KR20060084119A - Method for calibrating of adc - Google Patents

Abstract

The present invention relates to a calibration method for compensating for errors due to a gain deviation of an analog-to-digital converter for converting a magnitude of a physical signal measured by a sensor to a desired measurement value.

In the calibration method of the ADC according to the present invention, the ADC is classified into a standard gain group having a standard gain, a high gain group having a gain higher than the standard, and a low gain group having a gain lower than the standard according to the gain size. ; Setting conversion equations corresponding to each of the classified groups; Converting an analog value into a digital value by the ADC and mapping the digitally converted value to a desired measurement value by a conversion equation corresponding to a group to which the ADC belongs; And calibrating the mapped measured value with reference to the group to which the ADC belongs.

The calibration method of the ADC according to the present invention has the effect of obtaining an accurate measurement value by compensating for the error of the measurement value due to the gain deviation of the ADC.

Description

Calibration Method for Analog-to-Digital Converters {Method for calibrating of ADC}

1 is a block diagram showing a conventional calibration device.

2 shows a configuration of a hard disk drive 10 to which the present invention is applied.

FIG. 3 is a block diagram illustrating an electrical circuit of the hard disk drive of FIG. 2.

4A and 4B show the configuration of the temperature sensor 260 and the temperature-output characteristic of the dummyster, respectively, shown in FIG. 2.

Figure 5 shows the relationship between the mapped temperature and the detected value of the dummyster.

6 is a flowchart illustrating a temperature measurement process in a hard disk drive.

7 is a flowchart illustrating a calibration method of an ADC according to the present invention.

FIG. 8 is a graph schematically illustrating a method of classifying ADCs according to gains in the calibration method illustrated in FIG. 7.

The present invention provides a method for mapping the magnitude of a physical signal measured by a sensor to a desired measurement value, which compensates for errors due to gain (amplification gain) deviation of an analog-to-digital converter that converts the magnitude of a physical signal into a digital value. It relates to a calibration method.

A hard disk drive, which is one of the data storage devices, plays back data recorded on the disk by the magnetic head or records user data on the disk.

Hard disk drives are very sensitive to environmental changes in recording data. The changing environmental factors must be accurately understood and reflected in the operation of the hard disk to prevent weak writes or adjacent track writes.

One of the environmental factors that affect the operation of hard disk drives is temperature. Temperature affects the coercive force of the disc, the disc expansion, and the like. As is well known, temperature is the most important factor in the optimization of read / write channel parameters of a hard disk.

Dummyster is used to detect the operating temperature of the hard disk drive. The hard disk drive digitally converts the output value of the dummyster to obtain the temperature value from the output value of the dummyster, and maps the digitally converted dummyster output value to the temperature value using a conversion equation. In this process, an analog-to-digital converter (ADC) is used to digitally convert the dummy output value.

ADCs have inherent offsets and gains. In other words, each ADC has a different offset and gain. Therefore, it is necessary to calibrate the ADC to produce a constant output for a constant input value.

1 is a block diagram showing a conventional calibration device. Referring to FIG. 1, a dummyster 102, an ADC 104, and a gain adjusting register 106 are shown. The gain adjusting register 106 is for compensating for the gain deviation of the ADC 104. In practice, the gain adjusting register 106 is implemented inside the ADC 104, but is drawn out of the ADC 104 for convenience of description.

The conventional calibration method is to adjust the gain corresponding to the output deviation of the ADC 104, i.e., the difference from the output of the standard to the input of the standard.

In practice, however, even if the gain of the ADC 104 is adjusted, it is difficult to calibrate so that the deviation between the ADCs falls within a predetermined range. Although the output deviation is reduced by adjusting the gain of the ADC 104, the output deviation is amplified again in the process of mapping the digital value converted by the ADC 104 to a desired measured value, for example, a temperature value, by a conversion equation. Because it appears.

An object of the present invention is to provide a calibration method for correcting a gain deviation of an ADC.

Another object of the present invention is to provide a recording medium on which a program for performing the above calibration method is recorded.

Calibration method of the ADC according to the present invention to achieve the above object

In the method of converting the magnitude of the physical signal measured by the sensor to a digital value through the desired ADC, and converting the converted digital value to the desired measurement value using a conversion equation,

Classifying the ADC into a standard gain group having a gain of a standard, a high gain group having a gain higher than a standard, and a low gain group having a gain lower than a standard according to a gain size;

Setting conversion equations corresponding to each of the classified groups;

Converting an analog value into a digital value by the ADC and mapping the digitally converted value to a desired measurement value by a conversion equation corresponding to a group to which the ADC belongs; And

And calibrating the mapped measured value with reference to the group to which the ADC belongs.

Here, the calibration process

In the case of the ADC of the upper gain group, the mapped measurement value is subtracted and output as much as the difference from the conversion result by the conversion equation corresponding to the standard gain group.

In the case of the ADC of the low gain group, and outputs by adding as much as the difference from the conversion result by the conversion equation corresponding to the standard gain group in the mapped measured value, and

In the case of the ADC of the standard gain group, the mapped measurement value is output.

In addition, the process of classifying ADCs according to the amount of gain

The reference input voltage corresponding to the offset, the first input voltage larger by k than the reference voltage, and the second input voltages larger by 2K than the reference voltage are applied to the ADC so that the reference output voltage and the first output corresponding to the respective input voltages are applied. Obtaining a voltage and a second output voltage;

Calculating a difference between the average of the reference output voltage and the second output voltage and the first output voltage; And

It is preferable to include the step of classifying the ADC according to the magnitude of the difference value.

A computer-readable recording medium according to the present invention for achieving the above another object is

In a recording medium that can be read by a computer, a method of converting the magnitude of a physical signal measured by a sensor into a digital value through a desired ADC and converting the converted digital value into a desired measurement value using a conversion equation,

Classifying the ADC into a standard gain group having a gain of a standard, a high gain group having a gain higher than a standard, and a low gain group having a gain lower than a standard according to a gain size;

Setting conversion equations corresponding to each of the classified groups;

Converting an analog value into a digital value by the ADC and mapping the digitally converted value to a desired measurement value by a conversion equation corresponding to a group to which the ADC belongs; And

The process of calibrating the mapped measured value with reference to the group to which the ADC belongs is recorded.

The features and advantages of the present invention will become apparent from the following detailed description of exemplary embodiments of the invention shown in the accompanying drawings.

Reference will be made in detail to exemplary embodiments of the invention, wherein like reference numerals denote like elements. In addition, in order to simplify the description, anything that is not novel or well known to those skilled in the art will be omitted.

2 shows a configuration of a hard disk drive 10 to which the present invention is applied. The hard disk drive 10 shown in FIG. 2 includes at least one magnetic disk 12 that is rotated by a spindle motor 14. Hard disk drive 10 also includes a transducer 16 located adjacent disk surface 18.

The transducer 16 can read or write information on the rotating disk 12 by sensing and magnetizing the magnetic field of each disk 12. Typically each transducer 16 is associated with a respective disk surface 18. On the other hand, although shown and described as a single transducer 16 in FIG. 1, in practice this consists of a write transducer for magnetizing the disc 12 and a separate read transducer for sensing the magnetic field of the disc 12. It should be understood that there is. Typically, write converters consist of magnetic circuits with voids, and read converters consist of Magneto-Resistive (MR) elements. The transducer 16 is also commonly referred to as a head.

The transducer 16 can be integrated into the slider 20. The slider 20 is structured to create an air bearing between the transducer 16 and the disk surface 18. The slider 20 is coupled to the head gimbal assembly 22. The head gimbal assembly 22 is attached to an actuator arm 24 having a voice coil 26. The voice coil 26 is located adjacent to the magnetic assembly 28 that specifies the voice coil motor 30 (VCM). The current supplied to the voice coil 26 generates a torque that rotates the actuator arm 24 relative to the bearing assembly 32. Rotation of actuator arm 24 will move transducer 16 across disk surface 18.

The information is typically stored in concentric circular tracks on the disc 12. Each track 34 generally includes a plurality of sectors. Each sector includes a data field and an identification field (also called a servo field). The identification field consists of a gray code identifying the sector and the track (cylinder), and burst signals for detecting the extent to which the transducer 16 deviates from the track center. The transducer 16 is moved across the disk surface 18 by the movement of the actuator arm.

FIG. 3 is a block diagram illustrating an electrical circuit of the hard disk drive of FIG. 2.

The hard disk drive shown in FIG. 3 includes a disk 12, a converter 16, a preamplifier 210, a write / read channel 220, a host interface 230, a controller 240, a memory 250, and a temperature. The sensor 260 and the voice coil motor (VCM) driver 270 are provided.

The circuit configuration including the preamplifier 210 and the write / read channel 220 above will be referred to as a write / read circuit.

The memory 250 stores various programs and data for controlling the hard disk drive. In particular, the retry table and previous retry information are stored to execute the retry control method according to an exemplary embodiment of the present invention. In this case, the memory 250 is designed as a nonvolatile memory.

The retry table stores parameter values to ensure optimal performance of the hard disk drive.

First, the operation of a general hard disk drive will be described.

In the data read mode, the hard disk drive amplifies the electrical signal sensed by the converter 16 (also called a head) from the disk 12 in the preamplifier 210 to facilitate signal processing. Then, in the recording / reading channel 220, the amplified analog signal is encoded into a digital signal that can be read by a host device (not shown), converted into stream data, and transmitted to the host device through the host interface 230. send.

In contrast, in the data write mode, the hard disk drive receives data from a host device and temporarily stores the data in a buffer (not shown) embedded in the host interface 230, and sequentially outputs the data stored in the buffer. The write / read channel 220 converts the write current amplified by the preamplifier 210 to the disk 12 via the converter 16 after conversion into a binary data stream suitable for the write channel.

The controller 240 may be a digital signal processor (DSP), a microprocessor, a microcontroller, or the like. The controller 240 supplies a control signal to the write / read channel 220 to read from or write information to the disk 12. Information is typically sent from the R / W channel to the host interface circuit 2320. The host interface circuit 230 includes a buffer memory and control circuitry that allows a hard disk drive to interface to a system such as a personal computer.

The controller 240 is also coupled to the VCM drive circuit 270 which supplies a drive current to the voice coil 26. The controller 240 supplies a control signal to the VCM driving circuit 270 to control the excitation of the VCM and the movement of the transducer 16.

The controller 240 is coupled to a nonvolatile memory device 250 such as a flash memory device. The memory device 250 stores instructions and data used by the controller 240 to execute a software routine. One software routine is a seek routine that moves the transducer 16 from one track to another. The seek routine includes a server control routine to ensure that the transducer 16 is moved to the correct track.

In addition, when the temperature detection is required, the controller 240 approximates and uses the detected value from the temperature sensor 260 according to the actual temperature using the polynomial stored in the memory 250. A typical case where temperature detection is required is to optimize the read / light channel parameters.

4A and 4B show the configuration of the temperature sensor 260 and the temperature-output characteristic of the dummyster, respectively, shown in FIG. 2. The higher the temperature, the lower the output value, and the lower the temperature, the higher the output value. That is, the characteristics of the dummy 262 is not linear with respect to temperature.

Figure 5 shows the relationship between the mapped temperature and the detected value of the dummyster. In FIG. 5, the vertical axis | shaft shows a temperature and the horizontal axis shows a detection value of a dummyster. In addition, what is shown by the thick solid line in FIG. 5 shows the result approximated by a polynomial.

6 is a flowchart illustrating a temperature estimation process in a hard disk drive.

When a temperature change occurs, the resistance value of the temperature sensor 260 changes, so that the voltage value Vout applied to the temperature sensor 260 in FIG. 3A fluctuates.

The voltage value Vout detected by the temperature sensor 260 is converted into a digital value by the ADC 264 and provided to the controller 240. The controller 240 estimates the temperature of the digital value converted by the ADC 264 using a conversion equation. Here, the conversion equation corresponds to the polynomial described with reference to FIG.

7 is a flowchart illustrating a calibration method of an ADC according to the present invention, and shows an example of measuring a temperature in a hard disk drive.

First, the ADC is classified into three groups according to the gain. (S702) The ADC has a gain of the standard (standard gain group), a gain higher than the standard (high gain group), and a gain lower than the standard. Can be classified into those having a low gain group.

Transforms corresponding to the classified groups are set (s704). That is, transforms corresponding to the high gain group, the standard gain group, and the low gain group are set. Here, the conversion equation is set in consideration of the gain of the polynomial and the ADC described with reference to FIG.

The analog value is converted into a digital value by the ADC, and the digital converted value is mapped to a desired measurement value by a conversion formula corresponding to the group to which the ADC belongs. (S706) For example, a high gain group ADC The conversion formula set for the gain group maps to the desired measured value, for example the temperature value.

The mapped measurement value is calibrated by referring to the group to which the ADC belongs (s708).

FIG. 8 is a graph schematically illustrating a method of classifying ADCs according to gains in the calibration method illustrated in FIG. 7, and illustrates output curves of the ADCs showing output voltages according to input voltages. In Fig. 5 three output characteristic curves f1, f2, f3 are shown. Among these, f2 is an output characteristic curve of an ADC having standard gain, and f1 and f2 are output characteristic curves of an ADC having gains higher or lower than the standard gain, respectively.

Among the input voltages, VI_ref is a reference input voltage corresponding to an offset, VI_1 is a first input voltage higher by k than the reference input voltage VI_ref, and VI_2 is a second input voltage higher by 2k than the reference input voltage VI_ref. Also, among the output voltages, VO_ref is a reference output voltage corresponding to an offset, VO_1 is a first output voltage corresponding to the first input voltage VI_1, and VO_2 is a second output voltage corresponding to the second input voltage VI_2. Here, it is preferable that the first input voltage VI_1 and the second input voltage VI_2 are selected to be larger as possible within the dynamic range of the ADC.

Referring to the output characteristic curve (f2) of the ADC belonging to the standard gain group,

The relationship of (VO_2 VO_ref) / 2 = VO_1 is maintained.

However, referring to the output characteristic curve f1 of the ADC belonging to the high gain group,

(VO_2 VO_ref) / 2> VO_1

Conversely, referring to the output characteristic curve (f3) of the ADC belonging to the low gain group,

(VO_2 VO_ref) / 2 <VO_1.

That is, it is possible to determine what gain characteristics the ADC has based on the difference between (VO_2 VO_ref) / 2 and VO_1.

For example, if (VO_2 VO_ref) / 2-VO_1 = error count

if error count> 10, then ADC with higher gain than standard

if error count <= 10 and error count> -10, then ADC with standard gain

if error count <-10, then ADC with higher gain than standard

Can be classified as

In the conversion equation setting process s704 illustrated in FIG. 7, conversion equations corresponding to each of the classification groups of the ADC are set.

When x is the digital conversion value of the ADC, the conversion formula y1 for the ADC having a gain higher than the standard, the conversion formula y2 for the ADC having a gain higher than the standard, and the conversion formula y3 for the ADC having a lower gain than the standard are defined as follows. do.

y1 = f_high_gain_conversion (x)

y2 = f_middle_gain_conversion (x)

y3 = f_low_gain_conversion (x)

For example, in case of ADC belonging to the standard gain group, the result of ADC conversion by the conversion formula y2 is mapped to the measured value. Here, y1 to y3 are conversion equations set according to the polynomial and the gain of the ADC described with reference to FIG. 5.

However, mapping values are not yet correctly calibrated. Although different conversion equations are applied in consideration of gain difference of ADC, the conversion result by y1 and y3 does not exactly match the conversion result by y2.

In the calibration process s708 illustrated in FIG. 7, the measured value compensated for the gain deviation is obtained by compensating the mapped measured value to be the measured value by the ADC having standard gain.

Specifically, the ADC that belongs to the high gain group compensates by subtracting y1-y2 from the result converted by y1, and the ADC that belongs to the lower gain group adds y2-y3 from the result converted by y3. If the ADC belongs to the standard gain group, the result converted by y2 is used as it is. In other words, accurate calibration is achieved by compensating the result transformed by y1 and y3 to match the result transformed by y2.

Here, y2-y3 represents the difference between the result by the y2 conversion formula and the result by the y3 conversion formula.

The invention can be practiced as a method, apparatus, system, or the like. When implemented in software, the constituent means of the present invention are code segments that necessarily perform the necessary work. The program or code segments may be stored in a processor readable medium or transmitted by a computer data signal coupled with a carrier on a transmission medium or network. Processor readable media includes any medium that can store or transmit information. Examples of processor-readable media include electronic circuits, semiconductor memory devices, ROMs, flash memory, erasable ROM (EROM), floppy disks, optical disks, hard disks, optical fiber media, radio frequency (RF) networks, Etc. Computer data signals include any signal that can propagate over transmission media such as electronic network channels, optical fibers, air, electromagnetic fields, RF networks, and the like.

Specific embodiments shown and described in the accompanying drawings are only to be understood as an example of the present invention, not to limit the scope of the invention, but also within the scope of the technical spirit described in the present invention in the technical field to which the present invention belongs As various other changes may occur, it is obvious that the invention is not limited to the specific constructions and arrangements shown or described. That is, it is a matter of course that the present invention can be applied not only to various disk drives including hard disk drives, but also to various kinds of data storage devices.

 As described above, the calibration method of the ADC according to the present invention has the effect of obtaining an accurate measurement value by compensating for the error of the measurement value due to the gain deviation of the ADC.

Claims (4)

In the method of converting the magnitude of the physical signal measured by the sensor to a digital value through the desired ADC, and converting the converted digital value to the desired measurement value using a conversion equation, Classifying the ADC into a standard gain group having a gain of a standard, a high gain group having a gain higher than a standard, and a low gain group having a gain lower than a standard according to a gain size; Setting conversion equations corresponding to each of the classified groups; Converting an analog value into a digital value by the ADC and mapping the digitally converted value to a desired measurement value by a conversion equation corresponding to a group to which the ADC belongs; And And calibrating the mapped measured value with reference to the group to which the ADC belongs. The method of claim 1, wherein the calibration process In the case of the ADC of the upper gain group, the mapped measurement value is subtracted and output as much as the difference from the conversion result by the conversion equation corresponding to the standard gain group. In the case of the ADC of the low gain group, and outputs by adding as much as the difference from the conversion result by the conversion equation corresponding to the standard gain group in the mapped measured value, and In the case of the ADC of the standard gain group, the calibration method characterized in that to output the mapped measured value. The process of claim 1, wherein the classifying of the ADC according to the magnitude of the gain is performed. The reference input voltage corresponding to the offset, the first input voltage larger by k than the reference voltage, and the second input voltages larger by 2K than the reference voltage are applied to the ADC so that the reference output voltage and the first output corresponding to the respective input voltages are applied. Obtaining a voltage and a second output voltage; Calculating a difference between the average of the reference output voltage and the second output voltage and the first output voltage; And And classifying the ADC according to the magnitude of the difference value. In a recording medium that can be read by a computer, a method of converting the magnitude of a physical signal measured by a sensor into a digital value through a desired ADC and converting the converted digital value into a desired measurement value using a conversion equation, Classifying the ADC into a standard gain group having a gain of a standard according to a gain size, a high gain group having a gain higher than a standard, and a low gain group having a gain lower than a standard; Setting conversion equations corresponding to each of the classified groups; Converting an analog value into a digital value by the ADC and mapping the digitally converted value to a desired measurement value by a conversion equation corresponding to a group to which the ADC belongs; And And a process of calibrating the mapped measured value with reference to the group to which the ADC belongs.

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