JP3970778B2 - Organic EL drive circuit and organic EL display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an organic EL drive circuit and an organic EL display device, and more specifically, a current value corresponding to display data is generated by a D / A conversion circuit using a current mirror circuit, and an organic EL panel is connected via its terminal pins. The present invention relates to a structure of a circuit layout of an organic EL driving circuit capable of generating a driving current with high integration efficiency and high accuracy in a current driving circuit of a column line (anode side driving line, the same applies hereinafter).
[0002]
[Prior art]
In an organic EL display panel of an organic EL display device mounted on a mobile phone, a PHS, a DVD player, a PDA (mobile terminal device), etc., there are 396 (132 × 3) terminal pins (hereinafter referred to as pins) of column lines, A row line having 162 pins has been proposed, and the number of column line and row line pins tends to increase further.
The output stage of the current drive circuit of such an organic EL display panel is provided with a drive circuit for a current source, for example, an output circuit using a current mirror circuit, corresponding to the pin, regardless of whether it is an active matrix type or a simple matrix type.
[0003]
The output circuit by the current mirror circuit is arranged corresponding to the pin, and the drive stage thereof is, for example, as shown in Japanese Patent Application No. 2002-82662, a parallel drive current mirror circuit having a number of output side transistors corresponding to the pin. Then, a reference current is received from a reference current generation circuit as an input stage in front, and a mirror current is generated corresponding to the pin. Furthermore, a D / A conversion circuit composed of a current mirror is provided for each pin, and each D / A conversion circuit receives the mirror current as a reference drive current, and receives display data on the basis of this current. Then, D / A conversion is performed to generate a drive current corresponding to the pin, and the output circuit of the current mirror is driven.
Thus, by generating a drive current with a current mirror configuration, for example, in the case of a passive matrix, a large current of about mA or 1 A is amplified from a very small reference current of about several μA while suppressing power loss. Therefore, a driving circuit with low power consumption can be realized. In the case of an active matrix, a driving current of 1 nA to 10 μA can be obtained with low power consumption.
[0004]
For this reason, in the current drive circuit of the organic EL display panel, many unit transistors constituting the current mirror are arranged corresponding to the pads.
FIG. 3 is an explanatory diagram of the layout of the unit transistor 1 in the prior art, FIG. 3A is a transistor arrangement block, FIG. 3B is a plan view of the unit transistor constituting the current mirror, and FIG. (C) is a sectional view thereof.
As shown in FIG. 3C, the unit transistor 1 is element-isolated in a rectangular region by a buried layer (B / L) 11 and an element isolation region 12, and a base region 13b, an emitter region 13e, a collector region 13c, Is formed on the surface side of the substrate 16 in a rectangular shape. Reference numerals 14b, 14e, and 14c denote a base contact, an emitter contact, and a collector contact, respectively. The collector contact 14c is connected to the collector region 13c through the collector wall 15 and the buried layer 11.
Reference numeral 17 denotes an NSG interlayer separation film, and reference numeral 18 denotes an upper polysilicon insulating layer (P-SiN).
Then, as shown in FIG. 3A, two such unit transistors 1 are arranged in the arrangement direction of the pads 2 (lateral direction in the drawing) in the transistor arrangement block 3, and the direction perpendicular to the pad arrangement direction ( Many are provided in two rows in the vertical direction). Such transistor array blocks 3 arranged in two rows are repeatedly formed in the pad array direction, and the current drive circuit corresponding to the pins of the organic EL display panel is made into an IC.
[0005]
The transistor array block 3 in this two-row arrangement is determined from the fact that each pin of the organic EL display panel is arranged by repeating G, R, and B. Each pin is associated with this pin arrangement. This is because the pads 2 connected to are arranged.
For example, when the pad pitch is 50 μm, the element formation width is 44 μm, the horizontal interval is 6 μm, two transistors are formed in the element formation width of 44 μm at an interval of 50 μm, and each pin is driven. A large number of transistors necessary for the circuit are formed in the vertical direction.
As a result, the unit transistors 1 in the two-row arrangement coincide with the positions of the pads 2 corresponding to the respective output pins, and are, for example, about several tens to hundreds in length (the length is 1.0 mm to 3 mm). The transistor is arranged with a length of about 0.0 mm). Most of these transistors are current mirror connected in the upper wiring layer.
At this time, a current mirror output circuit (output stage current source) and a current switching D / A conversion circuit having a current mirror configuration are selected from a plurality of transistors in two rows at positions where the pair characteristics are aligned as much as possible.
[0006]
In FIG. 3A, there are two rows, but in order to improve the integration rate, three pins G, R, and B are set as one unit (corresponding to a pixel pitch in the column direction of G, R, and B). In some cases, a transistor arrangement block in which the unit transistors 1 are arranged in six rows is repeated. At this time, the width in the pin direction is 150 μm, but in this case, the drive circuit for current-driving each pin corresponding to each pad 2 in units of two rows is assigned in the vertical direction.
By the way, Patent Document 1 discloses a driving circuit for an organic EL element in which organic EL elements arranged in a matrix are driven by current and the anode and cathode of the organic EL element are reset to the ground. Further, Patent Document 2 discloses a technique for driving an organic EL element with low power consumption using a DC-DC converter.
[0007]
[Patent Document 1]
Japanese Patent Laid-Open No. 9-232974 [Patent Document 2]
Japanese Patent Laid-Open No. 2001-143867
[Problems to be solved by the invention]
In the current drive circuit of the organic EL, the drive stage and the output stage are provided for each pin of the organic EL panel, with the input stage being shared. The closer the output stage is to the pad connected to the pin, the smaller the loss. Therefore, the output stage is inevitably provided corresponding to the pad.
On the other hand, in order to reduce the number of chips of a drive IC (LSI) arranged on the organic EL panel, it is necessary to increase the number of output pins per chip. As a result, the pitch of the pads 2 becomes smaller, and the unit transistors constituting the current mirror circuit tend to become longer in the vertical direction (direction perpendicular to the pad arrangement direction) as shown in FIG. .
In such a configuration, when a large current of about mA or 1 A is generated from a very small reference current of about several μA, variations in the conversion accuracy of the D / A converter circuit cause variations in the output current of the output stage current source. There is a problem that it becomes uneven brightness.
In particular, in a current switching D / A conversion circuit having a current mirror configuration, a current amplified by weighting the reference current by 2 times, 4 times, 8 times, 16 times,... Is obtained in an output side transistor connected to the current mirror. Therefore, several tens to about 100 transistors connected to the current mirror are required. For this reason, it is important to ensure the pair characteristics of the transistors in the current mirror configuration with respect to the input side transistors. The pair characteristics are affected by the distance between the transistors and the position where the transistors are selected.
In order to make the characteristics as uniform as possible in the above number of transistors, it is preferable to select transistors at close positions. However, as shown in FIG. When the transistors are arranged vertically, the distance between the paired transistors is increased and it is difficult to ensure the pair characteristics of the input side transistor and the output side transistor. In addition, the wiring line for connecting the current mirror becomes longer and the resistance value becomes larger. As a result, the D / A conversion accuracy is lowered, and variations in accuracy occur in each D / A conversion circuit.
Moreover, since the vertical pattern to a pad corresponding is to be arranged at predetermined intervals, the occupied Mel ratio of parts of the between the pattern and the pattern is increased, it becomes wasted space The integration rate of the entire IC (LSI) is reduced.
An object of the present invention is to solve such problems of the prior art, and to provide an organic EL drive circuit and an organic EL display device that can output a drive current with high integration efficiency and high accuracy. There is.
[0009]
[Means for Solving the Problems]
The characteristics of the organic EL drive circuit and the organic EL display device of the present invention for achieving such an object are provided with a plurality of pads provided corresponding to the terminal pins and connected to the terminal pins, and provided corresponding to the pads. A current switching D / A conversion circuit having a current mirror configuration for receiving display data and generating an analog current for display corresponding thereto, and an output current from the D / A conversion circuit provided corresponding to the pad A plurality of current sources provided corresponding to R, G, and B that are driven and output drive current to the terminal pins through the pads, and 3n times the pad pitch in the pad arrangement direction (n is a positive integer) A rectangular transistor array block having a number of transistors having a width substantially corresponding to the pad array direction and having four or more transistors formed in relation to the width,
In the transistor arrangement block, the R / G / B D / A conversion circuits are arranged in a direction perpendicular to the pad arrangement direction, and the transistors constituting the current mirror circuit of the D / A conversion circuit are selected and the IC is selected. It is what has been made.
In addition, each of the plurality of current sources corresponding to R, G, and B has a current mirror circuit, and is assigned between the D / A conversion circuit and the pad in the transistor array block. Is selected.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Thus, according to the present invention, in a rectangular transistor arrangement block having a width of 3n times the pad pitch provided corresponding to the pin and in which four or more transistors are arranged in this width, R , G, and B are arranged in a direction perpendicular to the pad arrangement direction to form a current mirror circuit for each D / A that receives display data.
In this way, the D / A corresponding to the R, G, B pins is provided corresponding to the pad pitch width of 3n times without corresponding to each pad, and the R, G, B circuits are provided in the vertical direction. By laying out and making an IC, when a current mirror circuit is configured, the distance between transistors connected to the current mirror can be made shorter than in the past. As a result, the wiring line can be shortened, and a transistor with matched pair characteristics can be selected as the output side transistor of the current mirror circuit.
Further, the transistor arrangement block forming each R / G / B D / A, which requires a large number of unit transistors, is formed as a repetition of at least 3 pad pitches in the pad arrangement direction. The gap area between the blocks is reduced, and the unnecessary area can be reduced accordingly.
As a result, a highly accurate D / A conversion circuit can be obtained, and an organic EL drive circuit and an organic EL display device that can output a drive current with high integration efficiency and high accuracy can be easily realized.
[0011]
【Example】
FIG. 1 is an explanatory diagram of a layout of unit transistors constituting a D / A of a current driving circuit and a current mirror of an output stage current source of an embodiment to which the organic EL driving circuit of the present invention is applied, and FIG. It is explanatory drawing of the layout of the unit transistor which comprises D / A of the other Example and the current mirror of an output stage current source. In addition, the same component as FIG. 3 is shown with the same code | symbol.
In FIG. 1, reference numeral 10 denotes a layout of unit transistors constituting a D / A and a current mirror of an output stage current source provided in correspondence with pins in a column driver IC of an organic EL driving circuit.
Note that the current drive circuit of the organic EL panel has a reference current generation circuit in the input stage, and a drive stage and an output stage are provided for each pin of the organic EL panel. The drive stage includes a reference current distribution circuit that distributes a reference current corresponding to each pin and a current switching D / A having a current mirror configuration provided for each pin, and the D / A receives display data. In the output stage, there is an output stage current source composed of a current mirror circuit provided for each pin. Here, the D / A and the output stage current source provided corresponding to the pins are formed mainly by a current mirror circuit in which a large number of unit transistors are connected.
In this case, the unit transistors constituting the D / A and the current mirror of the output stage current source are such that the direction orthogonal to the pad arrangement direction (corresponding to the column direction) connected to the pins of the organic EL drive circuit is the longitudinal direction. In the rectangular transistor array block 3a, the unit transistors 1 are configured in an array of 252 and 42 × 6. The transistor array block 3a is repeatedly formed at a pitch of 3 pads in the pad array direction (lateral direction) with a predetermined gap therebetween.
In each transistor array block 3a, unit transistors 1 constituting current mirrors are selected in units of 3 × pad pitch width, and R, G, B output stage current sources and D / A conversion circuits (D / A) To form each current mirror circuit.
[0012]
Here, it is assumed that the number of transistors in the current mirror circuit of the output stage current source is 10 and the number of transistors in the D / A current mirror circuit is 70, and each has two spare or dummy transistors. The output stage current source and D / A are provided corresponding to R, G, B in units of 84. Therefore, the total number of unit transistors in the transistor array block 3a is 84 × 3 = 252.
That is, for simplicity of explanation, 252 unit transistors 1 identical to those in FIG. 3 are formed. As a result, six transistors can be formed in a pad pitch width of three times, so that six transistors can be arranged in the horizontal direction and 42 transistors can be arranged in the vertical direction. This is the transistor array block 3a.
In this case, the spacing between the arrangement blocks can be three times that in the case of FIG. 3, but if this spacing is the same as in FIG. 3, the width in the horizontal direction of each unit transistor 1 can be increased accordingly. Therefore, the integration efficiency is increased.
[0013]
As shown in the figure, a B (blue) transistor region is shown as a region of the current mirror circuit constituting the output stage current source on the pad 2 side of the transistor array block 3a, and this region is a current source 4Bi as 2 × 6 regions. A current mirror circuit is configured with the upper wiring layer by the ten transistors, and the output of the current mirror circuit is connected to the pad 2Bi through the upper wiring line 9b. In the current source 4Bi, ten transistors are used, and the remaining two are spare or dummy transistors.
Assuming that the pad 2Bi side is the front, the transistor region constituting the current source of the R (red) current mirror is arranged behind the pad 2Bi side, as shown in FIG. And Similarly, a current mirror circuit is constituted by 10 transistors each, and the output of the current mirror circuit is connected to the pad 2Ri via the upper wiring line 9r.
Further, behind that, as shown in the figure, the transistor region that constitutes the current source of the G (green) current mirror is assigned as a 2 × 6 region, which is assigned to the current source 4Gi. Similarly, a current mirror circuit is formed by 10 transistors each, and the output of the current mirror circuit is connected to the pad 2Gi through the upper wiring line 9g.
In the figure, pad 2Bi, pad 2Ri, pad 2Gi, pad 2Bi + 1, pad 2Ri + 1, pad 2Gi + 1,... Correspond to pad 2 in FIG.
[0014]
Behind these, current switching D / A of the current mirror configuration is 12 × 6 areas, corresponding to B, R, and G in this order, D / A5Bi, D / A5Ri, and D / A5Gi is assigned, and each D / A is composed of 70 transistors, and two transistors are spare or dummy transistors.
If more unit transistors, spare or dummy transistors are needed, for example, each D / A of B, R, G is formed as 13 × 6 regions, and the transistors of the array block 3a are formed. Increase the total number. In this case, 45 × 6 = 270 may be used.
By the way, the number of the above-mentioned unit transistors 252 is converted into two or n when one transistor is formed that is substantially twice or n times the area of the unit transistor. It is a numerical value. Conversely, when two or n transistors, each of which is an integral number of unit transistors, are partially formed, the values are converted to one as a whole.
The output terminal of the D / A 5 Bi is connected to the input terminal of the current source 4 Bi through an upper wiring line 8 b. The output terminals of D / A5Ri and D / A5Gi are connected to the corresponding input terminals of the current drive circuit through the current source 4Ri, the current source 4Gi, and the wiring lines 8r and 8g, respectively.
Such a transistor array block 3a is laid out for each of the three pads B, R, and G.
At this time, the transistor region forming the current mirror circuit for each of the B, R, and G D / A is selected from the 12 × 6 transistor array, and is formed by the current mirror connection in the upper layer. . Since the 12 × 6 region has a configuration in which 6 × 6 regions close to a square are vertically arranged in two stages, the paired transistors of the current mirror configuration are close to each other, and the wiring can be shortened. As a result, the transistors can be selected at a close distance, so that the pair characteristics of the transistors are ensured.
Note that the region shape here is not a graphic shape, but is viewed from the transistor arrangement with the number of transistors as a unit, and the actual graphic shape varies depending on the width and length of the unit transistor 1.
[0015]
FIG. 2 shows another embodiment in which B, R, and G current source blocks are arranged in the horizontal direction corresponding to the pads, and only D / A is set in the vertical direction to B, R, and G. Are arranged in this order. Therefore, since the other structure is the same as FIG. 1, detailed description is omitted.
In FIG. 2, the wiring between the D / A and the output stage current source is omitted.
[0016]
Incidentally, in FIG. 1 and FIG. 2, the reference current generation circuit that is an input stage of the current drive circuit and the reference current distribution circuit that distributes the reference current to each pin that is a part of the drive stage are not shown.
On the other hand, when the pad 2 side is the front, the reference current distribution circuit is formed by the transistors arranged on the rear side of the transistor array block 3a. Further, since the reference current generating circuit usually receives an external resistor or a constant voltage from the outside, its circuit position is determined according to the layout of each circuit.
[0017]
In the embodiment shown in FIGS. 1 and 2 , for convenience of explanation, a rectangular transistor array block 3a is formed in the lateral direction of the transistor (R, G, B as a unit and a pad pitch of 3 times as a unit. Of course, the transistor array block 3a may be formed in a width that is an integral multiple of the pad pitch of 3 times.
In the above embodiment, the width of the two transistors is made to correspond to the pad pitch in accordance with the example of FIG. 3, but the width of the unit transistor (corresponding to the width in the pad arrangement direction) is substantially ½. Then, 12 transistors can be arranged in a width of 3 × pad pitch. Therefore, the D / A region is a square region as viewed from the arrangement of 12 × 12 transistors. Conversely, five transistors may be arranged in a width of 3 × pad pitch.
[0018]
Since the width of the transistor in the horizontal direction (corresponding to the pad arrangement direction) can be freely determined in design, the number of transistors that fall within the pad pitch width of 3n times (n is a positive integer) is better and is particularly limited. Is not to be done. In short, the number of transistors in the lateral direction (pad arrangement direction) may be an integer of 4 or more with respect to a pad pitch of 3n times.
The reason is that the current switching D / A of the current mirror configuration is a two-digit D / A having a weight of 1 or 2 when the smallest configuration is considered. In this case, three output transistors and two switch circuits are required for one input-side transistor, and a total of five transistors are required. If three pieces are taken in the horizontal direction, the vertical direction is two steps, which is a 2 × 3 rectangular area. On the other hand, when arranged as two rows in the vertical direction as shown in FIG. However, in the case of a D / A of 3 digits or more, a quadruple weight and one switch circuit are added, so 10 output side transistors are required.
In this case, the rectangular transistor arrangement block can be made into 3 × 4 areas, but when arranged in two columns in the vertical direction as shown in FIG. 3, it becomes 2 × 5, and the distance in the vertical direction is 2 × 5. It grows and it becomes difficult to secure the pair property.
Therefore, in this invention, (when the three digits or more D / A conversion in other words carried out) when an array of four or more bets transistor transversely to 3n times the pad pitch, pairs characteristic of the output transistor However, it is possible to secure more accurate D / A conversion than in the case of FIG.
[0019]
As described above, in the embodiment, the number of transistors of the output stage current source is set to 10, the number of D / A transistors is set to 70, and each of the two spare transistors is described as 84 units. However, the present invention is not limited to this number.
In the embodiment, both the D / A and the current source are rectangular, and the boundary line is linear. However, even if the boundary line is somewhat uneven or partially L-shaped, each current mirror There is substantially no problem because the layout can shorten the distance between the transistors constituting the circuit.
In particular, by selecting a rectangle having a width in the horizontal direction as in the embodiment, the selection of the pair characteristic transistors constituting the current mirror circuit spreads in the horizontal direction. Therefore, there is a higher probability that the characteristics are aligned than when selecting the transistors in the vertical direction.
Furthermore, in the embodiments, a bipolar transistor is taken as an example, but it goes without saying that the present invention can be applied even if a MOSFET transistor is used instead of the bipolar transistor.
[0020]
【The invention's effect】
As described above, in the present invention, a rectangular transistor arrangement block having a width of 3n times the pad pitch provided corresponding to the pin and in which four or more transistors are arranged in this width. , The current switching D / A of R, G, B is arranged in a direction perpendicular to the pad arrangement direction to form a current mirror circuit of each D / A that receives display data.
In this way, the D / A corresponding to the R, G, B pins is provided corresponding to the pad pitch width of 3n times without corresponding to each pad, and the R, G, B circuits are provided in the vertical direction. By laying out and making an IC, when a current mirror circuit is configured, the distance between transistors connected to the current mirror can be made shorter than in the past. As a result, the wiring line can be shortened, and a transistor with matched pair characteristics can be selected as the output side transistor of the current mirror circuit.
As a result, a highly accurate D / A conversion circuit can be obtained, and an organic EL drive circuit and an organic EL display device that can output a drive current with high integration efficiency and high accuracy can be easily realized.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a layout of a unit transistor constituting a D / A of a current drive circuit and a current mirror of an output stage current source of an embodiment to which an organic EL drive circuit of the present invention is applied.
FIG. 2 is an explanatory diagram of a layout of unit transistors constituting a D / A and a current mirror of an output stage current source according to another embodiment of the present invention.
FIG. 3 is an explanatory diagram of a unit transistor array in a region for forming a current driving circuit of an organic EL display panel in the prior art, in which (a) is a transistor array block, and (b) is a current The top view of the unit transistor which comprises a mirror, and (c) are the sectional drawings.
[Explanation of symbols]
1 ... unit transistor, 2 ... pad,
3, 3a ... Unit transistor array block,
4Bi, 4Ri, 4Gi ... current drive circuit,
5Bi, 5Ri, 5Gi ... D / A,
6bi ... output terminal, 7bi ... input terminal,
8b, 8r, 8g, 9b, 9r, 9g ... wiring lines,
10: Column driver IC.

Claims (4)

In an organic EL driving circuit for driving an organic EL panel with current through terminal pins of the organic EL panel provided corresponding to display colors of R, G, and B,
A plurality of pads provided corresponding to the terminal pins and connected to the terminal pins;
A current switching D / A conversion circuit of a current mirror configuration provided corresponding to the pad and receiving display data and generating an analog current for display corresponding thereto;
A plurality of pads provided corresponding to the R, G, and B that are provided corresponding to the pads and are driven by an output current from the D / A conversion circuit and output a drive current to the terminal pins via the pads. A current source;
A plurality of transistors having a width in the pad arrangement direction substantially corresponding to 3n times the pad pitch in the arrangement direction of the pads (n is a positive integer) and four or more transistors are formed with respect to this width. A rectangular transistor array block having
Transistors constituting the current mirror circuit of the D / A conversion circuit in which the D / A conversion circuits of R, G, B are arranged in a direction perpendicular to the pad arrangement direction in the transistor arrangement block Is selected and integrated into an IC ,
The plurality of current sources corresponding to R, G, and B each have a current mirror circuit, and are allocated between the D / A conversion circuit and the pad in the transistor array block. An organic EL driving circuit in which transistors constituting a current mirror circuit are selected . 2. The organic EL drive circuit according to claim 1 , wherein n is 1, and the transistor array block is configured such that at least 6 transistors are arranged in the pad array direction in a width three times the pad pitch. In an organic EL display device having an organic EL driving circuit for current-driving the organic EL panel through terminal pins provided corresponding to the display colors of R, G, and B of the organic EL panel,
A plurality of pads provided corresponding to the terminal pins and connected to the terminal pins;
A current switching D / A conversion circuit of a current mirror configuration provided corresponding to the pad and receiving display data and generating an analog current for display corresponding thereto;
A plurality of pads provided corresponding to the R, G, and B that are provided corresponding to the pads and are driven by an output current from the D / A conversion circuit and output a drive current to the terminal pins via the pads. A current source;
A plurality of transistors having a width in the pad arrangement direction substantially corresponding to 3n times the pad pitch in the arrangement direction of the pads (n is a positive integer) and four or more transistors are formed with respect to this width. A rectangular transistor array block having
Transistors constituting the current mirror circuit of the D / A conversion circuit in which the D / A conversion circuits of R, G, B are arranged in a direction perpendicular to the pad arrangement direction in the transistor arrangement block Is selected and integrated into an IC ,
The plurality of current sources corresponding to R, G, and B each have a current mirror circuit, and are allocated between the D / A conversion circuit and the pad in the transistor array block. An organic EL display device in which transistors constituting a current mirror circuit are selected. 4. The organic EL display device according to claim 3 , wherein n is 1, and in the transistor array block, at least 6 transistors are arranged in the pad array direction in a width three times the pad pitch.

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