Abstract:
Disclosed is a display driving device including a bonding resistance measurement circuit. The display driving device may include: first and second pads bonded to a pad of a display panel through a wire and configured to provide bonding resistance; and a bonding resistance measurement circuit configured to measure the bonding resistance by comparing an input voltage applied to the bonding resistance through the first pad to one or more preset reference voltages.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present disclosure relates to a display driving device, and more particularly, to a technique for measuring bonding resistance. 
         [0003]    2. Related Art 
         [0004]    In general, a display driving device is manufactured with an integrated circuit (IC), and the IC is mounted on a display panel. 
         [0005]    The mounting method may be divided into COG (Chip On Glass), TCP (Tape Carrier Package) and COF (Chi On Film). Among the mounting methods, the COG method has a simpler structure than the TCP method and the COF method. Thus, the COG method is widely used. 
         [0006]    According to the COG method, a display driving device is bonded on a display panel through a wire. At this time, since the bonding resistance of the wire may have an influence on power, the bonding resistance needs to be set as low as possible. 
         [0007]    Therefore, it is necessary to measure whether the IC is normally bonded or how much the bonding resistance is. 
         [0008]    According to the related art, an external measuring device is connected to a pad of a display panel, in order to measure bonding resistance. In this method, resistance from the display panel to the measuring device and an error of the measuring device are added. Thus, an accurate bonding resistance value cannot be acquired. 
         [0009]    Therefore, there is a demand for a technique for accurately measuring the magnitude of bonding resistance that has a large influence on the operating ability of the display driving device. 
       SUMMARY 
       [0010]    Various embodiments are directed to a display driving device including a bonding resistance measurement circuit capable of accurately measuring bonding resistance. 
         [0011]    Also, various embodiments are directed to a display driving device capable of checking whether bonding was normally conducted, through measured bonding resistance. 
         [0012]    In an embodiment, a display driving device may include: first and second pads bonded to a pad of a display panel, and configured to provide bonding resistance; and a bonding resistance measurement circuit configured to measure the bonding resistance by comparing an input voltage applied to the bonding resistance through the first pad to one or more preset reference voltages. 
         [0013]    In an embodiment, a display driving device may include: first and second pads bonded to a pad of a display panel, and configured to provide bonding resistance; a first resistor configured to transmit an input voltage dropping a supply voltage to the first pad; a reference voltage generation unit configured to generate a first reference voltage and a second reference voltage from the supply voltage, the second reference voltage being larger than the first reference voltage; and a bonding resistance determination unit configured to determine the range of the bonding resistance according to a magnitude relation between the input voltage and the first reference voltage and a magnitude relation between the input voltage and the second reference voltage. 
         [0014]    According to the present embodiments, since the bonding resistance measurement circuit is embedded in the display driving device, the bonding resistance between the display panel and the display driving device can be accurately measured. 
         [0015]    Furthermore, the display driving device having the bonding resistance measurement circuit embedded therein can be used to check whether bonding was normally conducted, through measured bonding resistance. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a block diagram illustrating a pad configuration of a display driving device including a bonding resistance measurement circuit according to an embodiment of the present invention. 
           [0017]      FIG. 2  is a circuit diagram of the bonding resistance measurement circuit according to the embodiment of the present invention. 
           [0018]      FIG. 3  is a flowchart for describing an operation of the bonding resistance measurement circuit of  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    Hereafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The terms used in the present specification and claims are not limited to typical dictionary definitions, but must be interpreted into meanings and concepts which coincide with the technical idea of the present invention. 
         [0020]    Embodiments described in the present specification and configurations illustrated in the drawings are preferred embodiments of the present invention, and do not represent the entire technical idea of the present invention. Thus, various equivalents and modifications capable of replacing the embodiments and configurations may be provided at the point of time that the present application is filed. 
         [0021]      FIG. 1  is a circuit diagram illustrating a pad configuration of a bonding resistance measurement circuit according to an embodiment of the present invention. 
         [0022]    Referring to  FIG. 1 , a display driving device  100  according to an embodiment of the present invention includes two pads  10  and  20  and a bonding resistance measurement circuit  60 . The two pads  10  and  20  are bonded to a pad  30  of a display panel  200  through wires  40  and  50 , and the bonding resistance measurement circuit  60  is installed in the display driving device  100  in order to measure bonding resistance. 
         [0023]    The bonding resistance measurement circuit  60  measures bonding resistance R 1 +R 2  from the pad  10  to the pad  20 . 
         [0024]    According to the present embodiment, a supply voltage POWER is applied to the pad  10  and a ground voltage GND is applied to the other pad  20 , in order to measure the bonding resistance. The supply voltage POWER may include VDD or VCC, and is applied to the pad  10  through a resistor. 
         [0025]    The bonding resistance measurement circuit  60  according to the present embodiment measures the range of the bonding resistance R 1 +R 2  using a voltage between the pad  10  and the pad  20 . The bonding resistance measurement circuit  60  has the following configuration. 
         [0026]      FIG. 2  is a circuit diagram of the bonding resistance measurement circuit according to the embodiment of the present invention. 
         [0027]    Referring to  FIG. 2 , the bonding resistance measurement circuit  60  according to the embodiment of the present invention includes a voltage dropping unit  11 , reference voltage generation units  12  and  13 , a comparison unit  14  and a buffer unit  15 . 
         [0028]    The voltage dropping unit  11  may include a resistor RS 1 , and transmit an input voltage VIN dropped from the supply voltage POWER to the first pad  10 . 
         [0029]    The reference voltage generation unit  12  includes resistors RS 2  and RS 3 . Furthermore, the reference voltage generation unit  12  includes a switch SW 1  configured to transmit a reference voltage VREF 1  to the comparison unit  14 , the reference voltage VREF 1  being divided from the supply voltage POWER by the resistors RS 1  and RS 3 . The resistors RS 2  and RS 3  are connected in series between the supply voltage POWER and the ground voltage GND, and the voltage divided by the resistors RS 2  and RS 3  is provided as the reference voltage VREF 1 . The switch SW 1  is turned on when bonding resistance measurement is started, and turned off when the input voltage VIN is larger than the reference voltage VREF 1 . 
         [0030]    The reference voltage generation unit  13  includes resistors RS 4  and RS 5 . Furthermore, the reference voltage generation unit  13  includes a switch SW 2  configured to transmit a reference voltage VREF 2  to the comparison unit  14 , the reference voltage VREF 2  being divided from the supply voltage POWER by the resistors RS 4  and RS 5 . The resistors RS 4  and RS 5  are connected in series between the supply voltage POWER and the ground voltage GND, and the voltage divided by the resistors RS 4  and RS 5  is provided as the reference voltage VREF 2 . The switch SW 2  is turned on when the input voltage VIN is larger than the reference voltage VREF 1 . 
         [0031]    In  FIG. 2 , the first resistor RS 1 , the second resistor RS 2  and the fourth resistor RS 4  have the same resistance value, and the third resistor RS 3  has a smaller resistance value than the fifth resistor RS 5 . 
         [0032]    The comparison unit  14  compares the input voltage VIN and the reference voltage VREF 1  when the switch SW 1  is turned on, or compares the input voltage VIN and the reference voltage VREF 2  when the switch SW 2  is turned on, and outputs a comparison signal corresponding to the comparison result. The buffer unit  15  includes inverters, buffers the comparison signal, and then outputs an output voltage VOUT. 
         [0033]    The comparison unit  14  determines the range of the bonding resistance R 1 +R 2 , depending on which one of the input voltage VIN and the reference voltage VREF 1  is higher than the other voltage. The input voltage VIN is a voltage divided from the supply voltage POWER by the resistor RS 1  and the bonding resistance R 1 +R 2 , and the reference voltage VREF 1  is a voltage divided from the supply voltage POWER by the resistors RS 2  and RS 3 . 
         [0034]    Furthermore, the comparison unit  14  determines the range of the bonding resistance R 1 +R 2 , depending on which one of the input voltage VIN and the reference voltage VREF 2  is lower than the other voltage. The reference voltage VREF 2  is a voltage divided from the supply voltage POWER by the resistors RS 4  and RS 5 . 
         [0035]    For example, the comparison unit  14  according to the present embodiment determines that the range of the bonding resistance R 1 +R 2  is between zero and the resistance of the resistor RS 3  when the input voltage VIN is smaller than the reference voltage VREF 1 , determines that the range of the bonding resistance R 1 +R 2  is between the resistance of the resistor RS 3  and the resistance of the resistor RS 5  when the input voltage VIN is larger than the reference voltage VREF 1  and smaller than the reference voltage VREF 2 , and determines that the range of the bonding resistance R 1 +R 2  is larger than the resistance of the resistor RS 5  when the input voltage VIN is larger than the reference voltage VREF 2 . 
         [0036]    As such, the comparison unit  14  serves as a bonding resistance determination unit which determines the range of the bonding resistance according to the magnitude relation between the input voltage VIN and the reference voltage VREF 1  or between the input voltage VIN and the reference voltage VREF 2 . The resistors RS 3  and RS 5  are internal passive resistance elements for one-to-one comparison to the bonding resistance R 1 +R 2 , and the resistors RS 1 , RS 2  and RS 4  are passive resistance elements which are operated in the voltage input range of the comparison unit  14 . 
         [0037]    The switches SW 1  and SW 2  are controlled by a controller (not illustrated). When the bonding resistance measurement is started, the controller turns on the switch SW 1  to transmit the reference voltage VREF 1  to the comparison unit  14 . When a comparison result of the comparison unit  14  indicates that the input voltage VIN is larger than the reference voltage VREF 1 , the controller turns on the switch SW 2  to transmit the reference voltage VREF 2  to the comparison unit  14 . At this time, when the switch SW 1  is turned on, the switch SW 2  is turned off, and when the switch SW 2  is turned on, the switch SW 1  is turned off. 
         [0038]      FIG. 3  is a flowchart for describing the operation of the bonding resistance measurement circuit of  FIG. 2 . 
         [0039]    Referring to  FIG. 3 , when bonding resistance measurement is started, the bonding resistance measurement circuit  60  turns on the switch SW 1  and turns off the switch SW 2 , at step S 10 . 
         [0040]    The bonding resistance measurement circuit  60  compares the input voltage VIN to the reference voltage VREF 1  transmitted through the switch SW 1  at step S 20 . 
         [0041]    When the input voltage VIN is smaller than the reference voltage VREF 1 , the bonding resistance measurement circuit  60  determines that the bonding resistance R 1 +R 2  is smaller than the resistance value of the resistor RS 3 , at step S 30 . 
         [0042]    On the other hand, when the input voltage VIN is larger than the reference voltage VREF 1 , the bonding resistance measurement circuit  60  determines that the bonding resistance R 1 +R 2  is larger than the resistance value of the resistor RS 3 , at step S 40 . Then, the bonding resistance measurement circuit  60  turns off the switch SW 1  and turns on the switch SW 2 , at step S 50 . 
         [0043]    Then, the bonding resistance measurement circuit  60  compares the input voltage VIN to the reference voltage VREF 2  transmitted through the switch SW 2  at step S 60 . 
         [0044]    When the input voltage VIN is smaller than the reference voltage VREF 2 , the bonding resistance measurement circuit  60  determines that the bonding resistance R 1 +R 2  is larger than the resistance value of the resistor RS 3  and smaller than the resistance value of the resistor RS 5 , at step S 70 . 
         [0045]    When the input voltage VIN is larger than the reference voltage VREF 2 , the bonding resistance measurement circuit  60  determines that the bonding resistance R 1 +R 2  is larger than the resistance value of the resistor RS 5 , at step S 80 . 
         [0046]    As such, the bonding resistance measurement circuit  60  determines that the range of the bonding resistance R 1 +R 2  is between zero and the resistance of the resistor RS 3  when the input voltage VIN is smaller than the reference voltage VREF 1 , determines that the range of the bonding resistance R 1 +R 2  is between the resistance of the resistor RS 3  and the resistance of the resistor RS 5  when the input voltage VIN is larger than the reference voltage VREF 1  and smaller than the reference voltage VREF 2 , and determines that the range of the bonding resistance R 1 +R 2  is larger than the resistance of the resistor RS 5  when the input voltage VIN is larger than the reference voltage VREF 2 . 
         [0047]    If the design area and switch signals are allowed, switches may be added to more precisely determine the magnitude of the bonding resistance. 
         [0048]    In the COG technology, the bonding resistance of a wire has a large influence on the operating ability of the chip. Thus, it is very important to determine the magnitude of the bonding resistance. For example, when the bonding was normally conducted, the wire has a bonding resistance of several ohms to tens of ohms (Q). However, when the bonding was not normally conducted, the wire may have a bonding resistance of several hundreds of ohms to several kill-ohms (Q). 
         [0049]    Since the bonding resistance measurement circuit according to the present embodiment can determine the magnitude range of the bonding resistance, the bonding resistance measurement circuit can be utilized as a circuit capable of checking whether the display driving device  100  was normally bonded to the display panel  200 . 
         [0050]    While various embodiments have been described above, it will be understood to those skilled in the art that the embodiments described are by way of example only. Accordingly, the disclosure described herein should not be limited based on the described embodiments.