Patent Publication Number: US-2005135145-A1

Title: Synchronous flash memory device and method of operating the same

Description:
BACKGROUND OF THE INVENTION  
      This application claims the priority of Korean Patent Application No. 2003-94417, filed on Dec. 22, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.  
      1. Field of the Invention  
      This disclosure relates to a flash memory device, and more particularly, to a synchronous flash memory device that receives commands, addresses, and data in synchronization to an external system clock.  
      2. Description of the Related Art  
      Along with development of various application systems such as mobile systems, a flash memory device as a non-volatile memory device and a memory system for controlling the same have been in high demand.  
      A conventional NAND type flash memory device toggles a CLE (Command Latch Enable) signal and an ALE (Address Latch Enable) signal with a WE (Write Enable) signal to perform a write operation, and toggles the CLE signal and the ALE signal with a RE (Read Enable) signal to perform a read operation.  
      Such a conventional NAND type flash memory device operates in an asynchronous mode without being synchronized with an external system clock. In more detail, the conventional NAND type flash memory device operates in a defective synchronous mode in a manner to be synchronized with an internal signal without being synchronized with an external system clock, which requires many control signals. Accordingly, internal circuits of the conventional NAND type flash memory device are inevitably controlled in a complicated manner, which increases a probability of skew generation in chips, and requires many pins.  
     SUMMARY OF THE INVENTION  
      Embodiments of the invention provide a flash memory device which reduces a probability of skew generation in chips, improves system performance and minimizes required pins.  
      Embodiments also provide a memory system including the flash memory device.  
      Embodiments of the invention also provide methods of operating, reading data from, and programming data into the flash memory device. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:  
       FIG. 1  is a block diagram schematically showing a flash memory device according to embodiments of the invention;  
       FIG. 2  is a block diagram schematically showing a memory system including the flash memory device of  FIG. 1  according to embodiments of the invention;  
       FIG. 3  is a timing chart illustrating an example read operation of the flash memory device of  FIG. 1 ;  
       FIG. 4  is a timing chart illustrating an example program operation of the flash memory device of  FIG. 1 ;  
       FIG. 5  is a timing chart illustrating an example erase operation of the flash memory device of  FIG. 1 ; and  
       FIG. 6  is a timing chart illustrating an example cache program operation of the flash memory device of  FIG. 1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Hereinafter, embodiments of the present invention will be described in detail with reference to the appended drawings. The same reference numbers refer to the same components throughout the drawings.  
       FIG. 1  is a block diagram schematically showing a flash memory device according to the present invention.  
      Referring to  FIG. 1 , a flash memory device  100  according to embodiments of the invention includes a flash core  11 , a page buffer/column decoder  12 , a row decoder  13 , a read control block  14 , a program control block  15 , an erase control block  16 , an address control block  17 , an input/output buffer  18 , a page buffer driver  19 , a row decoder driver  20 , an interface circuit  21 , and a latency setting register  22 .  
      The flash core  11  includes a flash memory cell array. The page buffer/column decoder  12 , the row decoder  13 , the control blocks  14 ,  15 ,  16  and  17 , the input/output buffer  18 , the page buffer driver  19 , and the row decoder driver  20  are generally included in a flash memory device, and therefore detailed descriptions thereof are omitted.  
      The latency setting register  22  stores latency values and provides the stored latency values to the interface circuit  21 . Especially, the interface circuit  21  has a scheme which sequentially receives a command CMD and addresses ADDs in synchronization to an external system clock CLK after a predetermined latency is elapsed from when a chip enable signal nCE received from an external source is activated, in a read operation, in a program operation, and in an erase operation. Here, the command CMD is received in response to an invoke signal INV.  
      That is, the conventional flash memory device receives the command CMD in response to a command latch enable (CLE) signal and receives the addresses ADDs in response to an address latch enable (ALE) signal, without being synchronized to the external system clock CLK. However, the flash memory device  100  of  FIG. 1  can receive the command CMD and the addresses ADDs in synchronization to the external system clock CLK without any CLE signal or any ALE signal, in all of the read operation, the program operation, and the erase operation.  
      Also, in a read operation, the interface circuit  21  receives a command CMD and addresses ADDs, and outputs read data sequentially through an input/output (DQ) pin into an external source, in synchronization to the external system clock CLK after a predetermined second latency is elapsed from when a confirm command is received. In a program operation, the interface circuit  21  receives a command CMD and addresses ADDs, and receives program data sequentially through the input/output (DQ) pin in synchronization to the external system clock CLK after a predetermined third latency is elapsed from when a confirm command is received.  
      That is, the conventional flash memory device outputs read data to an external source through an input/output (DQ) pin in response to an RE (Read Enable) signal, and receives program data through the input/output (DQ) pin in response to a WE (Write Enable) signal. However, the flash memory device  100  of  FIG. 1  can output read data to an external source through the input/output (DQ) pin in synchronization to an external system clock CLK without the RE signal, and can receive the program data through the input/output (DQ) pin in synchronization to the external system clock CLK without the WE signal.  
      Therefore, since the flash memory device  100  does not require CLE signals, ALE signals, RE signals and WE signals, accordingly, the internal circuits of the flash memory device  100  can be simply controlled, thereby reducing the probability of skew generation in chips, improving performance, and decreasing the number of required pins.  
      In the flash memory device  100 , example sizes of program data and read data are set based on a 512-byte (+16 bytes) sector size. Accordingly, the flash memory device  100  is FAT (File Allocation Table)—compatible with a different mass memory system based on a 512-byte sector size, such as a hard-disk. Also, the flash memory device  100  can support program data and read data up to 2K bytes based on the 512-byte size.  
       FIG. 2  is a block diagram schematically showing a memory system including the flash memory device of  FIG. 1  according to embodiments of the invention.  
      Referring to  FIG. 2 , the flash memory device  100  is connected to a memory controller  200 . The memory controller  200  generates a chip enable signal nCE, an invoke signal INV, a command CMD, and addresses ADDs, and provides the generated data to the flash memory device  100 . The invoke signal INV may be generated in the flash memory device  100 .  
       FIG. 3  is an example timing chart illustrating a read operation of the flash memory device of  FIG. 1 . Referring to  FIG. 3 , an example method for reading data from the flash memory device according to embodiments of the invention will be described in detail as follows.  
      A chip enable signal nCE is activated to a logic low level. A read command CMD 1  and addresses ADD 1  through ADD 4  are received sequentially in synchronization to an external system clock CLK after a predetermined latency (N cycle) is elapsed from when the chip enable signal nCE is activated. Thus, in the state that a signal RnB is low, data is read from the flash memory cell array in the flash memory device and stored in a latch.  
      Then, the signal RnB is changed to a logic high level and a confirm command CMD 2  is received. Read data DATA 0  through DATA 527  stored in the latch is output to outside the flash memory device through the data input/output (DQ) pin, in synchronization to the external system clock CLK after a predetermined latency (M cycle) is elapsed from when the confirm command CMD 2  is received.  
      Here, the read command CMD 1  and the confirm command CMD 2  are received in the state that the invoke signal INV is activated. The latency (N cycle) and the latency (M cycle) can be changed as necessary.  
       FIG. 4  is a timing chart illustrating an example program operation of the flash memory device of  FIG. 1  according to embodiments of the invention. Referring to  FIG. 4 , a method for programming data in the flash memory device will be described in detail as follows.  
      A chip enable signal nCE is activated to a logic low level. A program command CMD 3  and addresses ADD 1  through ADD 4  are received sequentially in synchronization to an external system clock CLK after a predetermined latency (N cycle) is elapsed from when the chip enable signal nCE is activated.  
      Then, a confirm command CMD 4  is received. Program data DATA 0  through DATA 527  are received sequentially through a data input/output (DQ) pin from an external source in synchronization to the external system clock CLK after a predetermined latency (M cycle) is elapsed from when the confirm command CMD 4  is received. Then, a signal RnB is changed to a logic low state. The program data is programmed into the flash memory cell array in the flash memory device during the state that the signal RnB is low. When the programming operation is complete, the signal RnB is changed to a logic high level to wait a next command.  
      The program command CMD 3  and the confirm command CMD 4  are received in the state that the invoke signal INV is activated. The latency (N cycle) and the latency (M cycle) can be changed as necessary.  
       FIG. 5  is a timing chart illustrating an example erase operation of the flash memory device of  FIG. 1  according to embodiments of the invention. Referring to  FIG. 5 , a method for erasing data stored in the flash memory device will be described in detail as follows.  
      A chip enable signal nCE is activated to a logic low level. An erase command CMD 5  and addresses ADD 1  through ADD 4  are received sequentially in synchronization to an external system clock CLK after a predetermined latency (N cycle) is elapsed from when the chip enable signal nCE is activated.  
      Thereafter, a confirm command CMD 6  is received. A signal RnB is changed to a logic low level after the confirm command CMD 6  is received. In the state that the signal RnB is low, data stored in the flash memory device is erased. When the erasing operation is complete, the signal RnB is changed to a logic high level to wait a next command.  
      The erase command CMD 5  and the confirm command CMD 6  are received during the state that the invoke signal INV is activated. The latency (N cycle) can be changed as necessary.  
       FIG. 6  is a timing chart illustrating an example cache program operation of the flash memory device of  FIG. 1  according to embodiments of the invention. Referring to  FIG. 6 , a cache program method of the flash memory device will be described in more detail as follows.  
      A chip enable signal nCE is activated to a logic low level. A cache program command CMD 7  and addresses ADD 1  through ADD 4  are received sequentially in synchronization to an external system clock CLK after a predetermined latency is elapsed from when the chip enable signal nCE is activated.  
      Then, a confirm command (not shown) is received. Program data D 0  through D 527  are received sequentially from an external source through a data input/output (DQ) pin, in synchronization to an external system clock CLK after a predetermined latency is elapsed from when the confirm command is received. Next, a signal RnB is changed to a logic low state, and the program data is programmed into the flash memory cell array inside the flash memory device during the state that the signal RnB is low.  
      Thereafter, the signal RnB is changed to a logic high level by a command CMD 8 , and then a program command CMD 9  and addresses ADD 1  through ADD 4  are received sequentially. Thus, another set of program data D 0  through D 527  are received sequentially from an external source through the data input/output (DQ) pin in synchronization to the external system clock CLK after a predetermined latency is elapsed. Then, the signal RnB is again changed to a logic low level. The second set of program data is programmed into the flash memory cell array inside the flash memory device during the state that the signal RnB is low, and then the cache program operation is terminated.  
      Of course, the above description of embodiments of the invention can be practiced in various ways without deviating from the inventive scope of the invention. What follows are descriptions of particular, non-limiting example embodiments.  
      According to an embodiment of the invention, there is provided a non-volatile memory device including: a non-volatile memory cell array; and an interface circuit, which receives a command and addresses sequentially, in synchronization to an external system clock after a predetermined first latency is elapsed from when a chip enable signal is activated, in a read operation, in a program operation, and in an erase operation.  
      The interface circuit receives the command in response to activation of an invoke signal. The interface circuit outputs read data sequentially to the outside of the non-volatile memory device in synchronization to the external system clock after a predetermined second latency is elapsed from when a confirm command is received after the command and the addresses are received, in the read operation.  
      The interface circuit receives program data sequentially in synchronization to the external system clock after a predetermined second latency is elapsed from when a confirm command is received after the command and the addresses are received, in the program operation. The interface circuit receives the confirm command in response to activation of the invoke signal.  
      According to another embodiment of the invention, there is provided a memory system including: a memory controller; and a non-volatile memory device which is connected to the memory controller, wherein the non-volatile memory device includes, a non-volatile memory cell array, and an interface circuit, which receives a command and addresses sequentially, in synchronization to an external system clock after a predetermined first latency is elapsed from when a chip enable signal is activated, in a read operation, in a program operation and in an erase operation, wherein the memory controller provides the chip enable signal, the command, and the addresses.  
      The interface circuit receives the command in response to activation of an invoke signal.  
      The interface circuit outputs read data sequentially to an external source, in synchronization to the external system clock after a predetermined second latency is elapsed from when a confirm command is received after the command and the addresses are received, in the read operation.  
      The interface circuit receives program data sequentially, in response to the external system clock after a predetermined second latency is elapsed from when a confirm command is received after the command and the addresses are received, in the program operation.  
      The interface circuit receives the confirm command in response to activation of the invoke signal.  
      The memory controller provides the confirm command and the invoke signal is generated in the non-volatile memory device.  
      According to still another embodiment of the invention, there is provided a method for operating a non-volatile memory device including: activating a chip enable signal; and sequentially receiving a command and addresses sequentially in synchronization to an external system clock after a predetermined latency is elapsed from when the chip enable signal is activated.  
      The command is received in response to activation of an invoke signal.  
      According to another embodiment of the invention, there is provided a method for reading data from a non-volatile memory device, the method including: activating a chip enable signal; sequentially receiving a command and addresses in synchronization to an external system clock after a predetermined first latency is elapsed from when the chip enable signal is activated; receiving a confirm command after the command and the addresses are received; and outputting read data sequentially to the outside of the non-volatile memory device, in synchronization to the external system clock after a predetermined second latency is elapsed from when the confirm command is received.  
      The command and the confirm command are received in response to activation of an invoke signal.  
      According to another embodiment of the invention, there is provided a method for programming data in a non-volatile memory device, the method including: activating a chip enable signal; receiving a command and addresses sequentially in synchronization to an external system clock after a predetermined first latency is elapsed from when the chip enable signal is activated; receiving a confirm command after the command and the addresses are received; and receiving program data sequentially in synchronization to the external system clock after a predetermined second latency is elapsed from when the confirm command is received.  
      The command and the confirm command are received in response to activation of an invoke signal.  
      As described above, since the flash memory device  100  according to the present invention does not require CLE signals, ALE signals, RE signals and WE signals, internal circuits of the flash memory device  100  can be simply controlled, thereby reducing a probability of skew generation in chips, improving performance, and decreasing the number of required pins.  
      While the invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.