Power architecture for low power modes in storage devices

Description

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Application No. 61/901,905, filed Nov. 8, 2013, entitled “POWER ARCHITECTURE FOR LOW POWER MODES IN STORAGE DEVICES”, which is incorporated herein by reference.

BACKGROUND

Many electronic devices operate in multiple modes of operation, with one of modes usually being a low power mode intended to reduce power consumption. Data storage devices, such as hard disk drives, solid state hybrid drives, and solid state drives, may receive power from a host power supply, which can reside in a desktop or laptop computer or be a standalone power supply, for example. The host may at times indicate to the data storage device that it should go into a low power mode. In many situations, power circuitry inside such an electronic device needs to be able to transition the device into a low power mode that consumes as little power as possible, and quickly transition out of the low power mode if needed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a data storage device with a power control device such as power large scale integrated (PLSI) circuitry according to an embodiment of the invention.

FIG. 2 shows an example power control device that manages transitions to low power modes with switches external to the power control device.

FIG. 3 shows a power control device with an always on domain (AOD) according to an embodiment of the invention.

FIG. 4 is a flow chart showing an example operation of the power control device according to an embodiment of the invention.

FIG. 5 is a flow chart showing another example operation of the power control device according to an embodiment of the invention.

DETAILED DESCRIPTION

Some embodiments of the present disclosure are directed to power control devices for enabling low power mode support through an always on domain (AOD) without the need of load switches external to the power control device. In one embodiment, the power control device is implemented in a data storage device, and can be configured to transition the data storage device into low power modes required for host commands such as DEVSLP, USB Suspend, and SAS Host Suspend, without the need for FET load switches to cut off power to the components inside the data storage device.

While various embodiments are described herein, these embodiments are presented by way of example only, and not intended to limit the scope of protection. Indeed, the novel methods and devices described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions and changes in the form of the methods and devices described herein may be made without departing from the scope of protection. To illustrate some of the embodiments, reference will now be made to the figures.

FIG. 1 shows a data storage device 60 according to an embodiment comprising a head 16 and a disk 18 comprising a plurality of servo tracks 20, wherein each servo track comprises a plurality of servo sectors 22₀-22_N. The data storage device further comprises control circuitry 24 comprising a servo control system operable to actuate the head over the disk in response to the servo sectors 22₀-22_N. The disk is rotated by a spindle motor 46 at a rotational speed that is controlled by the control circuitry 24, for example, a motor driver of the control circuitry 24.

In the embodiment of FIG. 1, the control circuitry 24 processes a read signal 32 emanating from the head 16 to demodulate the servo sectors 22₀-22_N and generate a position error signal (PES) representing an error between the actual position of the head and a target position relative to a target track. A preamplifier (preamp) may be used to improve the read signal 32 from the head 16. In one embodiment, the target track comprises a target data track defined relative to the servo tracks 20, wherein the data tracks may be recorded at the same or different radial density than the servo tracks 20. The control circuitry 24 filters the PES using a suitable compensation filter to generate a control signal 34 applied to a voice coil motor (VCM) 36 which rotates an actuator arm 38 about a pivot in order to actuate the head 16 radially over the disk 18 in a direction that reduces the PES. The control circuitry 24 may also generate a control signal 40 applied to a microactuator 42 in order to actuate the head 16 over the disk 18 in fine movements. Any suitable microactuator 42 may be employed in the embodiments, such as a piezoelectric actuator. In addition, the microactuator 42 may actuate the head 16 over the disk 18 in any suitable manner, such as by actuating a suspension relative to the actuator arm, or actuating a slider relative to the suspension. The servo sectors 22₀-22_N may comprise any suitable head position information, such as a track address for coarse positioning and servo bursts for fine positioning. The servo bursts may comprise any suitable pattern, such as an amplitude based servo pattern or a phase based servo pattern.

The control circuitry 24 may also control solid state memory storage 50, e.g., memory storage comprising solid state NAND memory. For example, where the data storage device 60 is a solid state hybrid drive (SSHD), data may be stored in solid state memory storage 50 in addition to, or instead of, disk 18. In another embodiment, the data storage device 60 is a solid state drive (SSD) that stores data in solid state memory storage 50 instead of magnetic recording media such as disk 18. In an embodiment, the control circuitry 24 may comprise power control device 62, which may include a PLSI (Power Large Scale Integrated) Circuit. The power control device 62, among other things, controls the power consumption of the various components within the data storage device 60.

In one embodiment, the control circuitry 24 may receive commands from a host via host interface. For example, the power control device 62 may respond to a host command by putting components of the data storage device 60 into a lower power mode such as a sleep mode. It should be noted that although FIG. 1 depicts components of magnetic data storage, some embodiments of the invention may be applied to a pure solid state memory-based data storage device without such magnetic data storage components.

FIG. 2 shows an example power control device that manages transitions to low power modes with switches external to the power control device. In order to reduce data storage device power consumption down to single digit mW levels, the example shown in FIG. 2 relies on using low on-resistance FET switches to cut power to virtually the entire electronics of the data storage device. As shown in FIG. 2, host power and host power control (HPC) input are routed through an HPC block 102, which includes control logic 104. The power control device 62 (which includes internal voltage regulators 64, control logic circuitry 66, bias current generators 68, and various internal functional blocks 72) controls the power provided to the various components of the electronic device. In this example, the electronic device is a data storage device with a spindle motor driven by a motor driver 70. The power control device 62 also controls various voltage regulators 74 external to the power control device.

However, as shown in FIG. 2, the power control device 62 is isolated from the HPC block 102, which is responsible for shutting off power (through the FET switches shown) when the data storage device needs to go into low power state in response to a command from the host. In order to achieve the very low power consumption requirements of modes such as DEVSLP, USB Suspend, and SAS Host Suspend, these FET switches must be sufficiently large and possess very low RDS-ON (Resistance Drain to Source in ON state of a FET transistor), in order to minimize the voltage drop across the FET when in the ON-state. Apart from the FET switches, alternative solutions to enable the low power state include the so called ‘e-fuse’ components and discrete FETs with appropriate gate drivers and control logic. However, these low power state enablers are discrete components external to the power control device, and thus carry a significant cost burden.

FIG. 3 shows a power control device with an always on domain (AOD) according to an embodiment of the invention. Unlike the example in FIG. 2, where the host power control is disintegrated or separated from the power control device, the power control device 62 includes an always-on-domain (AOD)/host power control (HPC) 124. The AOD 124 includes, in one embodiment, control logic circuitry 126 for controlling power from a power source (e.g., host power input 122) and internal voltage regulators 128 coupled to the power source. The output of the voltage regulators 128 are fed to bias current generators 130 and load switches 132. In addition, the AOD 124 also includes a clock control 134 controlled by the control logic circuitry 126.

In one embodiment, the power control device 62 includes, outside of the AOD, various functional blocks 142, which generically represent some functional portions of the power control device 62. Some functional blocks 142 are specifically illustrated. For example, FIG. 3 shows a motor driver 138, and voltage regulators 144 configured to regulate voltage from one or more external power sources (e.g., the host). As shown, these components outside of the AOD are powered from internally generated voltage supplies and bias current generators within the AOD.

In contrast to the configuration shown in FIG. 2, the internal voltage regulators 128, the bias current generators 130, the load switches 132, and the clock control 134 are all within the AOD 124, where the control logic circuitry 126 is responsible for power routing and proper control that are necessary to achieve a low or ultra low power state. Such an arrangement enables the low power state support without needing to use aforementioned solutions such as external FET switches.

In one embodiment, the transition to, and out of, a low power state works as shown in the flow diagram of FIG. 4 depicting a process 200. At block 202, the control logic circuitry 126 is configured to receive a signal to go into a lower power state. The signal may be a command from the host power control input 120 (e.g., DEVSLP, Host Suspend, etc.). The various power state commands and the handling of those commands in a power control device are additionally described in co-pending application Ser. No. 14/146,555, filed Jan. 2, 2014, entitled “POWER CONTROL MODULE FOR DATA STORAGE DEVICE” to Ferris et al., which is hereby incorporated by reference. In response to the signal, at block 204, the control logic circuitry may initiate a shut-down sequence of the load switches 132 and the bias current generators 130 within the AOD in a controlled manner, which disables circuitry outside of the AOD. This includes (1) the functional blocks 142 of the power control device and (2) other external loads controlled by the power control device (e.g., DRAM, drive controller (SoC), solid state memory (e.g., NAND) in a data storage device). Additionally, the shut-down sequence may include sequencing off voltage regulators 144 external to the AOD and the clock control 134 within the AOD. If the power control device 62 is in a data storage device with a rotating magnetic recording sub-system, the control logic circuitry 126 may additionally shut power off to the motor driver 138. At block 206, the control logic circuitry 126 may operate in a low power state to detect a wake-up signal to transition out of the low power state. At block 208, a wake-up signal is detected, in response to which the control logic circuitry 126 is configured to initiate a start-up sequence of the components within the AOD to enable circuitry outside of the AOD (block 210).

The AOD/HPC configuration allows for a system level design that can achieve a very low power goal. In an embodiment within a data storage device with a rotating magnetic recording sub-system, except for the preamp supply (e.g., +5V), all data storage device power consumption, passes through, or is controlled by, the power control device. This means that, in one embodiment, reducing the data storage device power consumption can be achieved by means of an appropriate control logic in the AOD of the power control device, along with putting the preamp into a lower power/sleep mode (e.g., with firmware) to take care of the one power domain not under control of the power control device. The power saving that can be achieved can be significant in some embodiments. Once the shut-down sequence is complete, the power draw could be, for example, in the range of hundreds of uA.

In one embodiment, the control logic circuitry 126 may be configured to communicate the status of the HPC, via HPC_Out, to a controller of the data storage device (not shown). In addition, in one embodiment, the AOD 124 may include a serial interface 150 through which firmware executing from an external controller could invoke a transition to a low power mode (e.g., an Ultra Low Power (ULP) mode). For example, the firmware could cause the VCM to be retracted and spindle motor to be spun-down (as part of going into a Sleep mode) and then invoke the ULP mode in the control logic circuitry 126 through the serial interface 150.

In one embodiment, upon receiving the signal from the host indicating a first type of transition (e.g., DEVSLP) to a lower power state, the control logic circuitry 126 is configured to send a signal to the controller of the data storage device to cause the controller to initiate one or more operations to prepare the data storage device to enter into the low power state (e.g., finish last writes, spin down disk, park head, etc.). The control logic circuitry 126 then awaits an input signal from the controller that the operations are complete, and then initiates the shut-down sequence after receiving the input signal from the data storage device's controller.

In another embodiment, upon receiving the signal from the host indicating a second type of transition to a lower power state (e.g., Host Suspend), the control logic circuitry 126 is configured to initiate the shut-down sequence without waiting for the input signal from the data storage device's controller.

In one embodiment, upon receiving a wake signal from the host (e.g., received via input 120), the AOD 124 is configured in one embodiment to reverse the sequence as follows:

a) Turn on internal voltage and current sources to enable circuitry outside of the AOD;

b) Sequence all regulators on in a controlled manner;

c) A ULP status bit is read (e.g., by firmware) to determine if it is a cold boot or coming out of ULP mode; and

d) A state is changed (e.g., by firmware) from ULP mode to Sleep to Ready modes.

In one embodiment, there are additional architectural changes from a device physics standpoint that may be implemented. To achieve low current within the power device for deep sleep modes and eliminate latch up through SCR (Silicon-Controlled Rectifier) action for load switches in high current paths, a deep trench isolation process technology may be utilized in one embodiment. The deep trench isolation technologies typically increase the packing density of devices, by bringing them closer together to minimize die size increases. Isolation spacing within the deep trench should follow minimum design requirements to prevent internal transistor cross conduction mechanisms. Deep trench isolation also reduces the effects of inter-well latch up and SCR parasitics. The mixed signal device will have a significant reduction in junction capacitance, reducing parasitics. Deep trench isolation will also reduce effects of fly back currents and voltages seen in data storage technology from motors or recirculating currents as the devices enter or awake from these modes.

FIG. 5 is a flow chart showing another example process 230 of the power control device according to an embodiment of the invention. At block 232, the control logic circuitry 126 detects whether the host power control input has been asserted. If so (Y branch), at block 234 it sets the host power control status, which allows for firmware in the data storage device controller to detect that the host power control input has been asserted. In that way, the firmware can perform housekeeping operations to ready the data storage device for the transition to the low power state. Once the housekeeping operations are completed, the firmware may indicate through the controller power input readiness for the next stage of the low power state transition. Therefore, at block 236, the controller power control input is checked to see if it has been set. If so, the shut-down sequence is initiated, which in one embodiment includes sequencing off the regulators (block 238), the clocks (block 240), the internal loads (block 242) and the internal bias currents (block 244). After which the circuitry outside of the AOD is disabled and a low power state is achieved.

At block 246, the control logic circuitry 126 detects whether the host power control input has been de-asserted. As long as it has not been de-asserted (N branch), the low power state persists. However, if it has been de-asserted (Y branch), the control logic circuitry 126 initiates the start-up sequence to wake from the low power state, which in one embodiment includes sequencing on the internal bias currents (block 248), the internal loads (block 250), the clocks (block 252), and the regulators (block 254). This completes the transition out of the low power state and the flow returns to the top.

Going back to block 232, on the N branch, the control logic circuitry 126 checks whether the controller power control input has been set (block 260). If so, a similar shut-down sequence is followed in one embodiment to sequence off the regulators (block 262), the clocks (block 264), the internal loads (block 266) and the internal bias currents (block 268). The device is now in a low power state. When the controller power control input is reset at block 270, the control logic circuitry 126 in one embodiment initiates the start-up sequence to wake from the low power state, which in one embodiment includes sequencing on the internal bias currents (block 272), the internal loads (block 274), the clocks (block 276), and the regulators (block 278). This completes the transition out of the low power state and the flow returns to the top.

Any suitable control circuitry may be employed to implement the flow diagrams in the above embodiments, such as any suitable integrated circuit or circuits. For example, the control circuitry may be implemented within a read channel integrated circuit, or in a component separate from the read channel, such as a disk controller, or certain operations described above may be performed by a read channel and others by a disk controller. In one embodiment, the read channel and disk controller are implemented as separate integrated circuits, and in an alternative embodiment they are fabricated into a single integrated circuit or system on a chip (SOC). In addition, the control circuitry may include a suitable preamp circuit implemented as a separate integrated circuit, integrated into the read channel or disk controller circuit, or integrated into a SOC.

In one embodiment, the control circuitry comprises a microprocessor executing instructions, the instructions being operable to cause the microprocessor to perform the flow diagrams described herein. The instructions may be stored in any computer-readable medium. In one embodiment, they may be stored on a non-volatile semiconductor memory external to the microprocessor, or integrated with the microprocessor in a SOC. In another embodiment, the instructions are stored on the disk and read into a volatile semiconductor memory when the data storage device is powered on. In yet another embodiment, the control circuitry comprises suitable logic circuitry, such as state machine circuitry. Also, the various components described may be implemented as software and/or firmware on a processor, ASIC/FPGA, or dedicated hardware. As an additional example, some of the above described power module embodiments may be implemented in electronic devices other than data storage devices.

The various features and processes described above may be used independently of one another, or may be combined in various ways. All possible combinations and subcombinations are intended to fall within the scope of this disclosure. In addition, certain method, event or process blocks may be omitted in some implementations. The methods and processes described herein are also not limited to any particular sequence, and the blocks or states relating thereto can be performed in other sequences that are appropriate. For example, described tasks or events may be performed in an order other than that specifically disclosed, or multiple may be combined in a single block or state. The example tasks or events may be performed in serial, in parallel, or in some other manner. Tasks or events may be added to or removed from the disclosed example embodiments. The example systems and components described herein may be configured differently than described. For example, elements may be added to, removed from, or rearranged compared to the disclosed example embodiments.

While certain example embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions disclosed herein. Thus, nothing in the foregoing description is intended to imply that any particular feature, characteristic, step, module, or block is necessary or indispensable. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the embodiments disclosed herein.

Also, the features and attributes of the specific embodiments disclosed above may be combined in different ways to form additional embodiments, all of which fall within the scope of the present disclosure. Although the present disclosure provides certain preferred embodiments and applications, other embodiments that are apparent to those of ordinary skill in the art, including embodiments which do not provide all of the features and advantages set forth herein, are also within the scope of this disclosure. Accordingly, the scope of protection is defined only by the claims.