Head gimbal assembly height determination using charge / voltage converter

Abstract

The invention relates to a head gimbal assembly height determination using a charge / voltage converter. A circuit for determining a head gimbal assembly (HGA) height is provided. The circuit includes a first switch configured to be controlled by a first clock signal; an amplifier; and a first capacitor coupled to the first switch, where the first capacitor is formed from at least a portion of a head gimbal assembly and a storage medium. The circuit further includes a second capacitor coupled to an input of the amplifier and an output of the amplifier, where the second capacitor is configured to store charge from the first capacitor during one or more cycles of the first clock signal. The amplifier is configured to generate an output voltage based at least in part on a change in capacitance of the first capacitor over the one or more cycles of the first clock signal.

Description

[0001] Copyright Notice

[0002] A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document and the patent disclosure as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. Technical Field

[0003] The present disclosure generally relates to methods, systems, and apparatus for head gimbal assembly height determination in a hard disk drive. Background Art

[0004] The height of the head gimbal assembly (HGA) is generally determined by the capacitance (C) between the HGA and the underlying media (e.g., storage media such as hard drive platters or other magnetic storage media). hga ). The height of the HGA can be determined by measuring the change in capacitance using capacitive height sensing (CHS), which refers to the relative position of the HGA above (or below) the media. Therefore, by measuring the capacitance shift (C delta ) to determine the proximity of the HGA to the disk. delta For the small capacitors involved in the measurement, process, voltage, and temperature (PVT) variations can introduce inconsistencies.

[0005] Thus, methods, systems, and apparatus for more robust HGA height determination are provided. Summary of the invention

[0006] In one aspect, the present disclosure provides an apparatus comprising: a first circuit comprising: a first switch configured to be controlled by a first clock signal, the first switch comprising a first terminal and a second terminal; an amplifier comprising an inverting input, a non-inverting input, and an output, wherein the inverting input is coupled to the second terminal; a first capacitor coupled to the first terminal of the first switch, wherein the first capacitor is formed between a head gimbal assembly and a medium; and a second capacitor comprising a third terminal and a fourth terminal, the third terminal being coupled to the inverting input of the amplifier, and the fourth terminal being coupled to the output of the amplifier, wherein the second capacitor is configured to store charge from the first capacitor during one or more cycles of the first clock signal, wherein the amplifier is configured to generate an output voltage based at least in part on a change in capacitance of the first capacitor during the one or more cycles of the first clock signal.

[0007] On the other hand, the present disclosure provides a system comprising: a head gimbal assembly; a storage medium, wherein a capacitance is formed between at least a portion of the head gimbal assembly and the storage medium; and a circuit configured to determine a height of the head gimbal assembly relative to the storage medium, the circuit comprising: a first subcircuit comprising: a first switch configured to be controlled by a first clock signal, the first switch comprising a first terminal and a second terminal; an amplifier comprising an inverting input, a non-inverting input, and an output, wherein the inverting input is coupled to the second terminal; a first capacitor coupled to the first terminal of the first switch, wherein the first capacitor is formed by at least a portion of the head gimbal assembly and the storage medium; and a second capacitor comprising a third terminal and a fourth terminal, the third terminal coupled to the inverting input of the amplifier, and the fourth terminal coupled to the output of the amplifier, wherein the second capacitor is configured to store charge from the first capacitor during one or more cycles of the first clock signal, wherein the amplifier is configured to generate an output voltage based at least in part on a change in capacitance of the first capacitor during the one or more cycles of the first clock signal.

[0008] On the other hand, the present disclosure provides a circuit comprising: a first switch configured to be controlled by a first clock signal, the first switch comprising a first terminal and a second terminal; an amplifier comprising an inverting input, a non-inverting input and an output, wherein the inverting input is coupled to the second terminal; a first capacitor coupled to the first terminal of the first switch, wherein the first capacitor is formed by at least a portion of a head gimbal assembly and a storage medium; and a second capacitor comprising a third terminal and a fourth terminal, the third terminal being coupled to the inverting input of the amplifier and the fourth terminal being coupled to the output of the amplifier, wherein the second capacitor is configured to store charge from the first capacitor during one or more cycles of the first clock signal, wherein the amplifier is configured to generate an output voltage based at least in part on a change in capacitance of the first capacitor during the one or more cycles of the first clock signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] A further understanding of the nature and advantages of particular embodiments may be achieved by reference to the remainder of the specification and drawings, wherein like reference numerals are used to refer to like components. In some instances, a sub-label is associated with a reference numeral to denote one of multiple similar components. When reference is made to a reference numeral without specifying an existing sub-label, it is intended to refer to all such multiple similar components.

[0010] Figure 1 is a schematic block diagram of a control system for an HGA according to various embodiments;

[0011] Figure 2 is a schematic diagram of a circuit for HGA height determination according to various embodiments; and

[0012] Figure 3 is a timing diagram of various signals in a circuit for HGA height determination according to various embodiments. DETAILED DESCRIPTION

[0013] Various embodiments describe an apparatus for more robust HGA height determination utilizing a charge-to-voltage converter.

[0014] In some embodiments, an apparatus for HGA height determination is provided. The apparatus includes a first circuit configured to convert a charge into a voltage. The first circuit includes; a first switch configured to be controlled by a first clock signal, the first switch including a first terminal and a second terminal; an amplifier including an inverting input, a non-inverting input, and an output, wherein the inverting input is coupled to the second terminal; and a first capacitor coupled to the first terminal of the first switch. The first capacitor may be formed between a head gimbal assembly and a medium. The first circuit further includes a second capacitor, the second capacitor including a third terminal and a fourth terminal, the third terminal being coupled to the inverting input of the amplifier, and the fourth terminal being coupled to the output of the amplifier. The second capacitor may be configured to store a charge from the first capacitor over one or more cycles of the first clock signal. The amplifier may be configured to generate an output voltage based at least in part on a change in capacitance of the first capacitor over the one or more cycles of the first clock signal.

[0015] In some embodiments, a system for HGA height determination is provided. The system includes a head gimbal assembly and a storage medium. A capacitance may be formed between at least a portion of the head gimbal assembly and the storage medium. The system further includes a circuit configured to determine the height of the head gimbal assembly relative to the storage medium. The circuit includes a first subcircuit configured to convert a charge into a voltage. The first subcircuit includes: a first switch configured to be controlled by a first clock signal, the first switch including a first terminal and a second terminal; an amplifier including an inverting input, a non-inverting input, and an output, wherein the inverting input is coupled to the second terminal; and a first capacitor coupled to the first terminal of the first switch. The first capacitor may be formed by at least a portion of the head gimbal assembly and the storage medium. The first circuit further includes a second capacitor, the second capacitor including a third terminal and a fourth terminal, the third terminal coupled to the inverting input of the amplifier, and the fourth terminal coupled to the output of the amplifier. The second capacitor may be configured to store charge from the first capacitor during one or more cycles of the first clock signal. The amplifier may be configured to generate an output voltage based at least in part on a change in capacitance of the first capacitor over the one or more cycles of the first clock signal.

[0016] In a further embodiment, a charge / voltage converter circuit for HGA height determination is provided. The circuit includes: a first switch configured to be controlled by a first clock signal; an amplifier; and a first capacitor coupled to the first switch, wherein the first capacitor is formed by at least a portion of a head gimbal assembly and a storage medium. The circuit further includes a second capacitor coupled to an input of the amplifier and an output of the amplifier, wherein the second capacitor is configured to store charge from the first capacitor over one or more cycles of the first clock signal. The amplifier is configured to generate an output voltage based at least in part on a change in capacitance of the first capacitor over the one or more cycles of the first clock signal.

[0017] In the following description, for the purpose of explanation, numerous details are set forth to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art that other embodiments may be practiced without some of these details. Several embodiments are described herein, and although various features are attributed to different embodiments, it should be understood that features described with respect to one embodiment may also be combined with other embodiments. However, for the same reasons, it should not be considered that a single or multiple features of any described embodiment are essential to every embodiment of the present invention, as other embodiments of the present invention may omit such features.

[0018] When an element is referred to herein as being "connected" or "coupled" to another element, it is understood that the element may be directly connected to the other element, or that there may be intervening elements between the elements. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, it is understood that there may be no intervening elements in the "direct" connection between the elements. However, the presence of a direct connection does not exclude other connections where there may be intervening elements.

[0019] When an element is referred to herein as being "disposed" in a certain manner relative to another element (e.g., disposed on, disposed between, disposed below, disposed adjacent to, or disposed in some other relative manner), it is understood that the element may be disposed directly relative to the other element (e.g., disposed directly on the other element) or that there may be intervening elements between the elements. In contrast, when an element is referred to as being "directly disposed" relative to another element, it is understood that there are no intervening elements in the "direct" instance. However, the presence of a direct placement does not exclude other instances in which there may be intervening elements.

[0020] Similarly, when an element is referred to herein as a "layer," it is understood that the layer may be a single layer or include multiple layers. For example, a conductive layer may include multiple different conductive materials or multiple layers of different conductive materials, and a dielectric layer may include multiple dielectric materials or multiple layers of dielectric materials. When a layer is described as being coupled or connected to another layer, it is understood that the coupled or connected layer may include intervening elements present between the coupled or connected layers. In contrast, when a layer is referred to as being "directly" connected or coupled to another layer, it is understood that there are no intervening elements between the layers. However, the presence of a directly coupled or connected layer does not exclude other connections in which intervening elements may be present.

[0021] In addition, the terms left, right, front, back, top, bottom, forward, reverse, clockwise, and counterclockwise are used for explanation purposes only and are not limited to any fixed direction or orientation. Instead, they are only used to indicate the relative position and / or direction between the various parts of an object and / or component.

[0022] In addition, for ease of description, the methods and processes described herein may be described in a particular order. However, it should be understood that unless the context indicates otherwise, intervening processes may occur before and / or after any portion of the described process, and various other procedures may be reordered, added, and / or omitted according to various embodiments.

[0023] Unless otherwise indicated, all numbers used herein to indicate quantities, dimensions, and the like are to be understood as being modified in all instances by the term "about". In this application, the use of the singular includes the plural unless otherwise specifically indicated, and the use of the terms "and" and "or" means "and / or" unless otherwise indicated. In addition, the use of the terms "including" and "having" and other forms such as "includes", "included", "has", "have" and "had" should be considered non-exclusive. In addition, terms such as "element" or "component" encompass elements and components comprising one unit and elements and components comprising more than one unit, unless otherwise specifically indicated.

[0024] As used herein, the phrase "at least one of ..." preceding a series of items (where the terms "and" or "or" are used to separate any of the items) modifies the list as a whole, rather than each member of the list (i.e., each item). The phrase "at least one of ..." does not require selection of at least one of each of the listed items; in contrast, the phrase allows for a meaning that includes at least one of any of the items and / or at least one of any combination of items. By way of example, the phrase "at least one of A, B, and C" or "at least one of A, B, or C" each refers to only A, only B, or only C; and / or any combination of A, B, and C. Where it is desired to select "at least one of each of A, B, C," or alternatively "at least one of A, at least one of B, and at least one of C," it is so explicitly described.

[0025] The height of the HGA affects the capacitance (C) formed between the HGA and the dielectric (also interchangeably referred to as the disk). hga ). As the HGA gets closer to the disk, C hga Thus, the height of the HGA refers to the position of the HGA above and / or below the underlying dielectric. The HGA height refers to the distance between the HGA and the underlying dielectric (e.g., how high above the dielectric and / or how far below the underlying dielectric). Typically, the HGA height can be measured by measuring the change in capacitance C delta However, due to C delta Very small (for example, C hga Changes < 1.5%), making it difficult to measure small capacitance changes across PVT variations.

[0026] Conventional methods for HGA height determination utilize relaxation oscillators, where the capacitance C between the HGA and the dielectric hga Continuously charge and discharge within the threshold voltage range. hgaAs the oscillation period increases, the time to complete a charge and discharge cycle also increases. Therefore, C hga Therefore, the performance is very important for detecting C hga The stability and accuracy of the oscillator period are sensitive to small changes in PVT. However, the relaxation oscillator spans PVT variations and is sensitive to comparator jitter. In addition, a long dwell time relative to the switched capacitor charge / voltage converter described herein (e.g., approximately 1000 cycles are required to achieve 0.1% resolution) is utilized for each measurement in order to allow small changes in the oscillation period to accumulate to a detectable value, which increases head wear.

[0027] The proposed HGA height sensing architecture is described in the following embodiments. Specifically, a discrete-time switched capacitor charge / voltage converter is used to measure C delta Specifically, the changes stored in C hga The amount of charge in the oscillator is converted to a proportional voltage, which is then compared to a threshold voltage or digitized via an ADC. By utilizing a charge / voltage converter instead of an oscillator, altitude determination becomes less sensitive to timing and PVT variations.

[0028] Figure 1 1 is a schematic block diagram of a control system 100 for an HGA assembly. The control system 100 may include a control logic 105, an actuator 110, an actuator arm 115, an HGA 120, and an HGA height sensing circuit 125. Figure 1 The system 100 is schematically illustrated in FIG. 1 , and the various elements and other arrangements of the system 100 may be modified according to various embodiments.

[0029] In various embodiments, the control system 100 may be more generally configured to control a head stack assembly (HSA) of a hard disk drive (HDD). In some examples, control of the HSA may include adjusting the height of the HGA 120 via the control logic 105. Specifically, the distance between the HGA 120 and the underlying media (e.g., a hard disk drive platter) may be adjusted based on determining the height of the HGA 120 (or a change in the height of the HGA 120) via the HGA height sensing circuit 125, as described below with respect to Figure 2 Describe in more detail.

[0030] Thus, in various embodiments, the control logic 105 can be configured to control the actuator 110, which causes movement of the actuator arm 115. The control logic 105 can include hardware, software, or a combination of hardware and software. In various examples, the control logic 105 can be configured to generate control signals that can drive or otherwise actuate the actuator 110. In some examples, the control logic 105 can be configured to control an elevator function (e.g., vertical position control) of the HGA 120 via upward and / or downward movement of the actuator arm 115.

[0031] In various examples, the actuator 110 may include, but is not limited to, a voice coil actuator (e.g., a permanent magnet and coil actuator), a moving magnetic actuator, a shape memory alloy (SMA) actuator, a piezoelectric, a thermal, or other suitable actuator. The actuator 110 may be configured to move an actuator arm 115. The actuator arm 115 may be coupled to the actuator 110 at a first end (e.g., a proximal end) via a pivot bearing or other swaged connection. The HGA 120 may in turn be coupled to an opposite end of the actuator arm 115 (e.g., a distal end of the actuator arm 115 away from the connection with the actuator 110). In various examples, the HDD may include one or more disks. The respective actuator arms 115 and the respective HGAs 120 may be disposed on (e.g., above) and / or under (e.g., below) each respective disk of the one or more disks.

[0032] In various embodiments, the position (or position change) of the HGA 120 may be determined by the HGA height sensing circuit 125 and provided as feedback to the control logic 105 for adjusting the position of the HGA 120. Figure 2 Details of the HGA height sensing circuit 125 are provided.

[0033] Figure 2 2 is a schematic diagram of a circuit 200 for HGA height determination according to various embodiments. The circuit 200 includes a first switch 205, a second switch 210, a first capacitor 215, an HGA capacitor (C hga ) 220, amplifier 225, reset switch 260 and filter capacitor 265, which together form the charge / voltage converter subcircuit 230. The circuit further includes a third switch 235 and a fourth switch 240, an offset voltage (voff) 245 and an offset capacitor 250, which together may be referred to as an offset subcircuit 255. The circuit 200 further includes a comparator 270 and an analog / digital converter (ADC) 275. It should be noted that in Figure 2 Circuit 200 is schematically illustrated in FIG. 2 , and various elements and other arrangements of circuit 200 may be modified according to various embodiments.

[0034] In contrast to conventional methods, the circuit 200 for HGA height determination utilizes a charge / voltage converter subcircuit 230 and an offset subcircuit 255 to measure changes in capacitance instead of a relaxation oscillator. In addition to allowing charge to accumulate over multiple cycles, changes in capacitance can be amplified via amplifier 225 by using a larger voltage vpos and a smaller filter capacitor 265, thereby allowing height detection to be more accurate. Furthermore, the charge / voltage converter subcircuit 255 is insensitive to PVT changes and parasitic components.

[0035] Thus, a discrete-time switched capacitor charge / voltage converter configured to measure the change in capacitance between the HGA and the underlying dielectric is provided. Specifically, the voltage is determined using the charge stored by the capacitor during a first discrete time period (e.g., one or more cycles of a clock signal, such as CLK and / or CLK2). Thus, the circuit 200 is configured to determine the position of the HGA based on the change in voltage between one or more consecutive discrete time periods.

[0036] In various embodiments, the capacitance between the HGA and the disk is represented by a variable capacitor C hga 220. In various examples, C can be measured at the signal pad of the HGA hga As used herein, a pad refers to a signal pad of a circuit, such as, but not limited to, an input / output pad, a pad, or other conductive structure within a circuit from which a signal can be measured or input. The parasitic capacitance C of the HGA par The first switch 205 is controlled by the first clock signal "CLK". The second switch 210 is controlled by the second clock signal "CLK2". The voltage at the first capacitor 215 and the HGA pad 220 is referred to as "vcap". The offset subcircuit 255 includes a third switch 235, a fourth switch 240 and an offset capacitor (C off ) 250. The third switch 235 is controlled by CLK like the first switch 205. The fourth switch 240 is controlled by CLK2 like the second switch 210.

[0037] In operation, the charge / voltage converter subcircuit 230 may be an integrator, wherein the amplifier 225 outputs a voltage (vinteg) that is proportional to the integrated value of the total charge applied to the inverting input of the amplifier 225. Thus, C hga The charge stored at 220 may be converted into an output signal vinteg. In various embodiments, amplifier 225 may include an inverting input and a non-inverting input. The terms "inverting" and "non-inverting" refer to the pin configuration of the amplifier, where the inverting input refers to the (-) or "negative" terminal of the amplifier, and the non-inverting input refers to the (+) or "positive" terminal of the amplifier. Therefore, the terms "inverting" and "non-inverting" are used as a naming convention to distinguish the terminals of the amplifier.

[0038] In various embodiments, circuit 200 may further include an offset subcircuit 255. Offset subcircuit 255 may be configured to remove the hga 220 is a constant charge injected into amplifier 225. Specifically, in some examples, C off 250 can be configured to hga 220 removes the constant charge, so that only the capacitance C delta The change that causes vinteg (V delta ). For example, as follows Figure 2 In more detail, when the second switch 210 and the fourth switch 240 are enabled via CLK2, the hga The charge of 220 is offset by capacitor C when the first voltage polarity is applied. off 250 is discharged (eg, removed). In some embodiments, when a second voltage polarity (opposite to the first voltage polarity) is applied, the opposite may occur, where C hga 220 removes the charge from amplifier 225 and C off 250 to C hga 220 replenishes the constant charge.

[0039] In various instances, due to C delta The voltage change caused by multiple charge injections (for example, from C hga 220 to amplifier 225) cycle, to the increase of charging voltage (vpos) and / or by using a smaller filter capacitor C filter 265 to amplify. Based on vinteg, detection of the HGA height can be determined. For example, in some embodiments, comparator 270 can be configured to compare vinteg with a threshold voltage (vthresh) to determine whether vinteg exceeds vthresh. By counting the number of cycles that vinteg exceeds vthresh, a change in the height of the HGA can be determined. In some further examples, ADC 275 can be configured to generate a digital output (dout) based on vinteg. Thus, a change in vinteg can be digitally determined based on a change in dout.

[0040] In various embodiments, the change in capacitance can be calculated as follows. hga1 As the capacitance of the HGA at the first position, and C hga2 As the capacitance of the HGA at the second position, C is given by hga2 :

[0041] C hga2 =C hga1 +cdelta Equation 1

[0042] At the first position, the measured voltage (vinteg1) can be given by:

[0043]

[0044] At the second position, the measured voltage (vinteg2) can be given as:

[0045]

[0046] Therefore, by measuring v delta To determine C delta , where v delta =vinteg2-vinteg1. Therefore, v delta It can be given by the following equation:

[0047]

[0048] Therefore, in various examples, it can be based on v delta To determine the change in capacitance, v delta The output "vout" of the comparator 270 and / or the digital output dout of the ADC 275 may be determined at least in part based on the output "vout" of the comparator 270 and / or the digital output dout of the ADC 275. In some examples, the output of the comparator 270 may indicate, for example, whether the change in the height of the HGA has exceeded a threshold distance (e.g., whether the HGA has moved a threshold amount). In other examples, the output dout of the ADC 275 may indicate a change in the height of the HGA. Alternatively, dout may be associated with the position of the HGA.

[0049] In various examples, the charge / voltage converter subcircuit 230 can be a discrete-time switched capacitor charge / voltage converter. hga The change is small, so the voltage difference V delta The conversion is also very small. In order to amplify V delta , multiple charge / voltage conversions can be performed each time the HGA height is measured. For each charge / voltage conversion, filter 265 accumulations by C hga 220 injected charge. Specifically, C filter 265 may have a first terminal coupled to the inverting input of amplifier 225 and a second terminal coupled to the output of amplifier 225. In this manner, C filter 265 may be configured to accumulate (e.g., within n cycles of CLK and / or CLK2) the hga 220. Therefore, after n conversions, V delta is amplified n times (for example, n*V deltaAfter each measurement, the reset switch 260 can be used to reset the value stored in C filter 265 in charge.

[0050] In various embodiments, the dynamic range of the charge / voltage converter subcircuit 230 may be increased via the offset subcircuit 255. By applying a constant offset voltage to C off 250 pre-charge, voff 245, C off 250 available from C hga 220 removes the fixed charge. In some examples, C off 250 can be configured to remove the hga 220 injected into C filter Therefore, as used herein, fixed charge refers to a charge that does not change between clock cycles of CLK and / or CLK2 and is determined by C off 250 from C hga 220. Therefore, the fixed charge is removed from C hga 220 The amount of fixed charge removed. In order to determine C delta , instead of C hga The absolute value of C can be removed in this way hga This allows a more sensitive determination of the charge injected by C delta In some alternative embodiments, as an offset capacitor C off Instead of (or in addition to) 250, offset subcircuit 255 may utilize other methods of removing charge, such as a constant current source.

[0051] For example, if C delta =C hga 1% of 220 will be provided by C hga +C delta The stored charge is converted into a voltage, then C delta Change the part of the vinteg (for example, V delta ) will only be about 1% of vinteg. However, if off 250 removed by C hga 220 stores 98% of the charge, then the charge / voltage conversion will be 0.02*C hga +C delta The stored charge is converted into a voltage. Therefore, V delta will be 33% of the vinteg, thereby converting the circuit to C delta The sensitivity is increased by 33 times.

[0052] Therefore, in some examples, the filter 265 to enlarge Chga Small changes (e.g., small C delta ) to improve accuracy. In addition, changes in vinteg (e.g., v delta ) is insensitive to parasitic capacitance and PVT changes. par ) and clock feedthrough (e.g., CLK and / or CLK2) can result in a constant offset that can be calibrated, for example, via offset subcircuit 255. Additionally, metal-to-metal (MOM) capacitors, such as those formed between the HGA and the underlying dielectric, have low voltage and temperature coefficients. In further embodiments, the dwell time of the measurement can be reduced relative to conventional techniques, thereby also reducing head wear.

[0053] In another example, the accuracy of the clock signal (e.g., CLK and / or CLK2) may not be so critical to a high degree of certainty, as long as the circuit 200 is stable before the next charging cycle, thereby allowing for more robust operation. In addition, since the circuit 200 does not rely on a high-speed accurate oscillator, power consumption may also be reduced. In another example, since a constant voltage is applied to the inverting input of the amplifier 225, leakage reduction techniques may be implemented.

[0054] In an alternative embodiment, an alternative method may include directly crossing C when the HGA height changes hga Make direct voltage measurements. C hga The change in capacitance will cause the hga In other embodiments, the circuit 100 may be implemented in other contexts for detecting small changes in capacitance. For example, in other embodiments, the circuit 100 may be implemented as part of various systems including, but not limited to, a touch sensor, a pressure switch, or a strain gauge.

[0055] Figure 3 is a timing diagram of the analog signal 300 of the circuit 200. Specifically, C hga From 10.0pF to 10.2pF, this is a change of 2% or 0.2pF. As can be seen from the timing diagram, Figure 2 The circuit 200 more robustly detects small changes in capacitance and measures them as a voltage.

[0056] Specifically, Figure 3 Description vout 305, vinteg 310 and C hga Changes over time. As the capacitance C hga 315 increases, the conversion voltage vinteg 310 reflects C hga315. When vinteg 310 reaches threshold voltage Vthresh at time t1, output signal Vout (eg, output signal Vout of comparator 270) may be asserted, which corresponds to a threshold height (eg, a threshold change in height) of HGA.

[0057] Although some features and aspects have been described with respect to embodiments, those skilled in the art will recognize that numerous modifications are possible. For example, the methods and processes described herein may be implemented using hardware components, custom integrated circuits (ICs), programmable logic, and / or any combination thereof. In addition, although the various methods and processes described herein may be described with respect to specific structural and / or functional components for ease of description, the methods provided by the various embodiments are not limited to any specific structural and / or functional architecture, but may be implemented in any suitable hardware configuration. Similarly, although some functionality is attributed to one or more system components, unless the context indicates otherwise, according to several embodiments, this functionality may be distributed among various other system components.

[0058] In addition, although the procedures of the methods and processes described herein are described in a particular order for ease of description, various procedures may be reordered, added, and / or omitted according to various embodiments unless the context indicates otherwise. In addition, the procedures described with respect to a method or process may be incorporated into other described methods or processes; similarly, system components described according to a particular structural architecture and / or with respect to one system may be organized in an alternative structural architecture and / or incorporated into other described systems. Therefore, although various embodiments are described with or without some features for ease of description and explanation of aspects of the embodiments, various components and / or features described herein with respect to specific embodiments may be replaced, added, and / or subtracted from other described embodiments unless the context indicates otherwise. Therefore, although several embodiments are described above, it will be understood that the present invention is intended to cover all modifications and equivalents within the scope of the appended claims.

Claims

1. A device comprising: A first circuit comprising: a first switch configured to be controlled by a first clock signal, the first switch comprising a first terminal and a second terminal; an amplifier comprising an inverting input, a non-inverting input, and an output, wherein the inverting input is coupled to the second terminal; a first capacitor coupled to the first terminal of the first switch, wherein the first capacitor is formed between a head gimbal assembly and a medium; and a second capacitor comprising a third terminal and a fourth terminal, the third terminal coupled to the inverting input of the amplifier and the fourth terminal coupled to the output of the amplifier, wherein the second capacitor is configured to store charge from the first capacitor during one or more cycles of the first clock signal, Wherein the amplifier is configured to generate an output voltage based at least in part on a change in capacitance of the first capacitor over the one or more cycles of the first clock signal.

2. The apparatus of claim 1, wherein the output voltage indicates a change in height of the head gimbal assembly relative to the media.

3. The apparatus of claim 2, further comprising an analog-to-digital converter configured to convert the output voltage of the amplifier to a digital output, wherein the digital output is associated with a height of the head gimbal assembly.

4. The apparatus of claim 2, further comprising a comparator configured to compare the output voltage to a threshold voltage, wherein the comparator is configured to determine whether a change in the height of the head gimbal assembly exceeds a threshold distance.

5. The apparatus of claim 1, further comprising a second switch coupled in parallel with the second capacitor, the second switch configured to activate after all of the one or more cycles of the first clock signal have elapsed.

6. The apparatus of claim 1, further comprising a second circuit configured to shift a fixed charge from the first capacitor, the second circuit comprising: a third switch including a fifth terminal and a sixth terminal, the fifth terminal being coupled to the inverting input of the amplifier and the sixth terminal being coupled to a third capacitor, the third switch being controlled by the first clock signal, Wherein the third capacitor is configured to remove a fixed amount of charge from the first capacitor in each respective one of the one or more cycles of the first clock signal.

7. The apparatus of claim 6, further comprising a voltage source configured to precharge the third capacitor to an offset voltage between each individual one of the one or more cycles of the first clock signal.

8. A system comprising: Head gimbal assembly; a storage medium, wherein a capacitance is formed between at least a portion of the head gimbal assembly and the storage medium; and Circuit , which is configured to determine the height of the head gimbal assembly relative to the storage medium, the circuit comprising: The first subcircuit comprises: a first switch configured to be controlled by a first clock signal, the first switch comprising a first terminal and a second terminal; an amplifier comprising an inverting input, a non-inverting input, and an output, wherein the inverting input is coupled to the second terminal; a first capacitor coupled to the first terminal of the first switch, wherein the first capacitor is formed by at least a portion of the head gimbal assembly and the storage medium; and a second capacitor comprising a third terminal and a fourth terminal, the third terminal coupled to the inverting input of the amplifier and the fourth terminal coupled to the output of the amplifier, wherein the second capacitor is configured to store charge from the first capacitor during one or more cycles of the first clock signal, Wherein the amplifier is configured to generate an output voltage based at least in part on a change in capacitance of the first capacitor over the one or more cycles of the first clock signal.

9. The system of claim 8, wherein the output voltage indicates a change in height of the head gimbal assembly relative to the storage medium.

10. The system of claim 9, wherein the circuit further comprises an analog-to-digital converter configured to convert the output voltage of the amplifier to a digital output, wherein the digital output is associated with a height of the head gimbal assembly.

11. The system of claim 9, wherein the circuit further comprises a comparator configured to compare the output voltage to a threshold voltage, wherein the comparator is configured to determine whether a change in the height of the head gimbal assembly exceeds a threshold distance.

12. The system of claim 8, further comprising a second switch coupled in parallel with the second capacitor, the second switch configured to activate after all of the one or more cycles of the first clock signal have elapsed.

13. The system of claim 8, further comprising a second subcircuit configured to shift a fixed charge from the first capacitor, the second subcircuit comprising: a third switch including a fifth terminal and a sixth terminal, the fifth terminal being coupled to the inverting input of the amplifier and the sixth terminal being coupled to a third capacitor, the third switch being controlled by the first clock signal, Wherein the third capacitor is configured to remove a fixed amount of charge from the first capacitor in each respective one of the one or more cycles of the first clock signal.

14. The system of claim 13, wherein the second subcircuit further comprises a voltage source configured to precharge the third capacitor to an offset voltage between each individual one of the one or more cycles of the first clock signal.

15. A circuit comprising: a first switch configured to be controlled by a first clock signal, the first switch comprising a first terminal and a second terminal; an amplifier comprising an inverting input, a non-inverting input, and an output, wherein the inverting input is coupled to the second terminal; a first capacitor coupled to the first terminal of the first switch, wherein the first capacitor is formed by at least a portion of a head gimbal assembly and a storage medium; and a second capacitor comprising a third terminal and a fourth terminal, the third terminal coupled to the inverting input of the amplifier and the fourth terminal coupled to the output of the amplifier, wherein the second capacitor is configured to store charge from the first capacitor during one or more cycles of the first clock signal, Wherein the amplifier is configured to generate an output voltage based at least in part on a change in capacitance of the first capacitor over the one or more cycles of the first clock signal.

16. The circuit of claim 15, wherein the output voltage is indicative of a change in height of the head gimbal assembly relative to the media.

17. The circuit of claim 16, wherein the circuit further comprises an analog-to-digital converter configured to convert the output voltage of the amplifier to a digital output, wherein the digital output is associated with a height of the head gimbal assembly.

18. The circuit of claim 16, wherein the circuit further comprises a comparator configured to compare the output voltage to a threshold voltage, wherein the comparator is configured to determine whether a change in the height of the head gimbal assembly exceeds a threshold distance.

19. The circuit of claim 15, further comprising: a third switch including a fifth terminal and a sixth terminal, the fifth terminal being coupled to the inverting input of the amplifier and the sixth terminal being coupled to a third capacitor, the third switch being controlled by the first clock signal, Wherein the third capacitor is configured to remove a fixed amount of charge from the first capacitor in each respective one of the one or more cycles of the first clock signal.

20. The circuit of claim 15, wherein the circuit further comprises a voltage source configured to precharge the third capacitor to an offset voltage between each individual one of the one or more cycles of the first clock signal.

Images