Patent Publication Number: US-2023145999-A1

Title: Sequencer chaining circuitry

Description:
PRIORITY INFORMATION 
     This application is a Continuation of U.S. application Ser. No. 16/816,615 filed on Mar. 12, 2020 which claims priority to U.S. Provisional Application Ser. No. 62/954,812, filed on Dec. 30, 2019, the contents of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     Embodiments of the disclosure relate generally to memory sub-systems, and more specifically, relate to chaining circuitry for sequencers. 
     BACKGROUND 
     A memory sub-system can include one or more memory devices that store data. The memory devices can be, for example, non-volatile memory devices and volatile memory devices. In general, a host system can utilize a memory sub-system to store data at the memory devices and to retrieve data from the memory devices. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure will be understood more fully from the detailed description given below and from the accompanying drawings of various embodiments of the disclosure. 
         FIG.  1    illustrates an example computing system that includes a memory sub-system in accordance with some embodiments of the present disclosure. 
         FIG.  2    illustrates an example of sequencer chaining circuitry in accordance with some embodiments of the present disclosure. 
         FIG.  3    illustrates an example of sequencer chaining circuitry in accordance with some embodiments of the present disclosure. 
         FIG.  4    is a flow diagram of an example method for operating sequencer chaining circuitry in accordance with some embodiments of the present disclosure. 
         FIG.  5    is a block diagram of an example computer system in which embodiments of the present disclosure may operate. 
     
    
    
     DETAILED DESCRIPTION 
     Aspects of the present disclosure are directed to memory sub-systems that include sequencer chaining circuitry. A memory sub-system can be a storage device, a memory module, or a hybrid of a storage device and memory module. Examples of storage devices and memory modules are described below in conjunction with  FIG.  1   . In general, a host system can utilize a memory sub-system that includes one or more memory components, such as memory devices that store data. The host system can provide data to be stored at the memory sub-system and can request data to be retrieved from the memory sub-system. 
     A sequencer is a device that can be used to control an order in which events occur in an electronic system. As one example, a sequencer can be used for power sequencing within a memory sub-system such as a dual in-line memory module (DIMM), non-volatile dual in-line memory module (NVDIMM), solid state drive (SSD), etc. For example, a memory sub-system can include various components (e.g., integrated circuits) requiring different power supply voltages (e.g., rail voltages) which often need to be supplied in a particular order and/or for a particular duration in order to comply with system specifications (e.g., to prevent lock-up during power-up and/or power-down). Example components often requiring sequencing can include core logic such as a microprocessor, input/output (I/O) circuitry, and various auxiliary circuits such as phase-locked loops among various other circuitry that can require different supply rails. 
     Conventional sequencers have a limited quantity of output channels, which might be 3, 4, 5, or 6. Various electronic systems can require sequencing of more outputs than are provided by a particular sequencer. Employing multiple separate sequencers to provide a required quantity of output channels can be problematic since there is not a direct way to sequence continuously from one sequencer to the next while maintaining strict timing requirements such as may be needed for power sequencing, for example. 
     Aspects of the present disclosure address the above and other deficiencies by providing sequencer chaining circuitry that can be scaled to support sequencer output requirements of various systems. Embodiments of the present disclosure employ chaining circuitry used to connect separate sequencers (e.g., separate integrated circuits) in a feed-forward and/or feed-backward manner to ensure proper timing during sequencing in both a forward and reverse order. Although various examples herein refer to power supply sequencing, embodiments are not so limited. That is, sequencer chaining circuitry described herein can be used in various other contexts associated with an electronic system, such as command selection, command processing, etc. 
       FIG.  1    illustrates an example computing system  100  that includes a memory sub-system  110  in accordance with some embodiments of the present disclosure. The memory sub-system  110  can include media, such as one or more volatile memory devices (e.g., memory device  140 ), one or more non-volatile memory devices (e.g., memory device  130 ), or a combination of such. 
     A memory sub-system  110  can be a storage device, a memory module, or a hybrid of a storage device and memory module. Examples of a storage device include a solid-state drive (SSD), a flash drive, a universal serial bus (USB) flash drive, an embedded Multi-Media Controller (eMMC) drive, a Universal Flash Storage (UFS) drive, a secure digital (SD) card, and a hard disk drive (HDD). Examples of memory modules include a dual in-line memory module (DIMM), a small outline DIMM (SO-DIMM), and various types of non-volatile dual in-line memory modules (NVDIMMs). 
     The computing system  100  can be a desktop computer, laptop computer, network server, mobile device, a vehicle (e.g., automobile, airplane, drone, train, or other conveyance), Internet of Things (IoT) enabled device, embedded computer (e.g., one included in a vehicle, industrial equipment, or a networked commercial device), or such computing device that includes memory and a processing device (e.g., a processor). 
     The computing system  100  can include a host system  120  that is coupled to one or more memory sub-systems  110 . In some embodiments, the host system  120  is coupled to different types of memory sub-systems  110 .  FIG.  1    illustrates an example of a host system  120  coupled to one memory sub-system  110 . As used herein, “coupled to” or “coupled with” generally refers to a connection between components, which can be an indirect communicative connection or direct communicative connection (e.g., without intervening components), whether wired or wireless, including connections such as electrical, optical, magnetic, etc. 
     The host system  120  can include a processor chipset and a software stack executed by the processor chipset. The processor chipset can include one or more cores, one or more caches, a memory controller (e.g., NVDIMM controller), and a storage protocol controller (e.g., PCIe controller, SATA controller). The host system  120  uses the memory sub-system  110 , for example, to write data to the memory sub-system  110  and read data from the memory sub-system  110 . 
     The host system  120  can be coupled to the memory sub-system  110  via a physical host interface. Examples of a physical host interface include, but are not limited to, a serial advanced technology attachment (SATA) interface, a peripheral component interconnect express (PCIe) interface, universal serial bus (USB) interface, Fibre Channel, Serial Attached SCSI (SAS), Small Computer System Interface (SCSI), a double data rate (DDR) memory bus, a dual in-line memory module (DIMM) interface (e.g., DIMM socket interface that supports Double Data Rate (DDR)), Open NAND Flash Interface (ONFI), Double Data Rate (DDR), Low Power Double Data Rate (LPDDR), or any other interface. The physical host interface can be used to transmit data between the host system  120  and the memory sub-system  110 . The host system  120  can further utilize an NVM Express (NVMe) interface to access components (e.g., memory devices  130 ) when the memory sub-system  110  is coupled with the host system  120  by the PCIe interface. The physical host interface can provide an interface for passing control, address, data, and other signals between the memory sub-system  110  and the host system  120 .  FIG.  1    illustrates a memory sub-system  110  as an example. In general, the host system  120  can access multiple memory sub-systems via a same communication connection, multiple separate communication connections, and/or a combination of communication connections. 
     The memory devices  130 , 140  can include any combination of the different types of non-volatile memory devices and/or volatile memory devices. The volatile memory devices (e.g., memory device  140 ) can be, but are not limited to, random access memory (RAM), such as dynamic random access memory (DRAM) and synchronous dynamic random access memory (SDRAM). 
     Some examples of non-volatile memory devices (e.g., memory device  130 ) include not-AND (NAND) type flash memory and write-in-place memory, such as a three-dimensional cross-point (“3D cross-point”) memory device, which is a cross-point array of non-volatile memory cells. A cross-point array of non-volatile memory can perform bit storage based on a change of bulk resistance, in conjunction with a stackable cross-gridded data access array. Additionally, in contrast to many flash-based memories, cross-point non-volatile memory can perform a write in-place operation, where a non-volatile memory cell can be programmed without the non-volatile memory cell being previously erased. NAND type flash memory includes, for example, two-dimensional NAND (2D NAND) and three-dimensional NAND (3D NAND). 
     Each of the memory devices  130  can include one or more arrays of memory cells. One type of memory cell, for example, single level cells (SLC) can store one bit per cell. Other types of memory cells, such as multi-level cells (MLCs), triple level cells (TLCs), quad-level cells (QLCs), and penta-level cells (PLCs) can store multiple bits per cell. In some embodiments, each of the memory devices  130  can include one or more arrays of memory cells such as SLCs, MLCs, TLCs, QLCs, PLCs, or any combination of such. In some embodiments, a particular memory device can include an SLC portion, and an MLC portion, a TLC portion, a QLC portion, or a PLC portion of memory cells. The memory cells of the memory devices  130  can be grouped as pages that can refer to a logical unit of the memory device used to store data. With some types of memory (e.g., NAND), pages can be grouped to form blocks. 
     Although non-volatile memory devices such as 3D cross-point array of non-volatile memory cells and NAND type memory (e.g., 2D NAND, 3D NAND) are described, the memory device  130  can be based on any other type of non-volatile memory, such as read-only memory (ROM), phase change memory (PCM), self-selecting memory, other chalcogenide based memories, ferroelectric transistor random-access memory (FeTRAM), ferroelectric random access memory (FeRAM), magneto random access memory (MRAM), Spin Transfer Torque (STT)-MRAM, conductive bridging RAM (CBRAM), resistive random access memory (RRAIVI), oxide based RRAIVI (OxRAM), not-OR (NOR) flash memory, and electrically erasable programmable read-only memory (EEPROM). 
     A memory sub-system controller  115  (or controller  115  for simplicity) can communicate with the memory devices  130  and/or  140  to perform operations such as reading data, writing data, or erasing data at the memory devices  130  and/or  140  and other such operations. The memory sub-system controller  115  can include hardware such as one or more integrated circuits and/or discrete components, a buffer memory, or a combination thereof. The hardware can include a digital circuitry with dedicated (i.e., hard-coded) logic to perform the operations described herein. The memory sub-system controller  115  can be a microcontroller, special purpose logic circuitry (e.g., a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), etc.), or other suitable processor. 
     The memory sub-system controller  115  can include processing device such as a processor  117  configured to execute instructions stored in a local memory  119 . In the illustrated example, the local memory  119  of the memory sub-system controller  115  includes an embedded memory configured to store instructions for performing various processes, operations, logic flows, and routines that control operation of the memory sub-system  110 , including handling communications between the memory sub-system  110  and the host system  120 . 
     In some embodiments, the local memory  119  can include memory registers storing memory pointers, fetched data, etc. The local memory  119  can also include read-only memory (ROM) for storing micro-code, for example. While the example memory sub-system  110  in  FIG.  1    has been illustrated as including the memory sub-system controller  115 , in another embodiment of the present disclosure, a memory sub-system  110  does not include a memory sub-system controller  115 , and can instead rely upon external control (e.g., provided by an external host, or by a processor or controller separate from the memory sub-system). 
     In general, the memory sub-system controller  115  can receive commands or operations from the host system  120  and can convert the commands or operations into instructions or appropriate commands to achieve the desired access to the memory devices  130 . The memory sub-system controller  115  can be responsible for other operations such as wear leveling operations, garbage collection operations, error detection and error-correcting code (ECC) operations, encryption operations, caching operations, and address translations between a logical address (e.g., logical block address (LBA), namespace) and a physical address (e.g., physical block address) that are associated with the memory devices  130 . The memory sub-system controller  115  can further include host interface circuitry to communicate with the host system  120  via the physical host interface. The host interface circuitry can convert the commands received from the host system into command instructions to access the memory devices  130  and/or  140  as well as convert responses associated with the memory devices  130 / 140  into information for the host system  120 . 
     The memory sub-system  110  can also include additional circuitry or components that are not illustrated. In some embodiments, the memory sub-system  110  can include a cache or buffer (e.g., DRAM) and address circuitry (e.g., a row decoder and a column decoder) that can receive an address from the memory sub-system controller  115  and decode the address to access the memory devices  130 . 
     In some embodiments, the memory devices  130 / 140  include a local media controller  135  that operates in conjunction with memory sub-system controller  115  to execute operations on one or more memory cells of the memory devices  130 / 140 . An external controller (e.g., memory sub-system controller  115 ) can externally manage the memory devices  130 / 140  (e.g., perform media management operations on the memory devices). In some embodiments, a memory device  130  is a managed memory device, which is a raw memory device combined with a local controller (e.g., local controller  135 ) for media management within the same memory device package. An example of a managed memory device is a managed NAND (MNAND) device. 
     The memory sub-system controller  115  can also include power sequencer chaining circuitry  152  coupled to a number of sequencers  153 , which can serve as a sequencing network in accordance with various embodiments of the present disclosure (e.g., the sequencing networks described below in association with  FIG.  2    and  FIG.  3   ). As described in association with  FIG.  2    and  FIG.  3   , the sequencer chaining circuitry  152  (e.g.,  252  in  FIG.  0 . 2   ) can include a number of logic gates (e.g., AND gates and OR gates) and can be configured to assert respective sequencer enable signals provided to the chained sequencers  153  in accordance with a first sequence responsive to assertion of a primary enable signal. The chaining circuitry  152  can also be configured to assert the respective sequencer enable signals provided to the plurality of chained sequencers  153  in accordance with a second sequence responsive to deassertion of the primary enable signal. Although the sequencer chaining circuitry  152  and sequencers  153  are shown as part of controller  115 , embodiments are not so limited. For example, the circuitry  152  and/or  153  may be implemented external to the controller  115 , such as on the host  120  or elsewhere in the memory sub-system  110  (e.g., independently or as part of a power management integrated circuit). 
       FIG.  2    illustrates an example of a chained sequencer network in accordance with a number of embodiments of the present disclosure. In this example, the chained network includes three sequencers  253 - 1  (SEQUENCER i−1),  253 - 2  (SEQUENCER i), and  253 - 3  (SEQUENCER i+1) coupled to the sequencer chaining circuitry  252  and referred to collectively as sequencers  253 . The sequencer chaining circuitry  252  is analogous to sequencer chaining circuitry  152  in  FIG.  1   . Each of the sequencers  253  comprises “m” outputs (e.g., channels) provided to respective components. In this example, the outputs of sequencer  253 - 1  are provided to respective ones of components  254 - 1  (shown as SEQi−1_1, SEQi−1_2, SEQi−1_ m ), the outputs of sequencer  253 - 2  are provided to respective ones of components  254 - 2  (shown as SEQi_1, SEQi_2, . . . , SEQi_m), and the outputs of sequencer  253 - 3  are provided to respective ones of components  254 - 3  (shown as SEQi+1_1, SEQi+1_2, . . . , SEQi+1_m). The components  254 - 1 ,  254 - 2 , and  254 - 3  can be, for example, voltage regulators configured to provide power rails to a power sequence dependent device such as a memory device. Accordingly, the output signals of the sequencers  253  can be enable signals, for example. 
     The sequencers  253  can be separate sequencers (e.g., separate integrated circuits). The sequencers  253 - 1 ,  253 - 2 , and  253 - 3  are enabled and disabled via respective sequencer enable signals SEQi−1_EN, SEQi_EN, and seQi+1_EN provided via the chaining circuitry  252 . When enabled, the sequencers  253  are configured to provide their respective output signals in a particular order (e.g., from  1  to m). The sequencers  253  can be configured to provide their respective output signals in a reverse order (e.g., m to 1) responsive to being disabled (e.g., via deassertion of their respective sequencer enable signals). As described herein, the chaining circuitry  252  is configured to provide the sequencer enable signals SEQi−1_EN, SEQi_EN, and seQi+1_EN to the respective sequencers  253 - 1 ,  253 - 2 , and  253 - 3  according to a first sequence responsive to assertion of a primary enable signal  251  provided thereto and according to a second sequence responsive to deassertion of the primary enable signal  251 . As an example, the primary enable signal  251  can be asserted (e.g., via a host system such as  120  or a processing device  117 ) in association with powering up a memory sub-system such as an NVDIMM and can be deasserted in association with powering down the memory sub-system. Therefore, it can be beneficial to enable/disable the sequencers  253  in a particular order to avoid adverse effects such as violating power-up/down sequence requirements. In a number of embodiments, the order in which the sequencers  253  are disabled (e.g., during device power-down) is a reverse order of that in which the sequencers are enabled (e.g., during device power-up). 
     As shown in  FIG.  2   , the chaining circuitry  252  comprises a number of AND gates  255 - 1 ,  255 - 2 , and  255 - 3  (referred to collectively as gates  255 ) and a number of OR gates  256 - 1 ,  256 - 2 , and  256 - 3  (referred to collectively as gates  256 ). In this example, each of the sequencers  253  have an AND gate  255  and an OR gate  256  corresponding thereto. The primary enable signal  251  is provided to each of the OR gates  256 . In this example, an output of each of the OR gates  255  is provided as an input to a corresponding AND gate  255 . The outputs of the AND gates  255  provide the sequencer enable signals SEQi−1_EN, SEQi_EN, and seQi+1_EN to the sequencers  253 . 
     As shown in  FIG.  2   , particular ones of the sequencer output signals are provided (e.g., fed back) to logic gates  255 / 256  corresponding to next and/or prior sequencers  253  in the chained configuration to facilitate enabling the sequencers  253  in a particular order. For instance, sequencer output signal  257 - 1  of sequencer  253 - 1  is provided as an input to AND gate  255 - 2  corresponding to sequencer  253 - 2 . Similarly, sequencer output signal  257 - 2  of sequencer  253 - 2  is provided as an input to AND gate  255 - 3  corresponding to sequencer  253 - 3 . Also, sequencer output signal  258 - 1  of sequencer  253 - 2  is provided as an input to OR gate  256 - 1  corresponding to sequencer  253 - 1 , and sequencer output signal  258 - 2  of sequencer  253 - 3  is provided as an input to OR gate  256 - 2  corresponding to sequencer  253 - 2 . In this manner, responsive to assertion of the primary enable signal  251 , sequencer  253 - 2  will not be enabled (via enable signal SEQi_EN) until sequencer output signal  257 - 1  is asserted, and sequencer  253 - 3  will not be enabled (via enable signal SEQi+1_EN) until sequencer output signal  257 - 2  is asserted. In a similar manner, responsive to deassertion of the primary enable signal  251 , sequencer  253 - 2  will not be disabled until sequencer output signal  258 - 2  is deasserted, and sequencer  253 - 1  will not be disabled until sequencer output signal  258 - 1  is deasserted 
     In operation, responsive to an assertion of the primary enable signal  251 , the sequencers  253  are enabled in order with sequencer  253 - 1  being enabled first, followed by sequencer  253 - 2  and then sequencer  253 - 3 . That is, initially sequencer  253 - 1  is enabled via assertion of the output of AND gate  255 - 1  (via assertion of the output of OR gate  256 - 1 ) due to assertion of primary enable signal  251 . Sequencers  253 - 2  and  253 - 2  are disabled initially since one of the inputs of their respective corresponding AND gates  255 - 2  and  255 - 3  are deasserted. Once sequencer output  257 - 1  is asserted, both inputs to AND gate  255 - 2  are asserted and its output (SEQi_EN) is asserted to enable sequencer  253 - 2  (while sequencer  253 - 3  remains disabled). Once sequencer output  257 - 2  is asserted, both inputs to AND gate  255 - 3  are asserted and its output (SEQi+1_EN) is asserted to enable sequencer  253 - 3 . It is noted that sequencer output signals  258 - 1  and  258 - 2  remain asserted in order to maintain the prior sequencers  253  in the chain in an enabled state responsive to deassertion of the primary enable signal  251  (e.g., during power-down). 
     Responsive to the a subsequent deassertion of primary enable signal  251 , the configuration of the chaining circuitry  252  allows the sequencers  253  to operate in the reverse sequence (e.g., sequencer  253 - 3  being disabled prior to disabling of sequencer  253 - 2 , and sequencer  253 - 2  being disabled prior to disabling of sequencer  253 - 1 ). For instance, responsive to deassertion of enable signal  251 , sequencer  253 - 3  will be disabled first as the output of OR gate  256 - 3  deasserts such that the output of AND gate  255 - 3  deasserts. In contrast, sequencer  253 - 2  initially remains enabled responsive to the deassertion of enable signal  251  because both of the inputs (sequencer output signal  257 - 1  and sequencer output signal  258 - 2 ) to corresponding AND gate  255 - 2  remain asserted (e.g., logic high). Once signal  258 - 2  is deasserted by sequencer  253 - 1 , the output of OR gate  256 - 2  deasserts, which then causes deassertion of the sequencer enable signal SEQi_EN being output from AND gate  255 - 2 . Similarly, once sequencer output signal  258 - 1  is deasserted by sequencer  253 - 2 , the output of OR gate  256 - 1  deasserts causing deassertion of the sequencer enable signal SEQi−1_EN being output from AND gate  255 - 1 . 
       FIG.  3    illustrates an example of a chained sequencer network in accordance with a number of embodiments of the present disclosure. In this example, the chained network includes sequencers  353 - 1  (SEQUENCER 1),  353 - 2  (SEQUENCER 2),  353 - 3  (SEQUENCER 3), . . . ,  353 -N(SEQUENCER n) coupled to the sequencer chaining circuitry  352  and referred to collectively as sequencers  353 . The sequencer chaining circuitry  352  is analogous to sequencer chaining circuitry  152  in  FIG.  1   . Each of the sequencers  353  comprises “m” outputs (e.g., channels) provided to respective components. In this example, the outputs of sequencer  353 - 1  are provided to respective ones of components  354 - 1  (shown as SEQ1_1, SEQ1_2, . . . , SEQ1_m), the outputs of sequencer  353 - 2  are provided to respective ones of components  354 - 2  (shown as SEQ2_1, SEQ2_2, . . . , SEQ2_m), the outputs of sequencer  353 - 3  are provided to respective ones of components  354 - 3  (shown as SEQ3_1, SEQ3_2, . . . , SEQ3_m) and the outputs of sequencer  353 -N are provided to respective ones of components  354 -N (shown as SEQn_1, SEQn_2, . . . , SEQn_m). The components  354 - 1 ,  354 - 2 ,  354 - 3 , . . . ,  354 -N can be, for example, voltage regulators configured to provide power rails to a power sequence dependent device such as a memory device. Accordingly, the output signals of the sequencers  353  can be enable signals, for example. 
     The chaining circuitry  352  is configured to control enabling and disabling of the sequencers  353  via assertion and deassertion of respective sequencer enable signals SEQ1_EN, SEQ2_EN, SEQ3_EN, . . . , SEQn_EN. The sequencers  353  are coupled in a chained configuration via feedback of sequencer output signals (e.g.,  357 - 1 ,  357 - 2 ,  357 - 3 ,  358 - 1 ,  358 - 2 , and  358 - 3 ) to the chaining circuitry  352  such that the sequencer outputs are asserted in a particular order (e.g., forward and reverse). 
     The example shown in  FIG.  3    is similar to the example shown in  FIG.  2   . For example, the chaining circuitry  352  includes a number of OR gates  356 - 1 ,  356 - 2 ,  356 - 3  and a number of AND gates  355 - 1 ,  355 - 2 , and  355 -N−1. However, in the example shown in  FIG.  3   , the first sequencer  353 - 1  in the chain includes a single OR gate  356 - 1  corresponding thereto, and the last sequencer  353 -N in the chain includes a single AND gate  355 -N−1 corresponding thereto. Each of the other sequencers  353  have an OR gate  356  and an AND gate  355  corresponding thereto. The reduction of logic gates  355 / 356  per sequencer of circuitry  352  as compared to circuitry  252  is due to removal of the AND gate (e.g.,  255 - 1 ) corresponding to the first sequencer in the chain and removal of the OR gate (e.g.,  256 - 3 ) corresponding to the last sequencer in the chain because those gates become redundant as single input gates. 
     As shown in  FIG.  3    and as described above in association with  FIG.  2   , particular outputs of the sequencers  353  are provided to particular logic gates  355 / 356  corresponding to next and/or prior sequencers  353  in the chained configuration to facilitate enabling the sequencer outputs in a particular order (e.g., due to assertion of the primary enable signal  351 ) or reverse order (e.g., due to deassertion of signal  351 ). For example, the output signal  357 - 1  provided to component “SEQ1_m” from sequencer  353 - 1  is also provided to an input of the AND gate  355 - 1  corresponding to sequencer  353 - 2 , the output signal  357 - 2  provided to component “SEQ2_m” from sequencer  353 - 2  is also provided to an input of the AND gate  355 - 2  corresponding to sequencer  353 - 3 , and the output signal  357 - 3  provided to component “SEQ3 m” from sequencer  353 - 3  is also provided to an input of the AND gate  355 -N−1 corresponding to sequencer  353 -N. Similarly, the output signal  358 - 3  provided to component “SEQn_1” from sequencer  353 -N is also provided to an input of the OR gate  356 - 3  corresponding to sequencer  353 - 3 , the output signal  358 - 2  provided to component “SEQ3_1” from sequencer  353 - 3  is also provided to an input of the OR gate  356 - 2  corresponding to sequencer  353 - 2 , and the output signal  357 - 1  provided to component “SEQ2_1” from sequencer  353 - 2  is also provided to an input of the OR gate  356 - 1  corresponding to sequencer  353 - 1 . 
     In operation, the configuration of the sequencer chaining circuitry  352  and sequencers  353  provides for sequencing output signals in order from the first sequencer  353 - 1  to the last sequencer  353 -N responsive to assertion of the primary enable signal  351 . Additionally, the configuration of the circuitry  352  provides for sequencing output signals in reverse order from the last sequencer  353 -N to the first sequencer  353 - 1  responsive to deassertion of the primary enable signal  351 . In embodiments in which the components  354  are voltage regulators such as described in association with  FIG.  2   , the circuitry can be used to provide sequenced power rails to a power sequence dependent device. That is, the sequenced power signals can be provided in a first order during power-up of the device and in a reverse order during power-down (e.g., due to a transient low power event or otherwise). 
       FIG.  4    is a flow diagram of an example method  403  for operating sequencer chaining circuitry in accordance with some embodiments of the present disclosure. The method  403  can be performed by processing logic that can include hardware (e.g., processing device, circuitry, dedicated logic, programmable logic, microcode, hardware of a device, integrated circuit, etc.), software (e.g., instructions run or executed on a processing device), or a combination thereof. In some embodiments, the method  403  is performed by the sequencer chaining circuitry  262  of  FIG.  2  or  362    of  FIG.  3   . Although shown in a particular sequence or order, unless otherwise specified, the order of the processes can be modified. Thus, the illustrated embodiments should be understood only as examples, and the illustrated processes can be performed in a different order, and some processes can be performed in parallel. Additionally, one or more processes can be omitted in various embodiments. Thus, not all processes are required in every embodiment. Other process flows are possible. 
     At operation  442 , a primary enable signal provided to chaining circuitry coupled to a plurality of sequencers is asserted. The primary enable signal can be asserted via a processing resource and can be asserted in association with powering up a memory sub-system, for example. 
     At operation  444 , responsive to assertion of the primary enable signal, respective sequencer enable signals provided to the plurality of sequencers can be asserted via the chaining circuitry and in accordance with a first sequence. 
     At operation  446 , responsive to deassertion of the primary enable signal, the respective sequencer enable signals provided to the plurality of sequencers can be deasserted via the chaining circuitry and in accordance with a second sequence. In a number of embodiments, the second sequence is a reverse order of the first sequences. The plurality of sequencers can be separate integrated circuits, and an output signal of each of the plurality of sequencers can be provided to an input of at least one of a plurality of logic gates (e.g., AND and/or OR gates) of the chaining circuitry. In a number of embodiments, the plurality of sequencers comprises at least three sequencers configured to sequence power rails in association with powering up and powering down a memory device. However, one of ordinary skill in the art will appreciate that embodiments are not limited to chaining circuitry corresponding to three (or more) sequencers. For example, two sequencers can be chained together via a sole OR gate corresponding to a first sequencer and a sole AND gate corresponding to a last sequencer in the chain. 
       FIG.  5    illustrates an example machine of a computer system  541  within which a set of instructions, for causing the machine to perform one or more of the methodologies discussed herein, can be executed. In some embodiments, the computer system  541  can correspond to a host system (e.g., the host system  120  of  FIG.  1   ) that includes, is coupled to, or utilizes a memory sub-system (e.g., the memory sub-system  110  of  FIG.  1   ) or can be used to perform the operations of a controller (e.g., to execute an operating system to perform operations corresponding to the sequencer chaining circuitry  152  and/or sequencers  153  of  FIG.  1   ). In alternative embodiments, the machine can be connected (e.g., networked) to other machines in a LAN, an intranet, an extranet, and/or the Internet. The machine can operate in the capacity of a server or a client machine in client-server network environment, as a peer machine in a peer-to-peer (or distributed) network environment, or as a server or a client machine in a cloud computing infrastructure or environment. 
     The machine can be a personal computer (PC), a tablet PC, a set-top box (STB), a Personal Digital Assistant (PDA), a cellular telephone, a web appliance, a server, a network router, a switch or bridge, or another machine capable of executing a set of instructions (sequential or otherwise) that specify actions to be taken by that machine. Further, while a single machine is illustrated, the term “machine” shall also be taken to include a collection of machines that individually or jointly execute a set (or multiple sets) of instructions to perform one or more of the methodologies discussed herein. 
     The example computer system  541  includes a processing resource  502  (e.g., a processing device), a main memory  504  (e.g., read-only memory (ROM), flash memory, dynamic random access memory (DRAM) such as synchronous DRAM (SDRAM) or Rambus DRAM (RDRAM), etc.), a static memory  506  (e.g., flash memory, static random access memory (SRAM), etc.), and a data storage system  518 , which communicate with each other via a bus  530 . 
     The processing device  502  represents one or more general-purpose processing devices such as a microprocessor, a central processing unit, or the like. More particularly, the processing device can be a complex instruction set computing (CISC) microprocessor, reduced instruction set computing (RISC) microprocessor, very long instruction word (VLIW) microprocessor, or a processor implementing other instruction sets, or processors implementing a combination of instruction sets. The processing device  502  can also be one or more special-purpose processing devices such as an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a digital signal processor (DSP), network processor, or the like. The processing device  502  is configured to execute instructions  526  for performing the operations and steps discussed herein. The computer system  541  can further include a network interface device  508  to communicate over the network  520 . 
     The data storage system  518  can include a machine-readable storage medium  524  (also known as a computer-readable medium) on which is stored one or more sets of instructions  526  or software embodying one or more of the methodologies or functions described herein. The instructions  526  can also reside, completely or at least partially, within the main memory  504  and/or within the processing device  502  during execution thereof by the computer system  541 , the main memory  504  and the processing device  502  also constituting machine-readable storage media. The machine-readable storage medium  524 , data storage system  518 , and/or main memory  504  can correspond to the memory sub-system  110  of  FIG.  1   . 
     In one embodiment, the instructions  526  include instructions  552  to implement functionality corresponding to the sequencer chaining circuitry  152  of  FIG.  1   . While the machine-readable storage medium  524  is shown in an example embodiment to be a single medium, the term “machine-readable storage medium” should be taken to include a single medium or multiple media that store the one or more sets of instructions. The term “machine-readable storage medium” shall also be taken to include a medium that is capable of storing or encoding a set of instructions for execution by the machine and that cause the machine to perform one or more of the methodologies of the present disclosure. The term “machine-readable storage medium” shall accordingly be taken to include, but not be limited to, solid-state memories, optical media, and magnetic media. 
     Some portions of the preceding detailed descriptions have been presented in terms of algorithms and symbolic representations of operations on data bits within a computer memory. These algorithmic descriptions and representations are the ways used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. An algorithm is here, and generally, conceived to be a self-consistent sequence of operations leading to a desired result. The operations are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, combined, compared, and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like. 
     It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. The present disclosure can refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system&#39;s registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage systems. 
     The present disclosure also relates to an apparatus for performing the operations herein. This apparatus can be specially constructed for the intended purposes, or it can include a general purpose computer selectively activated or reconfigured by a computer program stored in the computer. Such a computer program can be stored in a computer readable storage medium, such as, but not limited to, types of disk including floppy disks, optical disks, CD-ROMs, and magnetic-optical disks, read-only memories (ROMs), random access memories (RAMs), EPROMs, EEPROMs, magnetic or optical cards, or type of media suitable for storing electronic instructions, each coupled to a computer system bus. 
     The algorithms and displays presented herein are not inherently related to a particular computer or other apparatus. Various general purpose systems can be used with programs in accordance with the teachings herein, or it can prove convenient to construct a more specialized apparatus to perform the method. The structure for a variety of these systems will appear as set forth in the description below. In addition, the present disclosure is not described with reference to a particular programming language. It will be appreciated that a variety of programming languages can be used to implement the teachings of the disclosure as described herein. 
     The present disclosure can be provided as a computer program product, or software, that can include a machine-readable medium having stored thereon instructions, which can be used to program a computer system (or other electronic devices) to perform a process according to the present disclosure. A machine-readable medium includes a mechanism for storing information in a form readable by a machine (e.g., a computer). In some embodiments, a machine-readable (e.g., computer-readable) medium includes a machine (e.g., a computer) readable storage medium such as a read only memory (“ROM”), random access memory (“RAM”), magnetic disk storage media, optical storage media, flash memory components, etc. 
     In the foregoing specification, embodiments of the disclosure have been described with reference to specific example embodiments thereof. It will be evident that various modifications can be made thereto without departing from the broader spirit and scope of embodiments of the disclosure as set forth in the following claims. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense.