Abstract:
An integrated circuit device includes a pin for receiving a DC voltage component signal. The device includes a signal source for applying an AC signal to the pin, a buffer for converting the AC signal into a digital signal, and a digital detector for detecting a frequency of the digital signal and outputting a predetermined detection signal. The predetermined detection signal is activated when the frequency of the digital signal is greater than or equal to a predetermined frequency. The predetermined detection signal is used as a signal for setting predetermined functional modes. The device further includes registers or a differential amplifier and a decoder for generating a plurality of functional mode signals.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a semiconductor integrated circuit, and more particularly, to a semiconductor integrated circuit comprising functional modes. 
   2. Description of the Related Art 
   Semiconductor integrated circuits employ functional modes in which device characteristic analysis and reliability verification are performed. Further, by using functional modes a test time and/or a burn-in test time can be reduced in a packaging process. The analysis, verification, and test functions are performed through joint test action group (JTAG) pins available to designers, or function command cells. However, a designer cannot set a desired function in a package without a pin and control code being made available during the packaging process. 
   SUMMARY OF THE INVENTION 
   According to an embodiment of the present invention, a semiconductor integrated circuit with functional modes substantially obviates one or more limitations and disadvantages of the related art. 
   It is an object of the present invention to provide a semiconductor integrated circuit with functional modes in which designers can set a desired function without a dedicated pin. 
   It is another object of the present invention to provide a semiconductor integrated circuit with functional modes in which a functional mode can be set easily and flexibly. 
   Additional advantages, objects, and features of the invention will be set forth in part in the description which follows. The advantages, objects, and features of the present invention will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description, including the drawings, and claims. 
   According to an embodiment of the present invention, an integrated circuit device comprises a pin that receives a direct current (DC) voltage component signal. The device includes a signal source for applying an alternating current (AC) signal to the pin, a buffer for converting the AC signal into a digital signal, and a digital detector for detecting a frequency of the digital signal and outputting a predetermined detection signal. 
   The predetermined detection signal is activated when the frequency of the digital signal is greater than or equal to a predetermined frequency. The predetermined detection signal is used as a signal for setting a predetermined functional mode. 
   To generate a plurality of functional mode signals, the device according to the present invention further includes a register chain for generating successive transfer signals according to the digital signal in response to a clock signal, and a decoder for generating functional mode signals according to the transfer signals in response to the predetermined detection signal. The decoder generates the functional mode signals through a logical combination of the transfer signals. 
   According to an embodiment of the present invention, an integrated circuit device comprises a pin that receives a DC voltage component signal. The device comprises differential amplifiers for comparing a DC voltage component signal applied to the pin with a reference voltages and generating differential amplification signals. The device further comprises a decoder for generating at least one functional mode signal according to a logical combination of the differential amplification signals. The reference voltages are between a lowest voltage level of a plurality of high level voltages of the integrated circuit device and a highest voltage level of a plurality of low level voltages of the integrated circuit device. 
   According to an embodiment of the present invention, an integrated circuit device comprising a pin for receiving a direct current voltage component signal, the device comprises a pin for receiving an alternating current signal, a buffer coupled to the pin for converting the alternating current signal into a digital signal, and a digital detector coupled to the buffer for detecting a frequency of the digital signal and outputting a functional mode signal for setting a mode of the device. The digital detector comprises a plurality of inverter stages responsive to a reference signal. Each inverter stage comprises a PMOS transistor and an NMOS transistor coupled in series to the PMOS transistor, the NMOS transistor having a size smaller than a size of the PMOS transistor. The functional mode signal depends on the size of the NMOS transistor for pull-down. The functional mode signal is activated when the frequency of the digital signal is greater than a predetermined minimum frequency. The predetermined minimum frequency depends on a size of an NMOS transistor relative to a PMOS transistor in an inverter stage of the digital detector. 
   The semiconductor integrated circuit device is an SRAM device. The SRAM device is, for example, a 100-pin low profile quad flat package (100-pin LPQFP) type SRAM, a no-turnaround RAM (NtRAM), and a synchronous pipelined burst (SPB) type SRAM having a DC pin to set operation modes. 
   The DC pins employed in the semiconductor integrated circuit device comprise a mode setting pin, or pad, for logically setting a level to be a high level or a low level, a power supply voltage VDD pin, and a ground voltage (GND) pin. The mode setting pin is exemplified by the pin LBOB that is set to be a high logic level (“1”: linear manner) or a low logic level (“0”: interactive manner) to determine burst data processing order in 100-pin LQFP type SRAM. The mode setting pin can be used in various embodiments. However, it should be noted that the power supply voltage pin and ground voltage pin can be used where the pins do not affect on the supply of electric power. 
   It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory, and are intended to provide further explanation of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred embodiments of the present invention will be described below in more detail, with reference to the accompanying drawings: 
       FIG. 1  is a block diagram of an operation mode setting circuit according to an embodiment of the present invention; 
       FIG. 2  is a circuit showing an embodiment of a frequency detector shown in  FIG. 1 ; 
       FIG. 3  illustrates a waveform representing input/output characteristic of the frequency detector shown in  FIGS. 1  or  2 ; 
       FIG. 4  is a block diagram of an operation mode setting circuit according to an embodiment of the present invention; 
       FIG. 5  is a diagram illustrating a circuit of a decoder shown in  FIG. 4 ; 
       FIG. 6  illustrates waveforms showing output characteristic of the decoder shown in  FIG. 5 ; 
       FIG. 7  is a block diagram of an operation mode setting circuit according to an embodiment of the present invention; and 
       FIG. 8  is a state diagram illustrating voltage levels of reference voltages shown in FIG.  7 . 
     Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   Reference will now be made in detail to preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. However, the present invention is not limited to the embodiments illustrated, and the embodiments are rather introduced to provide easy and complete understanding of the scope and spirit of the present invention. 
   Referring to  FIG. 1 , in a functional mode setting circuit comprises a pin or pad  10  connected to a frequency detector  30  through a buffer  20 . An AC signal S 1 , input through the pin  10 , is converted into a digital signal S 2  by the buffer  20  having a complementary metal-oxide-semiconductor (CMOS) logic. The digital signal S 2  is applied to the frequency detector  30 . As shown in  FIG. 3 , the frequency detector  30  outputs a functional mode signal FM 0  if the digital signal S 2  oscillates between a high level and a low level for a predetermined duration. 
   The frequency detector  30  is configured as shown in FIG.  2 . The CMOS digital signal S 2  provided from the buffer  20  is applied to the gates of a PMOS transistor P 1  and an NMOS transistor N 1  through inverters I 1  and I 2  connected in series. The PMOS transistor P 1  and the NMOS transistor N 1  are connected to each other in series between a power supply voltage VDD and an NMOS transistor N 2 . The NMOS transistor N 2  is connected to the NMOS transistor N 1  and a ground voltage GND. The gate of the NMOS transistor N 2  is connected to a reference signal REF. When the reference signal REF is activated, the PMOS transistor P 1  and the NMOS transistor N 1  operate. The reference signal REF is at such a voltage level as to turn the NMOS transistor N 2  on. Node  31  is connected to the drain of the PMOS transistor P 1  and the source of the NMOS transistor N 1 , and is connected to the gates of a PMOS transistor P 2  and an NMOS transistor N 3  through an inverter I 3 . The NMOS transistor N 3  is connected to the ground voltage GND through an NMOS transistor N 4 . The gate of the NMOS transistor N 4  and the gate of the NMOS transistor N 2  are connected to the reference signal REF. Similarly, the PMOS transistor P 2  and the NMOS transistor N 3  act as an inverter when the NMOS transistor N 4  is turned on in response to the reference signal REF. Node  32  is connected to the drain of the PMOS transistor P 2  and the source of the NMOS transistor N 3 , and is connected to the input of a NOR gate NR 1  through an inverter  14 . 
   The digital signal S 2  is applied to the gates of a PMOS transistor P 3  and an NMOS transistor N 5  through an inverter  15 . The PMOS transistor P 3  and the NMOS transistor N 5  are connected to each other in series between the power supply voltage VDD and an NMOS transistor N 6 . The NMOS transistor N 6  is connected to the NMOS transistor N 5  and the ground voltage GND. The gate of the NMOS transistor N 6  is connected to the reference voltage REF. When the reference signal REF is activated, the PMOS transistor P 3  and the NMOS transistor N 5  act as an inverter. Node  33  is connected to the drain of the PMOS transistor P 3  and the source of the NMOS transistor N 5 , and is connected to the gates of a PMOS transistor P 4  and an NMOS transistor N 8  through an inverter I 9 . The NMOS transistor N 8  is connected to the ground voltage GND through an NMOS transistor N 9 . The gate of the NMOS transistor N 9  and the gate of the NMOS transistor N 6  are connected to the reference signal REF. Similarly, the PMOS transistor P 4  and the NMOS transistor N 8  act as an inverter in response to the reference signal REF when the NMOS transistor N 9  is turned on. Node  34  connected to the drain of the PMOS transistor P 4  and the source of the NMOS transistor N 8 , and is connected to the input of the NOR gate NR 1  through an inverter I 10 . 
   NMOS transistors N 1  to N 9  are smaller in size than other MOS transistors (for example, PMOS transistors P 1  to P 4 ). Accordingly, the NMOS transistors N 1  to N 9  have a low current driving power. The operation of the NMOS transistors will be described in detail with reference to FIG.  3 . Referring to  FIG. 2 , two NMOS transistors (for example, N 1  and N 2 ) are connected to each other in series in each inverter stage, but it should be noted that each inverter stage can be configured with one NMOS transistor, for example, N 1 , connected to a PMOS transistor, for example, P 1 . 
   The NOR gate NR 1  receives the outputs of the inverters I 4  and I 10  and outputs a functional mode signal FM 0  through inverters I 11  and I 12  connected in series. 
   Referring to  FIG. 3 , when the signal S 2  is fixed at a high level or a low level (Tx), the functional mode FM 0  is generated at a low level. When the signal S 2  is fixed at high level, nodes  32  and  33  go to a low level and a high level respectively. As the outputs A and B of the inverters I 4  and I 10  go to a high level and a low level respectively, the output of the NOR gate NR 1  goes to a low level and the functional mode signal FM 0  goes to a low level. When the signal S 2  is fixed at a low level, the functional mode signal FM 0  is fixed at a low level as the outputs of the inverters I 4  and I 10  go to a low level and a high level respectively. 
   However, the digital signal S 2  is responsive to an oscillation of the AC signal S 1  applied to the pin  10  with at least a predetermined frequency(Tf), causing the functional mode signal FM 0  to be activated to a high level. As described above, if the signal S 2  oscillates between a high level and a low level with at least a predetermined frequency (Tf), the pulse width of the high level of the output A′ of the inverter  13  is short even though S 2  is at a high level since the current driving power of the NMOS transistors N 1  and N 2  is small. The NMOS transistors N 1  and N 2  with the low current driving power react slowly to a signal having a high level. Similarly, since each of the NMOS transistors N 3  and N 4  in a next stage has a low current driving power, the low level response to shortened high level pulse components does not appear at the node  32 . As a result, at the input A of the NOR gate NR 1 , only a low level signal appears for the duration Tf in which S 2  oscillates with at least a predetermined frequency. In addition, on the path from inverter I 5  to the input B of the NOR gate NR 1 , the pulse width of the high level portions of the signal S 2  becomes shorter and only a low level signal appears at the input B according to the same process. As a result, for example, the functional mode signal FM 0  is maintained to be high level while the signal S 2  oscillates with at least a predetermined frequency (Tf). The functional mode signal FM 0  detected to be at a high level during the duration Tf drives predetermined inner circuits of an integrated circuit device to perform a test operation and the like. If the signal S 2 , or S 1 , oscillates with at least a predetermined frequency, activation of the functional mode signal FM 0 , e.g., FM 0  has a high level, depends on the size of the NMOS transistors N 1  to N 9  for pull-down. In addition, as shown in  FIG. 2 , it should be noted that the high level pulse width can be shortened. 
   On the other hand, when the signal S 2  oscillates with at most a predetermined frequency, the functional mode signal FM 0  also oscillates in response to the signal S 2 . However, the frequency of the signal S 2  may not be used. 
   The circuit configuration and input/output characteristics of the frequency detector  30  shown in  FIGS. 2 and 3  are used in an embodiment to be described. 
   According to an embodiment of the present invention, the functional mode setting circuit shown in  FIG. 4  uses the configuration shown in  FIG. 1  to generate a plurality of functional mode signals. Referring to  FIG. 4 , CMOS digital signal S 2  output from a buffer  20  is applied to a frequency detector  30  and transferred to a register chain comprising registers REG 1  to REG 4  connected in series. The registers REG 1  to REG 4  send respective outputs R 1  to R 4  to a decoder  40  in response to a clock signal CLK that has a predetermined frequency and a predetermined synchronous period. Whenever the clock signal CLK passes one period, the signal S 2  passes each register stage. Each register is used in, for example, a general delay loop and a general phase loop. Each register includes a latch comprising a pair of inverters and a transfer gates turned on or off in response to the clock signal CLK. 
   As mentioned above with respect to  FIG. 3 , a frequency detector  30  generates a functional mode signal FM 0  having a high level when a signal S 2  oscillates with at least a predetermined frequency, e.g., it represents that the signal input state to set a functional mode is valid. In  FIG. 4 , the signal FM 0  is used in controlling the decoder  40 . The decoder  40  receives transfer signals R 1  to R 4  from registers REG 1  to REG 4  and generates functional mode signals FM 1  to FM 3  while the signal FM 0  is at a high level. 
   In  FIG. 4 , there are four registers and three functional mode signals but the number of function mode signals can depend on the desired functions. 
   Referring to  FIG. 5 , a decoder  40  comprises NAND gates ND 1  to ND 17  for responding to a combination of the register transfer signals R 1  to R 4 . Methods for generating the function mode signal according to the combinations of R 1  to R 4  can vary. According to an embodiment of the present invention, the functional mode signal FM 1  is activated when one of the transfer signals R 1  to R 4  has a high level. The functional mode signal FM 2  is activated when two of the transfer signals R 1  to R 4  have a high level. The functional mode signal FM 3  is activated when three of the transfer signals R 1  to R 4  have a high level. The signals R 1 B to R 4 B are inverse logic signals of the transfer signals R 1  to R 4 . 
   The NAND gate ND 1  receives R 1 , R 2 B, R 3 B, and R 4 B. The NAND gate ND 2  receives R 1 B, R 2 , R 3 B, and R 4 B. The NAND gate ND 3  receives R 1 B, R 2 B, R 3 , and R 4 B. The NAND gate ND 4  receives R 1 B, R 2 B, R 3 B, and R 4 . The outputs of the NAND gates ND 1  to ND 4  are input to the NAND gate ND 15 . The NAND gate ND 15  generates the functional mode signal FM 1 . Since the other inverse logic signals remain at a high level while one of the transfer signals R 1  to R 4  is at a high level, one of the outputs of the NAND gates ND 1  to ND 4  goes to a low level, and the NAND gate ND 15  generates the activated functional mode signal FM 1  having a high level. 
   The NAND gate ND 6  receives R 1 , R 2 B, R 3 , and R 4 B. The NAND gate ND 7  receives R 1 , R 2 B, R 3 B, and R 4 . The NAND gate ND 8  receives R 1 B, R 2 , R 3 , and R 4 B. The NAND gate ND 9  receives R 1 B, R 2 , R 3 B, and R 4 . The NAND gate ND 10  receives R 1 B, R 2 B, R 3 , and R 4 . The outputs of the NAND gates ND 5  to ND 10  are input to the NAND gate ND 16 . The NAND gate ND 16  generates the functional mode signal FM 2 . Since the other inverse logic signals remain at a high level while two of the transfer signals R 1  to R 4  are at a high level, one of the outputs of the NAND gates ND 5  to ND 10  goes to a low level, and the NAND gate ND 16  generates the activated functional mode signal FM 2  of a high level. 
   The NAND gate ND 11  receives R 1 , R 2 , R 3  and R 4 B. The NAND gate ND 12  receives R 1 , R 2 , R 3 B, and R 4 . The NAND gate ND 13  receives R 1 , R 2 B, R 3 , and R 4 . The NAND gate ND 14  receives R 1 B, R 2 , R 3 , and R 4 . The outputs of the NAND gates ND 11  to ND 14  are inputted to the NAND gate ND 17 . The NAND gate ND 17  generates the functional mode signal FM 3 . Since the other inverse logic signals remain at a high level while three of the transfer signals R 1  to R 4  are at a high level, one of the outputs of the NAND gates ND 11  to ND 14  goes to a low level, and the NAND gate ND 17  generates the activated functional mode signal FM 3  of a high level. 
   Referring to the waveform diagram shown in  FIG. 6 , the functional mode signal FM 1  generated by the decoder  40  is activated every four cycles of clock signal CLK when one of the transfer signals R 1  to R 4  is at a high level. The functional mode signal FM 2  is activated every four cycles of clock signal CLK when two of the transfer signals R 1  to R 4  are at a high level. The functional mode signal FM 3  is activated every four cycles of clock signal CLK when three of the transfer signals R 1  to R 4  are at a high level. 
   According to an embodiment of the present invention, the functional mode setting circuit shown in  FIG. 7  uses a method in which each of reference voltages VR 1  to VRn (e.g., refer to  FIG. 8 ) set between the minimum high level voltage VIH, less than VDD, and the maximum low level voltage VIL, greater than GND, are compared with the signal S 1  input from a pin  10  and coding signals are generated. Here, the input signal S 1  is a DC signal that has a constant voltage level. Referring to  FIG. 7 , the input signal S 1  is simultaneously input to non-inverting input terminals (+) of differential amplifiers DF 1  to DFn and compared with reference voltages VR 1  to VRn. The differential amplifiers DF 1  to DFn amplify the voltage difference between the corresponding reference voltage and input signal S 1  and output the amplified signals D 1  to Dn. The differential signals D 1  to Dn are input to the decoder  50 . The decoder  50  has a combination logic as shown in FIG.  6  and generates one or more functional mode signals FMi from the input differential signals D 1  to Dn. 
   It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. 
   As described above, mode setting DC pin installed in the conventional integrated circuit is used to set the functions for tests in a packaging stage. Accordingly, designers can set their desired functions without a separate available pin for setting functions.