Abstract:
A trimmer device for adjusting a reference signal of a target circuit is disclosed. The trimmer device includes: a switch controlling module and an impedance adjustment circuit. The switch controlling module includes: a fuse, selectively being melted according to the reference signal; and a control signal generating circuit, for generating a control signal according to the melting condition of the fuse. The impedance adjustment circuit includes: a switch module, being selectively conductive according to the control signal; and an impedance network, for determining an equivalent impedance of the impedance network according to the conducting condition of the switch module to further adjust the reference signal.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the invention 
         [0002]    The present invention relates to a trimmer device and a trimming method, and more particularly, to a trimmer device and a trimming method using switches to control an equivalent impedance value. 
         [0003]    2. Description of the Related Art 
         [0004]    Due to variances in fabrication, circuit characteristics such as resistance or capacitances may shift away from ideal values during the manufacture of integrated circuits. The above-mentioned variances in circuit characteristics may reduce the operation efficiency of circuits. In other cases, these variances may even cause malfunction during the circuits&#39; operation. 
         [0005]    However, during chip packaging, it is nearly impossible to adjust every chip device if time and cost are issues of concern. Please note that, for the perspective of an analog circuit, a primary goal is to maintain the value of reference signals residing in the integrated circuit (IC) in order that the values are equalized to the ideal values of the original circuit design. (For example, this is to maintain the voltage levels of specific nodes.) Therefore, a mechanism for performing the aforementioned adjusting operation is necessary for those skilled in the field of the art. 
         [0006]    Please refer to  FIG. 1 .  FIG. 1  is a diagram of a conventional trimmer device  100 . As shown in  FIG. 1 , the trimmer device  100  is utilized to adjust the reference voltage V F  of the target circuit  110 . The trimmer device  100  comprises three serial-connected resistors  120 ,  130 , and  140  and three fuses  150 ,  160 , and  170 . As shown in  FIG. 1 , the conducting conditions of the fuses  150 ,  160 , and  170  determine the equivalent impedance value of the resistors  120 ,  130 , and  140 . In other words, if the fuses  150 ,  160 , and  170  are not melted, each of the fuses  150 ,  160 , and  170  will act as a short circuit. During this time, corresponding resistances of the resistors  120 ,  130 , and  140  are ignored. 
         [0007]    On the other hand, if one of the fuses  150 ,  160 , and  170  is melted, one corresponding resistor among the resistors  120 ,  130 , and  140  will be conductive (i.e., the electric current can pass through the corresponding resistor), and a voltage can be generated across the corresponding resistor. Therefore, the voltage level of the reference voltage V F  can still be further adjusted. 
         [0008]    Furthermore, please refer to  FIG. 2 .  FIG. 2  is a diagram of another conventional trimmer device  200 . The trimmer device  200  is similar to the trimmer device  100 . The difference between them is that the resistors  220 ,  230 , and  240  and the fuses  250 ,  260 , and  270  are connected in series respectively. The operation and function of the trimmer device  200  is similar to that of the trimmer device  100 . The trimmer device  200  also manipulates the equivalent impedance of the resistors  220 ,  230 , and  240  by using the conducting condition such that the voltage level of the reference voltage V F  can be adjusted. 
         [0009]    Through the above-mentioned mechanism, during chip packaging, the manufacturer can utilize an external testing device (not shown) to detect the reference voltage. Additionally, the testing device can detect other reference signals. For example, the testing device can input a testing voltage and then detect a testing current corresponding to the testing voltage. The testing device can select some of the fuses  150 ,  160 , and  170 , which are to be melted, according to the variance of the reference voltage. In this way, the equivalent impedance provided by the resistors  120 ,  130 , and  140  can be adjusted such that the reference voltage is also adjusted to the ideal value of the original circuit design. 
         [0010]    Unfortunately, the above-mentioned trimmer devices  100  and  200  have some disadvantages. First, sometimes the fuses are not melted completely. So these fuses, which are not melted completely, have resistances. In this way, the resistance provided by the partially melted fuses may correspondingly influence the voltage level of the reference voltage V F . This situation prevents the original trimmer device from operating correctly. In addition, in the above-mentioned trimming mechanism, the equivalent impedance provided by the resistors can only be adjusted upward. Therefore, if the resistance of the target circuit is larger than the ideal value, the above-mentioned trimmer device is not capable of improving the situation. At this time, in order to raise the yield of the chip, the resistance of the target circuit has to be assigned a lower value when the chip is designed, where the lower value is lower than the ideal value. In this way, during chip packaging, the trimmer device is utilized to adjust the resistance upward to the ideal value. However, the above-mentioned trimming mechanism makes the adjustment of all chips necessary. Therefore, although the yield can be increased, a lot of time and costs are required using this method. 
       SUMMARY OF THE INVENTION 
       [0011]    In view of the above-mentioned problems, an object of the claimed invention is to provide a trimmer device and related trimming method. 
         [0012]    According to an embodiment of the claimed invention, a trimmer device for adjusting a reference signal of a target circuit is disclosed. The trimmer device comprises: a switch controlling module, and an impedance adjusting circuit. The switch controller includes: a fuse, selectively melted according to an ideal value of the reference signal; and a control signal generating circuit, for generating a control signal according to a conducting condition of the fuse. The impedance adjusting circuit comprises: a switch module, for selectively conductive according to the control signal; and an impedance network, for determining an equivalent impedance of the impedance network according to a conducting condition of the switch module such that the reference signal is adjusted. 
         [0013]    According to another embodiment of the claimed invention, a trimming method for adjusting a reference signal of a target circuit is disclosed. The trimming method utilizes a switch control module, the switch control module comprises: a fuse and a control signal generating circuit, and the trimming method includes: determining a conducting condition of the fuse according to the reference signal by using the control signal generating circuit for generating a control signal; and controlling an equivalent impedance of an impedance network, according to the control signal such that the reference signal is adjusted. 
         [0014]    The claimed invention trimmer device can control the reference signal or the equivalent impedance of the entire circuit by controlling switches. In contrast to the prior art control mechanism utilizing fuses, the claimed invention trimmer device is more flexible, and allows the reference signal or the equivalent impedance to be adjusted upward and downward. Therefore, the chip is designed in the typical way without purposely reducing the impedance of the target circuit to meet the demand of yield. In this way, when the chip is being packaged, the claimed invention trimmer device only has to adjust the target circuit, which has an incorrect impedance value (i.e., reference signal). Therefore, the claimed invention can reduce packaging costs and time. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a diagram of a conventional trimmer device. 
           [0016]      FIG. 2  is a diagram of a second conventional trimmer device. 
           [0017]      FIG. 3  is diagram of a trimmer device according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    Please refer to  FIG. 3 , which is diagram of a trimmer device  300  according to the present invention. As shown in  FIG. 3 , trimmer device  300  comprises an impedance adjusting circuit  310  and a switch controlling module  320 . The impedance adjusting circuit  310  comprises a plurality of resistors  311  and  312  and a plurality of transistors  313  and  314 . The electronic connections among the above-mentioned devices are shown in  FIG. 3 , and thus omitted herein for the sake of brevity. Please note that, in this embodiment of the present invention, the transistors  313  and  314  are utilized as switches. 
         [0019]    The switch controlling module  320  is utilized to control the switches  313  and  314  (i.e., to control the conducting conditions of the switches  313  and  314 ) to adjust the equivalent resistance of the resistors  311  and  312  such that the reference signal V F  can be further adjusted. It is noted that, because the present invention trimmer device  300  utilizes the characteristics of the switches to control the equivalent impedance of the resistors  311  and  312 , the trimmer device  300  can achieve comparatively better design flexibilities. For example, as long as the initial conducting conditions of the switches  313  and  314  are appropriately predetermined, the equivalent impedance of the trimmer device  300  can be adjusted upward (i.e., the equivalent impedance increases), and also adjusted downward (i.e., the equivalent impedance decreases). In other words, the voltage level V F  of the reference signal V F  can be adjusted upward or downward. Therefore, in this embodiment of the present invention, the initial conducting condition of the switch  313  is on, and the initial conducting condition of the switch  314  is off. In this way, if the resistance of target circuit  301  is less than an ideal value, the switch controlling module  320  can turn off the switch  313 . In this way, the equivalent impedance becomes a larger value R 1 +R 2 . On the other hand, if the resistance of the target circuit  301  is greater than the ideal value, the switch controlling module  320  can turn on the switch  314  such that the equivalent impedance becomes a smaller resistance 0. 
         [0020]    Please note that, in this embodiment, the initial conducting conditions of the switches  313  and  314  are provided as an illustration for the embodiment, and are not a limitation of the present invention. In the actual implementation, the circuit designer can assign the initial conducting conditions of the switches  313  and  314  according to the requirements at hand. For example, the switches  313  and  314  can both be on initially. This change also obeys the spirit of the present invention. 
         [0021]    In order to achieve the above-mentioned mechanism, the switch controlling module  320  comprises two switch controlling units  350  and  360 , which are respectively coupled to the switches  313  and  314 , for controlling (i.e., switching) the switches  313  and  314 . 
         [0022]    Please refer to  FIG. 3  again. The switch controlling unit  350  comprises a fuse  351  and a control signal generating circuit  352 . The control signal generating circuit  352  comprises a resistor  353  and an inverter  354 . As shown in  FIG. 3 , the fuse  351  is coupled between the node A and the ground voltage, the resistor  353  is coupled between the node A and a high voltage level, the input end of the inverter  354  is coupled to the node A, and the output node of the inverter  354  is coupled to the switch  313  (i.e., the gate of the transistor  313 ). 
         [0023]    In this embodiment of the present invention, when the trimmer device  300  is in the initial condition, the fuse  351  has not yet melted. At this time, the voltage level of the node A corresponds to the ground level (i.e., logic 0). Next, after the inverter  354  performs the inverting operation, the control signal generating circuit  352  provides a high voltage level (i.e., logic 1) to the gate of the transistor  313  such that the transistor  313  is turned on. 
         [0024]    On the other hand, the switch controlling unit  360  is similar to the switch controlling unit  350 . The switch controlling unit  360  comprises a fuse  361  and a control signal generating circuit  362 . The control signal generating circuit  362  comprises a resistor  363  and an inverter  364 . As shown in  FIG. 3 , the fuse  361  is coupled between the node B and a high voltage level, the resistor  363  is coupled between the node B and the ground voltage, and the input end of the inverter  354  is coupled to the node B, and the output end of the inverter  354  is coupled to the switch  314  (i.e., the gate of the transistor  314 ). 
         [0025]    In this embodiment of the present invention, when the trimmer device  300  is in the initial condition, the fuse  361  has not yet melted. At this time, the voltage level of the node B corresponds to the high voltage level (i.e., logic 1). Next, after the inverter  364  performs the inverting operation, the control signal generating circuit  362  provides a low voltage level (i.e., logic 0) to the gate of the transistor  314  such that the transistor  314  is turned off. 
         [0026]    Under the control of the switch controlling module  320 , as mentioned previously, in the initial condition, the equivalent impedance provided by the impedance adjusting circuit  310  is equal to the resistance R 1 , which is provided by the resistor  312 . 
         [0027]    During chip packaging, an external testing device (not shown in  FIG. 3 ) can detect whether the reference voltage V F  or other reference signals comply with the ideal values. For example, the testing device can input a testing voltage and then measure a corresponding current such that the impedance of the target circuit  301  can be calculated. If the reference voltage V F  is lower than an ideal value (i.e., the impedance of the target circuit  301  is lower than an ideal value), the testing device can melt the fuse  351  of the switch controlling unit  350 . In this way, the voltage level of the node A corresponds to a high voltage level, and the gate of the transistor  313  corresponds to a ground voltage. Therefore, the switch  313  is turned off. This makes the equivalent impedance become a higher value R 1 +R 2 , and the reference voltage V F  is thereby increased. 
         [0028]    On the other hand, if the reference voltage V F  is higher than an ideal value (i.e., the resistance of the target circuit  301  is greater than an ideal value); the testing device can melt the fuse  361  of the switch controlling unit  360 . In this way, the voltage level of the node B corresponds to a ground voltage, and the gate of the transistor  314  corresponds to a high voltage level. Therefore, the switch  314  is turned on. This makes the equivalent impedance become a lower value 0, and the reference voltage V F  is thereby reduced. 
         [0029]    Please note that, the above-mentioned circuit configuration illustrates an embodiment of the present invention and is not a limitation of the present invention. For example, in order to adjust the resistance or the reference signals more precisely, the present invention trimmer device can comprise additional resistors and, corresponding to the resistors, additional switch controlling units. Furthermore, the internal devices of the trimmer device can be coupled in different ways, for example, a more complex serial-parallel coupling. Those having average skill in the art readily understand that the trimmer device can be implemented with variant circuits, and the trimmer devices should all obey the spirit of the present invention. Taking the prior art trimmer devices  100  and  200  as examples, the present invention can exchange the fuses with switches and add switch controlling modules, capable of controlling the switches, into the trimmer device  100  and  200 . In this way, controlling the adjustment of the reference signal can also be achieved. This change also obeys the spirit of the present invention. 
         [0030]    Please note that, in the switch controlling units  350  and  360 , the inverters  354  and  364  are utilized to perform a level shifting operation. In other words, if the fuses  351  and  361  are not completely melted such that the voltage levels of the nodes A and B do not correspond to a “clean” high voltage level or ground level, the inverters  354  and  364  can invert the above-mentioned unclean voltage levels into cleaner voltage levels. This ensures that the switches  313  and  314  can be switched correctly. 
         [0031]    However, the inverters  354  and  364  can be optional devices. For example, if the fuses  351  and  361  can be melted normally (i.e., the voltage levels of the nodes A and B can correctly be pulled up or down after the fuses  351  and  361  are melted) or the voltage levels of the nodes A and B are sufficient to trigger the switching operation of the switches  313  and  314 , the inverters  354  and  364  are no longer needed. In other words, the switch controlling units  350  and  360  need only comprise the resistors  353  and  363  and the fuses  351  and  361 . This change also obeys the spirit of the present invention. 
         [0032]    In contrast to the prior art, the present invention trimmer device can control the reference signal or the equivalent impedance of the entire circuit through switching switches. Instead of the prior art control mechanism utilizing fuses, the present invention trimmer device is more flexible, and can allow the reference signal or the equivalent impedance to be adjusted upward and downward. Therefore, the chip can be designed without purposely reducing the impedance of the target circuit to meet the demand of yield. In this way, when the chip is being packaged, the present invention trimmer device need only adjust the target circuit, which has an incorrect impedance value (i.e., reference signal). Therefore, the present invention can reduce the packaging costs and time. 
         [0033]    While certain exemplary embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that this invention should not be limited to the specific construction and arrangement shown and described, since various other modifications may occur to those ordinarily skilled in the art.