processor (DSP) 186, a burst sequencer, Memory 190, such as a timing circuit 188 and a random access memory (RAM) device. DSP 186 includes logic circuit 192.

The electronic circuit 120 is coupled with one of the magnetic heads 110 that senses the magnetic field of the magnetic disk 102. When reading servo information located in the servo field area 10 above the disk 102, the head 110 generates a read signal corresponding to the magnetic field of the disk. The read signal is first amplified by the preamplifier 172 and then sent to the R / W channel circuit 174. AGC data included in the read signal is sent to the R / W AGC and filter circuit 176. In the R / W AGC and filter circuit 176 the R / W AGC circuit 176 monitors the AGC data provided by the read signal and then the read signal is filtered in the filter of the R / W AGC and filter circuit 176. . The full wave rectifier 178 rectifies the read signal and sends the rectified read signal to the peak detector 180. The peak detector 180 detects the amplitude of the read signal. The read signal is then fed to an ADC 184 which provides the binarized samples of the analog read signal. The binarized signal is then provided to a logic circuit 192 located within the DSP 186. The logic circuit 192 generates a position signal Q based on the A, B, C and D servo bits read by the head 110. The resulting position signal Q will then be stored in the memory 190 and later provided to the actuator arm assembly 108 to move the head 110. Alternatively, the position signal Q can be provided directly to the actuator arm assembly 108 to move the head 110.

3 is a flowchart illustrating a method of setting a light current suitable for high temperature according to the present invention.

First, the write channel optimization at room temperature is performed to obtain the light current R_WC suitable for room temperature and the overshoot current H_OSC suitable for high temperature. (S302) Here, the light current R_WC suitable for room temperature and the over suitable for high temperature are obtained. The chute current H_OSC is determined to satisfy the optimal BER.

The coercivity of the media decreases at high temperatures and increases at low temperatures. In addition, the ATE characteristic of the head is deteriorated due to the decrease in the coercive force of the media at high temperatures and the decrease in the flying height of the head due to the protrusion of the head by Thermal Pole Tip Protrusion (TPTP). Here, TPTP refers to a phenomenon in which the pole tip of the recording head expands due to heat generated in the recording head, and as a result, the gap between the head and the disk is narrowed.

Therefore, at high temperatures, a lower overshoot current is used than at room temperature to counteract the coercive force reduction.

An overshoot current H_OSC suitable for high temperature and an arbitrary write current WC are applied to the head (s304). Here, the arbitrary write current WC has a minimum value MINIMUM_WC that can be applied to the head. It is preferable.

Data is recorded a predetermined number of times in tracks adjacent to the target track, and the BER is measured by reading the data recorded in the target track (S306). Here, the predetermined number refers to the number of times for the high temperature test and is greater than the number of times for the room temperature test. For example, if the number of recordings for the ATE test at room temperature is 600 times, the number of recordings for the ATE test at high temperature is about 1,000 times. BER is expressed as a log function of the number of bit errors.

It is checked whether the measured BER is greater than or equal to BER (BER_ct) that satisfies the minimum writing quality of the hard disk drive. (S308) Here, the write current satisfying the minimum writing quality of the hard disk drive is weak write (WEAK WRITE). It has been observed statistically that is set to a value slightly above the threshold of the light current to be expressed.

The reason is that the value of the light current suitable for high temperature is set slightly higher than the threshold at which WRITE WRITE develops, so that the value of light current set for high temperature conditions can be avoided even if it is not actually accurate. Because.

In addition, the value of the write current corresponding to BER (BER_ct) that satisfies the minimum recording quality of the hard disk drive is also set in accordance with the value of the write current suitable for high temperature, that is, slightly higher than the write current in which WEAK WRITE is expressed.

In a hard disk drive, when the write current WC is smaller than an appropriate value, WRITE WRITE occurs, and conversely, when the write current WC is large, an ATE phenomenon occurs.

If the BER is not greater than the BER (BER_ct) value that satisfies the minimum recording quality of the hard disk drive in step S308, it is determined that the state is in the WRITE WRITE state and the value of the write current is increased by ΔWC value (S310).

It is checked whether the value of the write current is smaller than the write current R_WC suitable for room temperature (S312).

If the value of the write current is smaller than the write current (R_WC) suitable for room temperature in step S312 to return to step S306.

If the value of the write current is not smaller than the appropriate write current R_WC at S312, the process proceeds to S314. This is because, in S312, if the value of the light current is not smaller than the light current (R_WC) suitable for room temperature, there is no meaning to determine the light current suitable for high temperature. In other words, at a high temperature, the write current is smaller than the write current at room temperature in response to the decrease in the coercive force.If the write current of the hard disk drive is not satisfied, but not smaller than the suitable light current (R_WC) at room temperature, This is because there is no sense in determining the appropriate light current.

If the BER measured in S308 is equal to or greater than BER (BER_ct) that satisfies the minimum recording quality of the hard disk drive, the write current at this time is taken as the write current H_WC suitable for high temperature.

In the embodiment of the present invention, the difference value DIFF_WC between the light current R_WC suitable for room temperature and the light current H_WC suitable for high temperature is calculated (S314).

When the hard disk drive is used in a high temperature condition, the difference value (DIFF_WC) is subtracted from the light current (R_WC) suitable for room temperature to obtain a light current (H_WC) suitable for room temperature.

On the other hand, the value of BER (BER_ct) that satisfies the minimum recording quality of the hard disk drive which is the determination standard in step S308 may vary depending on the recording capacity of the hard disk drive. This is because the track pitch varies according to the recording capacity, and the threshold of the write current at which WEAK WRITE can be expressed in a low capacity hard disk drive is higher than that of a high capacity hard disk drive.

In addition, the write current H_WC suitable for high temperature is preferably generated for each head and for each zone.

As described above, the method of optimizing the light current in the high temperature condition according to the present invention is not based on the optimal BER at high temperature but is suitable for high temperature based on BER (BER_ct) that satisfies the minimum recording quality of the hard disk drive. Setting the write current has the effect of satisfying the minimum recording quality even under conditions affecting the recording quality in a high temperature environment which is not considered in the burn-in test.

Claims (3)

Determining a light current (R_WC) suitable for room temperature and an overshoot current (H_OSC) suitable for high temperature based on an optimal bit error rate (BER); Using a random write current (WC) and the overshoot current (H_OSC) suitable for the high temperature, data is written to the tracks adjacent to the target track as many times as the temperature is suitable, and the data recorded in the target track is read to read the bit error rate ( Measuring BER); Checking whether the measured bit error rate BER satisfies a bit error rate BER_ct corresponding to a threshold value of a write current in which a weak write occurs; Repeating the process of measuring and checking the bit error rate (BER) while changing the value of the write current (WC) if the measured bit error rate (BER) does not satisfy the bit error rate (BER_ct) corresponding to the threshold value; And If the measured bit error rate (BER) satisfies the bit error rate (BER_ct) corresponding to the threshold value, setting the write current (WC) at this time to a write current (H_WC) suitable for high temperature of the hard disk drive How to set the light current suitable for high temperature. The write current of claim 1, wherein the bit error rate BER_ct corresponding to the threshold is greater than a bit error rate generated by a write current in which a weak write occurs. How to set up. The method of claim 1, And a bit error rate (BER_ct) corresponding to the threshold is variable according to the recording capacity of the hard disk drive, and the higher the recording capacity of the hard disk drive, the higher.

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