Abstract:
A semiconductor memory device includes a cell core storing data, a plurality of peripheral circuit components, collectively driving data to/from the cell core and providing a default state at an output signal state during an initialization process upon power-up, and an initialization circuit detecting a standby mode of operation for the semiconductor memory device, and upon detecting the standby mode controlling operation of the plurality of peripheral circuit components to provide the default state as the signal state during standby mode.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
       [0001]    This application claims the benefit of Korean Patent Application No. 10-2007-0130981 filed on Dec. 14, 2007, the subject matter of which is hereby incorporated by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates generally to semiconductor devices, and more particularly to semiconductor memory devices having reduced standby failures. 
         [0004]    2. Description of the Related Art 
         [0005]    Standby failure occurs when current leakage through a current path in an integrated circuit persists following a defined operating mode. Under these circumstances, the current leakage wastes power, which is particularly detrimental to mobile electronics incorporating the semiconductor device, and may be erroneously interrupted as a signal within the semiconductor device. 
         [0006]    For example, semiconductor memory devices include a cell core and one or more related peripheral circuits. Common operating modes for contemporary semiconductor memory devices include an active mode and a standby mode. In active mode, data may be written to or read from memory cells in the cell core by controlled operation of the related peripheral circuits. However, in standby mode, the peripheral circuits are specifically disabled in order to reduce power consumption within the semiconductor memory device. Thus, a standby failure occurring in such peripheral circuits defeats, as least in part, the primary purpose of the standby operating mode. 
         [0007]      FIG. 1  is a circuit diagram illustrating a relevant portion of a peripheral circuit  100  in a conventional semiconductor memory device. As shown in  FIG. 1 , peripheral circuit  100  receives a clock signal CLK and a plurality of data signals D 0 , D 1 , . . . Dn. During a write operation, the peripheral circuit will drive the plurality of signals onto signal lines connected to memory cells on the cell core of the semiconductor memory device (not shown). In order to drive the plurality of data signals to the cell core, a relatively large number of peripheral circuit components must be used. These components perform various, well-understood functions and may be variously implemented and operated within the semiconductor memory device. Generally speaking, however, many of the peripheral circuit components will include a combination or sequential logic circuit operating in relation to one or more input signals and providing a corresponding output. Many of the peripheral circuit components also include one or more flip-flop circuits. 
         [0008]    Referring to the collection of peripheral circuit components  100  shown in  FIG. 1 , when power is applied to the constituent semiconductor memory device, an initialization process is performed. During the initialization process, defined “set” (SN) and “reset” (RN) are generated upon detection of the applied power. As the set/reset signals are applied to the peripheral circuit components during the initialization process, default state outputs are provided by the peripheral circuit components. A test process may be applied to the semiconductor memory device during a first (or each) initialization process. During the test process, a predetermined data pattern is applied to the collection of peripheral circuit components  100 . With the predetermined data pattern applied, the current consumption of the semiconductor memory device is measured and a determination is made regarding whether or not excessive current leakage is present (i.e., whether a standby failure has occurred). However, this static default condition testing is often unable to accurately identify current leakage associated with mode transitions within the semiconductor memory device. 
         [0009]      FIG. 2  illustrates one example of current leakage occurring in the peripheral circuit components  100  of  FIG. 1  in relation to an operating mode transition. Following a read/write operation performed by the semiconductor memory device, the data output state for the individual peripheral circuit components  110 ,  120  and  130  will have random values as the semiconductor memory device enters a subsequent standby mode. For example, if an electrical connection exists between the output of a first peripheral circuit component  110  and a first external signal line, a current path may exist, depending on the residual data state apparent at the output (i.e., its residual voltage state as defined by the last read/write operation) and the voltage level apparent on the first external signal line. Current paths formed in the direction of the illustrated arrows shown in  FIG. 2  may exist given the respective residual data states of the first, second and third peripheral circuit components  110 ,  120  and  130 . Thus, since a “low” data state (and a corresponding low voltage) is apparent at the output of the NAND gate of the first and third peripheral circuit components  110  and  130 , a current path may be formed when the first or third external signal lines is respectively connected to a “high” voltage source. In similar vein, since a “high” data state (and a corresponding high voltage) is apparent at the output of the NOR gate of the second peripheral circuit component  120 , a current path may be formed when the second external signal line is connected to a “low” voltage source (i.e., ground). 
         [0010]    Thus, even where current leakage in peripheral circuit components is not detected during initialization testing under static default conditions, a standby failure may nonetheless occur when certain residual data values are apparent at the outputs of the peripheral circuit components, when said outputs are connected to external signal lines coincidentally connected to a mismatched power voltage, for example. Under these dynamic, data-sensitive conditions arising from a previously performed active mode operation, a standby failure may arise that consumes excessive power and reduces overall battery life in portable electronics incorporating the semiconductor device. 
       SUMMARY OF THE INVENTION 
       [0011]    Embodiments of the present invention provide a semiconductor device having a reduced occurrence of standby failures. 
         [0012]    In one embodiment, the invention provides a semiconductor memory device comprising; a cell core storing data, a plurality of peripheral circuit components, collectively driving data to/from the cell core and providing a default state at an output signal state during an initialization process upon power-up, and an initialization circuit detecting a standby mode of operation for the semiconductor memory device, and upon detecting the standby mode controlling operation of the plurality of peripheral circuit components to provide the default state as the signal state during standby mode. 
         [0013]    In another embodiment, the invention provides a semiconductor device comprising; a plurality of logic circuits respectively generating output data in response to control signals provided by an initialization circuit, wherein the control signals provided by the initialization circuit upon power-up detection define a default state for the output data generated by the plurality of logic circuits, and upon detecting a standby state of operation for the semiconductor device, providing control signals from the initialization circuit to again define the default state for the output data generated by the plurality of logic circuits. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a circuit diagram illustrating certain peripheral circuit components within a conventional semiconductor memory device; 
           [0015]      FIG. 2  further illustrates possible current leakage occurring at the peripheral circuit components of  FIG. 1 ; 
           [0016]      FIG. 3  illustrates an exemplary collection of peripheral circuit components in a semiconductor device according to an embodiment of the invention; 
           [0017]      FIG. 4  is a block diagram further illustrating the initialization circuit of the semiconductor device shown in  FIG. 3 ; and 
           [0018]      FIG. 5  is a waveform diagram illustrating operation of a semiconductor device according to an embodiment of the invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0019]    Several embodiments of the invention will now be described with reference to the accompanying drawings. The invention may however be variously embodied and should not be construed as being limited to only the illustrated embodiments. Throughout the specification like reference numerals and indicators are used to denote like or similar elements. 
         [0020]      FIG. 3  illustrates an exemplary collection of peripheral circuit components within a semiconductor device according to an embodiment of the invention. The semiconductor device illustrated in  FIG. 3  may be, e.g., a semiconductor memory device. 
         [0021]    As illustrated in  FIG. 3 , a semiconductor memory device  200  comprises a plurality of peripheral circuit components  210  respectively generating output data signals that are conventionally driven onto signal lines associated with a cell core (not shown). The small plurality of peripheral circuit components  210  is merely illustrative of a much larger plurality of variously configured peripheral circuit components that will be used in any practical implementation of the present invention. However, in the illustrated example, the plurality of peripheral circuit components  210  receives data signals D[0:n] and a clock signal CLK from an external controller and generates corresponding output data signals subsequently applied to the cell core during (e.g.,) read, write and erase operations. 
         [0022]    The plurality of peripheral circuit components  210  is shown with individual circuit components  211 ,  212  and  213 , respectively receiving a first (D 0 ), a second (D 1 ) and an nth (Dn) input data signal at a data input “D” of a flip-flop circuit (F/F). Set (SN) and reset (RN) signals are variously applied to the respective flip-flops, and the clock signal CLK is applied to each clock input of each flip-flop. In response to a particular application of set/reset, clock and data signals, each flip-flop (F/F) generates an output data signal at a data output “Q”. The data output signal Q is then applied as an input to combinational and sequential logic circuits to yield a respective data output signal for each peripheral circuit component  211 ,  212  and  213 . Only simple examples of logic circuits (e.g., each flip-flop together with a logic gate receiving an input signal from generically indicated “combination logic”) are shown in  FIG. 3 , but those skilled in the art will understand that such circuitry will vary by input and configuration with design. 
         [0023]    Thus, the logic circuitry within each peripheral circuit component  211 ,  212  and  213  generates output data in synchronization with the applied clock signal CLK, and having a data state determined by the applied input data, reset signal RN and/or set signal SN. 
         [0024]    Semiconductor memory device  200  also comprises an initialization circuit  220 . When power is applied to semiconductor memory device  200 , an initialization process is performed. Initialization circuit  220  detects the application of power to semiconductor memory device  200 , and activates the reset signal RN and/or the set signal SN in a defined manner in response to the power detection. Thus, the initialization process is characterized by the selective application of the reset signal RN and/or set signal SN to each peripheral circuit component  211 ,  212  and  213 . 
         [0025]    The defined application of the reset signal RN and/or set signal SN to each peripheral circuit component  211 ,  212  and  213  during the initialization process, results in the generation of respective “default state” outputs by the plurality of peripheral circuit components  210 . A leakage current test process may then be applied to semiconductor memory device  200  by applying a predetermined input data pattern to the plurality of peripheral circuit components  210 . This type of static leakage current testing is conventional, but will nonetheless reveal certain types of fabrication failures commonly associated with contemporary semiconductor devices. 
         [0026]    However, as discussed above, more complete testing is required to ensure the absence of a standby failure. That is, the very precise fabrication processes used to form the very small and very densely integrated elements of contemporary semiconductors may result in standby failures that are not revealed during conventional, static current leakage testing. Some fabrication (or design) failures may actually result in an inadvertent connection (e.g., a conductive bridge) between a peripheral circuit component output and one or more external signal lines. Such inadvertent connections may not be revealed during static current leakage testing, but will nonetheless yield standby failures during dynamic operation of the semiconductor device. That is, the output data value for each component in the plurality of peripheral circuit components  210  may change in relation to various active mode operations (e.g., read/write and erase operations), and different output data values and standby current leakage, as has been seen above, is often a function of output data value in relation to the voltage applied to the bridge-connected external signal line. The term “external signal line” in this context refers to any electrically conductive element outside a peripheral circuit component. 
         [0027]    To reduce the incidence of standby failures, initialization circuit  220  provided in semiconductor memory device  200  according to embodiments of the invention is adapted to detect various operating modes for semiconductor memory device  200 , and change the output data value for each peripheral circuit component  211 ,  212 , and  213  in relation to the detected operating mode. Initialization circuit  220  may be adapted to detect one or more operating modes, such as a write (or program) operation, a read operation, and/or an erase operation or another type of active mode or a standby mode associated with a particular type of semiconductor memory device  200 . 
         [0028]    If the detection result indicates a standby mode, the data output values for the plurality of peripheral circuit components  210  is defined such that current leakage does not occur. For example, initialization circuit  220  may activate/deactivate the reset signal RN and/or the set signal SN applied to the plurality of peripheral circuit components in accordance with the detected operating mode, such that the data output values provided by the plurality of peripheral circuit components  210  is identical to that of the default state established during the initialization process. 
         [0029]      FIG. 4  is a block diagram further illustrating one example of initialization circuit  220  shown in  FIG. 3 . As shown in  FIG. 4 , initialization circuit  220  comprises a power detector  221  and an operating mode detector  222 . To control the output data values provided by the plurality of peripheral circuit components  210  in accordance with the detection results of initialization circuit  220 , initialization circuit  220  may further comprise a set/reset signal generator  223  activating/deactivating the reset signal and/or the set signal provided to the plurality of peripheral circuit components  210 . 
         [0030]    Power detector  221  detects power initially applied to semiconductor memory device  200 , generates a first control signal C 1  in accordance with the detection result, and provides the first control signal C 1  to set/reset signal generator  223 . Operating mode detector  222  detects whether the current operating mode of semiconductor memory device  200  is a standby mode by, for example, tracking the completion of one or more active operating modes (e.g., write/program, read and erase operations) within semiconductor memory device  200 . Based on a detection of the current operating mode, mode detector  222  generates a second control signal C 2 , and provides the second control signal C 2  to set/reset signal generator  223 . 
         [0031]    Set/reset signal generator  223  activates/deactivates the set SN and reset RN signals in response to the first and second control signals C 1  and C 2 . Although set and reset signals applied to flip-flop circuits have been described in the foregoing example, other control signals and/or particular logic circuit inputs may be used in other embodiments of the invention. That is, when initial power is applied to semiconductor memory device  200 , set/reset signal generator  223  provides the reset signal RN or the set signal SN to each peripheral circuit component  211 ,  212  and  213 , such that the output state of the plurality of peripheral circuit components  210  becomes the default state. In one embodiment of the invention, it is assumed that the reset signal RN and set signal SN are deactivated during active operating modes, during which data is written to or read from the cell core of semiconductor memory device  200 . In contrast, when semiconductor memory device  200  operates in standby mode, set/reset signal generator  223  activates the reset signal RN and/or the set signal SN, such that the output data values provided by the plurality of peripheral circuit components  210  assumes the default state (i.e., the same state as was assumed during initialization testing). In this manner, semiconductor memory device  200  runs in standby mode with output data values similar to the output data values defined during initialization testing. Thus, the initialization testing accurately reflects the current leakage occurring during the standby mode of operation. And since the output data values are “don&#39;t care” values during the standby mode, no adverse data effects will arise in semiconductor memory device  200 . 
         [0032]    In the foregoing description, the output data values (or output state) for the plurality of peripheral circuit components  210  is changed to a defined default state associated with an initialization testing process when semiconductor memory device  200  is in a standby mode. However, the scope of present invention is not limited to only this specific approach. For example, the output state of the plurality of peripheral circuit components  210  during the standby mode may be defined to be a specific data pattern that prevents current leakage. A circuit to implement this particular adaptation of the invention may be easily realized by those skilled in the art in view of the foregoing disclosure. 
         [0033]      FIG. 5  is a waveform diagram describing overall operation of a semiconductor memory device according to an embodiment of the present invention. 
         [0034]    As illustrated, the application of power to the semiconductor memory device is detected, and corresponding peripheral circuits driving data to/from the cell core are initialized. That is, once power-up is detected, a reset signal RN and/or a set signal SN is activated and provided to at least one of a plurality of peripheral circuit components. In response, the output signal state of the plurality of peripheral circuit components becomes a default state. 
         [0035]    When data and clock signals are provided to the plurality of peripheral circuit components during an active mode of the semiconductor memory device, an operation driving data to/from the cell core may be performed. Following such operations, the semiconductor memory device may assume a standby mode. When the standby mode is detected, the reset signal RN and/or the set signal SN are again activated/deactivated in a manner such that the signal state of the plurality of peripheral circuits in the standby mode becomes the default state. Accordingly, standby failure of the semiconductor memory device is effectively prevented or significantly reduced in occurrence. 
         [0036]    In the above description, the semiconductor memory device is mainly described. However, the present invention is not limited thereto, and embodiments of the invention may be applicable to many types of semiconductor devices, not just memory devices. That is, many semiconductor devices include a plurality of logic circuit blocks that implement a defined function. A reset signal and/or a set signal are applied to one or more of these logic circuit blocks when power is first applied to the semiconductor device during an initialization to define a default state, and thereafter certain standby modes of operation are detected and said logic circuit blocks are operated to assume the same default state. 
         [0037]    While the present 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 scope of the present invention as defined by the following claims.