Abstract:
A receiver circuit is capable of improving its operating characteristics. The receiver circuit includes a variable converter configured to output off-set control voltages in a first output range in a first operation mode and output the off-set control voltages in a second output range in a second operation mode according to a test mode activation signal, and a sense amplifier configured to sense input data based on a sensitivity, wherein the sensitivity is controlled by the off-set control voltages.

Description:
CROSS-REFERENCES TO RELATED APPLICATION 
     The present application claims priority under 35 U.S.C. §119(a) to Korean application number 10-2007-0128299, filed on Dec. 11, 2007, which is incorporated herein by reference in its entirety as if set forth in full. 
     BACKGROUND 
     1. Technical Field 
     The embodiments described herein relate to a semiconductor integrated circuit and, more particularly, to a receiver circuit of a semiconductor integrated circuit. 
     2. Related Art 
     Generally, an input receiver is employed as an interface circuit in a conventional semiconductor device such as a semiconductor memory. The input receiver plays an important role in signal transmission to receive and buffer an input signal from an external circuit and to transfer the input signal internally. Operational parameters such as the voltage level and set-up/hold time for the input receiver are critical factors to determine high-speed response characteristics of the input receiver and ultimately the device. 
       FIG. 1  is a block diagram illustrating a conventional receiver circuit. Referring to  FIG. 1 , the conventional receiver circuit includes a first digital-to-analog converter  1 , a second digital-to-analog converter  2 , a sense amplifier  4 , and a latch unit  5 . 
     The first digital-to-analog converter  1  receives a first control signal ‘CNT1&lt;0:N&gt;’ and then outputs eye monitoring voltages EMC+ and EMC−. The second digital-to-analog converter  2  outputs off-set control voltages OCC+ and OCC− in response to a second control signal ‘CNT2&lt;0:N&gt;’. 
     The sense amplifier  4  senses and amplifies input data ‘DATA+’ and ‘DATA−’ according to a clock signal ‘CLK’. The latch unit  5  latches output signals ‘SA_OUT’ and ‘SA_OUTB’ of the sense amplifier  4  to output a receiving data signal ‘RXDATA’. 
     The operation of the receiver circuit of  FIG. 1  will now be discussed in detail. First, during an eye monitoring test, the first digital-to-analog converter  1  is driven and the eye monitoring voltages EMC+ and EMC− are output. The sense amplifier  4  senses and amplifies the input data ‘DATA+’ and ‘DATA−’ according to an off-set voltage that is controlled by the eye monitoring voltages EMC+ and EMC−. 
     When not in an eye monitoring test mode, the second digital-to-analog converter  2  is driven and the off-set control voltages OCC+ and OCC− are output. The sense amplifier  4  senses and amplifies the input data ‘DATA+’ and ‘DATA−’ according to an off-set voltage that is controlled by the off-set control voltages OCC+ and OCC−. 
     For example, if the eye monitoring voltages EMC+ and EMC− are in a range of a few hundreds of mV, the off-set control voltages OCC+ and OCC− are in a range of a few tens of mV. 
     The eye monitoring test is used for verifying that data transmitted from a transmission side, the transmitter, are correctly received by a receiving side, the receiver circuit. The accuracy of the data transmission can be verified by monitoring the result of overlay parts of the data outputs, i.e., by monitoring the data eye, through the eye monitoring test. The amount of jitter as well as the data eye can be verified through the eye monitoring test. 
     Because off-set voltages required in the sense amplifier  4  have different ranges depending on the mode of operation, the first and second digital-to-analog converters  1  and  2  are selectively driven according to the operating modes. 
       FIG. 2  is a circuit diagram illustrating the sense amplifier  4  included in the conventional receiver circuit of  FIG. 1 . Referring to  FIG. 2 , the sense amplifier  4  includes an input data amplifier  6 , a first off-set voltage adjust unit  8 , and a second off-set voltage adjust unit  7 . The input data amplifier  6  is made of a cross-coupled latch circuit. The input data amplifier  6  senses and amplifies the input data ‘DATA+’ and ‘DATA−’ according to the clock signal ‘clk’. The first off-set voltage adjust unit  8  receives the eye monitoring voltages EMC+ and EMC− from the first digital-to-analog converter  1  and then controls the off-set voltage of the input data amplifier  6 . The second off-set voltage adjust unit  7  receives the off-set control voltages OCC+ and OCC− from the second digital-to-analog converter  2  and then controls the off-set voltage of the input data amplifier  6 . 
     the sense amplifier  4  can suffer, however, from nonlinear characteristics because of a mismatch (for example, size or area) between an input transistor and the differential drain current and input voltage applied thereto. Accordingly, in order to avoid this problem, the number of transistors is increased in the first off-set voltage adjust unit  8  and the second off-set voltage adjust unit  7  in the sense amplifier, which increases the resource overhead, and as a result, the clock loading is more severe because of increased signal routing due to the additional transistors. 
     As described above, the conventional receiver circuit uses two or more digital-to-analog converters, such as the first and second digital-to-analog converters  1  and  2 , to output the off-set voltages in different ranges. Further, the sense amplifier  4  includes the first off-set voltage adjust unit  8 , which receives the output signals of the first digital-to-analog converter  1 , and the second off-set voltage adjust unit  7 , which receives the output signals of the second digital-to-analog converter  2 . 
     Accordingly, the sense amplifier  4  increases the resources required, and therefore the overhead and circuit area, of the conventional receiver circuit. 
     SUMMARY 
     A receiver circuit capable of improving its operating characteristics is described herein. 
     In one aspect, a receiver circuit comprises a variable converter configured to output off-set control voltages in a first output range in a first operation mode and to output the off-set control voltages in a second output range in a second operation mode according to a test mode activation signal, and a sense amplifier configured to sense input data, wherein the sense amplifier is controlled by the off-set control voltages. 
     The receiver circuit according to one embodiment can improve the operating characteristics by reducing the overhead of a sense amplifier and stably securing the set-up/hole margin. 
     These and other features, aspects, and embodiments are described below in the section “Detailed Description.” 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features, aspects, and embodiments are described in conjunction with the attached drawings, in which: 
         FIG. 1  is a block diagram illustrating a conventional receiver circuit; 
         FIG. 2  is a circuit diagram illustrating a sense amplifier included in the conventional receiver circuit of  FIG. 1 ; 
         FIG. 3  is a block diagram illustrating a receiver circuit according to one embodiment; 
         FIG. 4  is a detailed block diagram illustrating a variable converter included in the receiver circuit of  FIG. 3  according to one embodiment; 
         FIG. 5  is a detailed circuit diagram illustrating an N th  conversion cell of  FIG. 4  according to one embodiment; and 
         FIG. 6  is a detailed circuit diagram illustrating a sense amplifier included in the receiver circuit of  FIG. 3  according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 3  is a block diagram illustrating a receiver circuit  11  according to one embodiment. Referring to  FIG. 3 , the receiver circuit  11  can include a variable converter  10 , a sense amplifier  21 , and a latch unit  22 . 
     The variable converter  10  can be configured to output off-set control voltages ADC+ and ADC− in a first output range associated with a first operation mode according to a test mode activation signal ‘Enable’. Also, the variable converter  10  can be configured to output the off-set control voltages ADC+ and ADC− in a second output range associated with a second operation mode according to the test mode activation signal ‘Enable’. 
     The first operation mode can be indicative of an eye monitoring test mode and the second operation mode can be indicative of different operation modes other than the eye monitoring test mode. For example, the second operation mode can be an off-set control mode. If the off-set control voltages ADC+ and ADC− are in a range of a few hundreds of mV at the time of the eye monitoring test mode, the off-set control voltages ADC+ and ADC− can, e.g., be in a range of a few tens of mV at the time of the off-set control operation mode. 
     As described above, the eye monitoring test can be used for verifying that data transmitted from a transmission side, the transmitter, are correctly received by a receiving side, the receiver circuit  11 . The accuracy of the data transmission can be verified by monitoring the result of overlay parts of the data outputs, i.e., by monitoring the size of data eye, through the eye monitoring test. 
     The variable converter  10  can be configured to output the off-set control voltages ADC+ and ADC− in a relatively wide range at the time of the eye monitoring test and to output the off-set control voltages ADC+ and ADC− in a relatively narrow range at the time of the off-set control operation mode. 
     Thus, according to one embodiment, circuits for generating the off-set voltages can be simplified in such a manner that the variable converter  10  can be configured to generate the off-set voltages in different ranges according to the first and second operation modes. 
     The sense amplifier  21  can be configured to sense and amplify input data ‘DATA+ and ‘DATA−’ using off-set voltages controlled by the off-set control voltages ADC+ and ADC−. As compared with the sense amplifier  4  of the conventional receiver circuit, the sense amplifier  21  can be require less overhead, which is an issue in the sense amplifier  4  of the conventional receiver circuit, because the number of input transistors (or steering) can be reduced 
     Typically, the input data ‘DATA+’ and ‘DATA−’ are signals that are sent from a transmitter and received through a channel. 
     The latch unit  22  can be configured to latch and output the output signals of the sense amplifier  21 . The latch unit  22  can be implemented as a conventional latch circuit such as is widely used in typical receiver circuits. 
       FIG. 4  is a detailed block diagram illustrating the variable converter  10  included in the receiver circuit of  FIG. 3  according to one embodiment. Referring to  FIG. 4 , the variable converter  10  can include a control unit  11  and a conversion unit  12 . 
     The control unit  11  can be enabled in response to the test mode activation signal ‘Enable’ and can be configured to receive digital codes ‘CODE&lt;0:N−1&gt;’, thereby outputting first to N th  control signals ‘CNT&lt;0:N−1&gt;’ (N: integer more than 2). That is, when the test mode activation signal ‘Enable’ is activated, all bits of the control signals ‘CNT&lt;0:N−1&gt;’ can be activated and, when the test mode activation signal ‘Enable’ is deactivated, some bits of the control signals ‘CNT&lt;0:N−1&gt;’ can be activated. For example, when the test mode activation signal ‘Enable’ is deactivated, the control signals ‘CNT&lt;0:M−1&gt;’, which correspond to the lower bits of the control signals ‘CNT&lt;0:N−1&gt;’, can be activated and the control signals ‘CNT&lt;M:N−1&gt;’, which correspond to the upper bits of the control signals ‘CNT&lt;0:N−1&gt;’, can be deactivated. 
     When the test mode activation signal ‘Enable’ is activated, the control unit  11  can be configured to activate both a first bias voltage (a first voltage control signal ‘bias1’) and a second bias voltage (a second voltage control signal ‘bias2’) and, when the test mode activation signal ‘Enable’ is deactivated, the control unit  11  can be configured to activate only the first voltage control signal ‘bias1’. 
     When the test mode activation signal ‘Enable’ is activated, current paths formed in the conversion unit  12  can be increased according to the first and second voltage control signals ‘bias1’ and ‘bias2’. Therefore, as compared with the instance where only the first voltage control signal ‘bias1’ is activated, this instance provides a higher level of the off-set control voltages ADC+ and ADC−. 
     The conversion unit  12  can be driven in response to the control signals ‘CNT&lt;0:N−1&gt;’ and then can be configured to produce the off-set control voltages ADC+ and ADC−. In the conversion unit  12 , the more the activated bits of the control signals ‘CNT&lt;0:N−1&gt;’ are increased, the higher the off-set control voltages ADC+ and ADC− can be. 
     The conversion unit  12  can include first to N th  conversion cells  14 - 1  to  14 -N and a resistance unit  13 . 
     The first to N th  conversion cells  14 - 1  to  14 -N can be configured to receive the N-bit control signals ‘CNT&lt;0:N−1&gt;’ based on a bit-by-bit basis and the first to N th  conversion cells  14 - 1  to  14 -N can be configured to control the voltage levels of the off-set control voltages ADC+ and ADC− by commonly receiving the first and second voltage control signals ‘bias1’ and ‘bias2’. For example, the first conversion cell  14 - 1  can be configured to receive the first control signal ‘CNT&lt;0&gt;’, a first control bar signal ‘CNTB&lt;0&gt;’, which is complementary to the first control signal ‘CNT&lt;0&gt;’, and the first and second voltage control signals ‘bias1’ and ‘bias2’, and then to control the off-set control voltages ADC+ and ADC−. 
     The resistance unit  13  can include resistors R 1  and R 2 , which are connected between the first to N th  conversion cells  14 - 1  to  14 -N and a power supply voltage VDD, respectively. The off-set control voltages ADC+ and ADC− can be sent from connection nodes Node_ 1  and Node_ 2  between the first to N th  conversion cells  14 - 1  to  14 -N and the resistors R 1  and R 2 , respectively. 
       FIG. 5  is a detailed circuit diagram illustrating an Nth conversion cell  14 -N of  FIG. 4  according to one embodiment. Referring to  FIG. 5 , the N th  conversion cell  14 -N can include a first current path  15 -N, a second current path  16 -N, and a control signal input unit  17 -N. 
     The control signal input unit  17 -N can include a first NMOS transistor N 1  and a second NMOS transistor N 2 . The first NMOS transistor N 1  can have a gate to which the N th  control signal ‘CNT’&lt;N−1&gt; is applied, a source that is connected to the first and second current paths  15 -N and  16 -N, and a drain that is connected to the resistance unit  13 . The second NMOS transistor N 2  can have a gate to which an N th  control bar signal ‘CNTB’&lt;N−1&gt;, which is complementary to the N th  control signal ‘CNT’&lt;N−1&gt;, is applied, a source that is connected to the first and second current paths  15 -N and  16 -N, and a drain that is connected to the resistance unit  13 . 
     The first current path  15 -N can be configured to form the current path in the N th  conversion cell  14 -N in response to the first voltage control signal ‘bias1’. The first current path  15 -N can be made up of a third NMOS transistor N 3  configured to have a gate to which the first voltage control signal ‘bias1’ can be applied. 
     The second current path  16 -N also can be configured to form the current path in the N th  conversion cell  14 -N in response to the second voltage control signal ‘bias2’. The second current path  16 -N can be made up of a fourth NMOS transistor N 4  configured to have a gate to which the second voltage control signal ‘bias2’ can be applied. 
       FIG. 6  is a detailed circuit diagram illustrating a sense amplifier included in the receiver circuit of  FIG. 3  according to one embodiment. Referring to  FIG. 1 , the sense amplifier  21  can include an input data amplifying unit  23  and an off-set voltage adjust unit  24 . 
     The input data amplifying unit  23  can have the same configuration as the input data amplifier  6  of  FIG. 6 . The off-set voltage adjust unit  24  can be configured to control the off-set voltage of the input data amplifying unit  23  according to the off-set control voltages ADC+ and ADC−. 
     The operation of the sense amplifier  21  will be described in detail. When clock signal ‘clk’ is inactivated, the first NMOS transistor N 1  can be turned off and the current path can be blocked so that the sense amplifier  21  is not driven. At the same time, the first and second PMOS transistors P 1  and P 2  and a fifth PMOS transistor P 5  can be turned on, thereby precharging the output signals ‘SA_OUT’ and ‘SA_OUTB’ to a voltage level of the power supply voltage VDD. 
     Meanwhile, when a power-up signal ‘pwdnb’ is activated and the clock signal ‘clk’ is activated, the first and second PMOS transistors P 1  and P 2  and the fifth PMOS transistor P 5  can be turned off, and the first and second NMOS transistors N 1  and N 2  can be turned on. Accordingly, the sense amplifier  21  can be configured to execute the amplification of the input data DATA+ and DATA−. 
     The operation of the receiver circuit according to one embodiment will be described in detail. First, in the case of the eye monitoring test, the test mode activation signal ‘Enable’ can be activated. Based on the activation of the test mode activation signal ‘Enable’, all the bits of the first to N th  control signals ‘CNT’&lt;0:N−1&gt; can be activated and the first and second voltage control signals ‘bias1’ and ‘bias2’, which are sent from the control unit  11  in the variable converter  10 , can also be activated. 
     Because all the first and second voltage control signals ‘bias1’ and ‘bias2’ are activated, all the current paths of the first to N th  conversion cells  14 - 1  to  14 -N, i.e., the first and second current paths  15 -N and  16 -N, can be open. 
     All the bits of the first to N th  control signals ‘CNT’&lt;0:N−1&gt; can be activated, the entire first to N th  conversion cells  14 - 1  to  14 -N can be configured to operate. 
     Because all the first to N th  conversion cells  14 - 1  to  14 -N can be configured to operate with the opening of the current paths, the amount of current can be maximized and the off-set control voltages ADC+ and ADC− can be finally sent with a maximum value. 
     The eye monitoring test can be performed by adjusting the off-set voltage of the sense amplifier  21  to a maximum value, which is over the range in a normal operation, according to the off-set control voltages ADC+ and ADC− sent with the maximum value, and then by adjusting the sensitivity of the sense amplifier  21  with a maximum range. 
     On the other hand, in the case of the off-set control mode, the test mode activation signal ‘Enable’ can be inactivated. Accordingly, some bits of the first to N th  control signals ‘CNT’&lt;0:N−1&gt;, which are sent from the variable converter  10 , can be activated and only the first voltage control signal ‘bias1’ of the first and second voltage control signals ‘bias1’ and ‘bias2’ can be activated. 
     According to the activation of the first voltage control signal ‘bias1’, only the first current path  15 -N can be open in each of the first to N th  conversion cell  14 - 1  to  14 -N. 
     Because some bits of the first to N th  control signals ‘CNT’&lt;0:N−1&gt; are activated, some of the first to N th  conversion cell  14 - 1  to  14 -N can be configured to operate. 
     Some of the first to N th  conversion cell  14 - 1  to  14 -N, in which only one current path is open, can be configured to operate so that the amount of current of the conversion unit  12  in the off-set control mode can be less than that in the eye monitoring test mode and the off-set control voltages ADC+ and ADC− can also be lowered. 
     According to the off-set control voltages ADC+ and ADC−, which is lowered as compared with that in the eye test monitoring test mode, the off-set control mode can be performed by adjusting the off-set voltage of the sense amplifier  21  to a range in a normal operation and then by adjusting the sensitivity of the sense amplifier  21  based on the range. 
     The receiver circuit according to one embodiment can be employed in different fields such CPUs and ASICs. Furthermore, various embodiments are available to semiconductor integrated circuits that have three or more operation modes each of which requires a different off-set voltage range, as well as the first and second operation modes. 
     While certain embodiments have been described above, it will be understood that the embodiments described are by way of example only. Accordingly, the systems and methods described herein should not be limited based on the described embodiments. Rather, the systems and methods described herein should only be limited in light of the claims that follow when taken in conjunction with the above description and accompanying drawings.