JP2564009B2 - D / A converter - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a matrix cell type D / A converter in which cells having the same function are arranged in a matrix.

[Conventional technology]

A conventional matrix cell type D / A converter of this type is shown in FIG. 3 by taking 4 bits as an example. In the figure, 1 is a first digital input terminal, is a terminal for inputting the upper 2 bits of 4 bits of the input digital code, and 2 is a second
Input digital code 4
This is a terminal for inputting the remaining lower 2 bits of the bits. Reference numeral 4 is a first decoder circuit to which the first signal line groups 101 to 105 are connected to the output, and 5 is a second signal line group 201 to 204 to the output.
Is a second decoder circuit connected to, and 11 is a fourth
A third cell whose internal structure is shown in the drawing, and 600 is a third cell array in which the third cells are arranged in a matrix.

The internal structure of the third cell is shown in FIG. In this figure, 6 is a control signal for generating a control signal to be supplied to the third cell by using a signal obtained from a signal line in the first signal line group and a signal line in the second signal line group. This is a logic circuit for generation, and in this logic circuit 6, at least two of the three input signal lines 101, 102, 201 are "H".
If so, "H" is output to the control signal output terminal 7. 7'is the output of the current source circuit 10 D / A conversion output line 3
00 is a control signal input terminal in the changeover switch 9 which is connected to 00 by the control signal.

 Next, the operation will be described.

Now consider the case where the input digital code is 4 bits. Of the 4-bit digital code, the upper 2 bits are input to the first digital input terminal 1 and the remaining lower 2 bits are input to the second digital input terminal 2. In the first decoder circuit 4, the first signal line groups 101 to 105
To the second signal line group 201 to 204 in the second decoder circuit 5. Signals obtained from 101 and 102 of the first signal line group are input to cells arranged in the first row of the third cell array 600, and first signals are input to cells arranged in the second row. 102 out of the line group,
A signal obtained from 103 is input, a signal obtained from 103 and 104 of the first signal line group is inputted to the cells arranged on the third row, and a first signal is inputted to the cells arranged on the fourth row. Signals obtained from 104 and 105 of the signal line group are input.

A signal obtained from 201 of the second signal line group is input to the cells arranged in the first column of the third cell array, and the cells arranged in the second column are supplied with the second signal. The signal obtained from 202 of the signal line group is input, and the signal obtained from 203 of the second signal line group is input to the cells arranged in the third column and arranged in the fourth column. A signal obtained from 204 of the second signal line group is input to the cell.

In each third cell, the control signal generating logic circuit generates a current source output and a D / A conversion output line based on the three signals supplied from the first signal line group and the second signal line group. A control signal for controlling the change-over switch 9 for connecting to and is generated.
With the above operation, the output current corresponding to the input digital code can be obtained by turning on the third cells in the number corresponding to the input digital amount.

[Problems to be Solved by the Invention]

The conventional matrix cell type D / A converter includes a logic circuit for generating a current source switch control signal in each cell that constitutes the cell array as described above, and the area of each cell itself increases. Since the area of the entire cell array becomes large, there is a large variation in the characteristics between the current source circuits, which causes the deterioration of the characteristics of the D / A converter. To explain this problem in more detail, it is said that the increase in the area of the entire cell array increases the chip size and the length of the ground line, resulting in a rise in the potential. Therefore, the bias conditions that should be the same in all cells differ depending on the cell position, and the output current amount has a surface distribution according to the cell position.

Further, when the constituent elements of each cell are only the current source circuit and the changeover switch, it is necessary to run as many current source switch control signal lines as the number of cells forming the cell array in the cell array, and the logic circuit is provided for each cell. Even if the area of each cell is reduced by deleting it from the inside, a large number of signal lines must run in the cell array for the above reason, and the area of the cell array becomes large in the end. However, these problems have been such that the greater the number of bits (resolution) of the D / A converter, the greater the characteristic deterioration of the D / A converter.

The present invention has been made in order to solve the above-mentioned problems of the conventional ones, and it is possible to suppress the variation of the current source of each cell and also reduce the chip size.
The purpose is to obtain a D / A converter.

[Means for solving the problem]

A D / A converter according to the present invention has a unit current source circuit and a changeover switch for connecting the current source output to a D / A conversion output line as one cell, and the cells are formed in a matrix in the same layer. The other digital circuit including the logic circuit for generating the control signal to be supplied to the changeover switch in each cell is formed in another layer.

Further, the D / A converter according to the present invention is arranged in a matrix, and a plurality of cells connected to the D / A conversion output line,
In a D / A converter including a decoder circuit that outputs a predetermined signal to the plurality of cells based on an input digital code that is input, each of the plurality of cells is formed in a first layer and controlled. A control signal generating logic circuit having a signal output terminal for receiving a predetermined signal from the decoder circuit and outputting a control signal based on the received predetermined signal to the control signal output terminal; and the first layer. A current source circuit formed on a second layer that is a layer different from
Of the control signal generating logic circuit, the control signal output terminal of the control signal generating logic circuit and a control signal input terminal electrically connected through a through hole, the current source circuit and the D /
A changeover switch connected between the A conversion output line and ON / OFF controlled by a control signal from the control signal generating logic circuit input to the control signal input terminal Is.

[Action]

The D / A converter according to the present invention has a unit current source circuit and a changeover switch as one cell, is formed in a matrix in the same layer, and has another digital circuit including a logic circuit for generating a control signal to be supplied to the changeover switch. Since the circuits are formed in other layers and signals are transmitted and received between the layers through the through holes, the area of the current source cell array can be reduced, and the current source circuit between the cells forming the cell array can be reduced. It is possible to reduce variations in characteristics, reduce the area of the D / A converter itself, and improve characteristics.

Further, the D / A converter according to the present invention is arranged in a matrix, and a plurality of cells connected to the D / A conversion output line,
In a D / A converter including a decoder circuit that outputs a predetermined signal to the plurality of cells based on an input digital code that is input, each of the plurality of cells is formed in a first layer and controlled. A control signal generating logic circuit having a signal output terminal for receiving a predetermined signal from the decoder circuit and outputting a control signal based on the received predetermined signal to the control signal output terminal; and the first layer. A current source circuit formed on a second layer that is a layer different from
Of the control signal generating logic circuit, the control signal output terminal of the control signal generating logic circuit and a control signal input terminal electrically connected through a through hole, the current source circuit and the D /
Since it has a changeover switch which is connected between the A conversion output line and is turned on / off by a control signal from the control signal generating logic circuit input to the control signal input terminal. , The area of the current source cell array can be reduced, the variation in the characteristics of the current source circuit among the cells forming the cell array can be reduced, the area of the D / A converter itself can be reduced, and the characteristics can be improved. it can.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

1 and 2 are views showing a D / A converter according to an embodiment of the present invention. In FIG. 1, reference numeral 1 is a first digital input terminal, a terminal for inputting the upper 2 bits of the input digital code 4 bits, 2 is a second digital input terminal, and the rest of the input digital code 4 bits. This is a terminal for inputting the lower 2 bits of. 3 is the first
Of the cell array of the first cell, 4 is a first decoder circuit whose outputs are connected to the first signal line groups 101-105, and 5 is an output which is connected to the second output line groups 201-204. The second decoder circuit.

FIG. 1 (a) shows the first cell array constituting the first cell array.
6 is a diagram showing the internal configuration of the cell of FIG. 6, in which a control signal 6 is generated using signals obtained from the signal lines of the first signal line group and the signal lines of the second signal line group. 7 is a control signal output terminal.

FIG. 2 is formed in a layer different from the layer in which the structure shown in FIG. 1 is formed, and in the drawing, 8 is a second cell constituting the second cell array 500, The internal structure of the cell is shown in FIG. In the figure, 7'is a control signal input terminal, 9 is a changeover switch which is turned on / off by a control signal inputted to the control signal input terminal 7 ', 10
Is a current source circuit.

 Next, the operation will be described.

Consider the input digital code as 4 bits. The upper 2 bits of the 4-bit digital code are the first
, And the remaining lower 2 bits are input to the second digital input terminal 2. The first decoder circuit 4 outputs signals to the first signal line groups 101 to 105, and the second decoder circuit 5 outputs the second signal line group 20.
Outputs signals to 1 to 204. Signals obtained from 101 and 102 of the first signal line group are input to the first cells arranged in the first row of the first cell array, and the first cells arranged in the second row are supplied to the first cells. Is 102,10 of the first signal line group
The signal obtained from 3 is input, the signals obtained from 103 and 104 of the first signal line group are input to the first cells arranged in the third row, and the first cells arranged in the fourth row are input. Signals obtained from 104 and 105 of the first signal line group are input to the cell.

In addition, a signal obtained from 201 of the second signal line group is supplied to cells arranged in the first column of the first cell array, and a signal obtained from 202 of the first cells arranged in the second column. The signal obtained is 203 in the first cell arranged in the third column.
The signals obtained by 204 are input to the first cells arranged in the fourth column. Each first cell generates a control signal based on the three signals supplied from the first signal line group and the second signal line group.
The control signal generated here is input to the control signal input terminal 7'in each second cell forming the second cell array formed in the formation through the through hole. In the second cell array, the sum of the current source outputs in the second cell selected by the input control signal is obtained as the D / A conversion output.

As described above, according to this embodiment, the current source circuit and the changeover switch circuit are arranged in a matrix in the same layer as one cell, and the logic circuit for supplying the control signal to the changeover switch circuit is provided in the other layer. Since the cells are formed, the cell size can be reduced, the variation of the current source circuit among the cells can be suppressed, and the chip size can be reduced.

In the above embodiment, the case of the 4-bit D / A converter has been described, but the same effect can be obtained not only for 4-bit but also for an n-bit D / A converter.

〔The invention's effect〕

As described above, according to the present invention, only one unit current source and a changeover switch that connects the unit current source output and the D / A conversion output line by a control signal are used as one cell, and this cell is arranged in a matrix form. Other digital circuits laid out in the same layer in area, including a digital signal input section and a logic circuit for generating a control signal to be supplied to the changeover switch, are formed in another layer and controlled between the layers through through holes. Since the laminated structure for transmitting and receiving signals is adopted, the current source cell array can be formed in a small area, which suppresses the variation in the characteristics of each current source circuit in the cell array, and D / The A conversion characteristic can be improved, and the laminated structure has an effect that the area of the D / A converter can be reduced at the same time.

Further, according to the present invention, they are arranged in a matrix,
In a D / A converter including a plurality of cells connected to a D / A conversion output line, and a decoder circuit that outputs a predetermined signal to the plurality of cells based on an input digital code that is input, Each of the plurality of cells is formed in the first layer and has a control signal output terminal, receives a predetermined signal from the decoder circuit, and outputs a control signal based on the received predetermined signal to the control signal output terminal. A control signal generating logic circuit for outputting, a current source circuit formed in a second layer different from the first layer, and a control signal generating logic circuit formed in the second layer. Has a control signal input terminal electrically connected to the control signal output terminal through a through hole, is connected between the current source circuit and the D / A conversion output line, and is input to the control input terminal. The control signal generating logic Since it is provided with the changeover switch which is turned on / off by the control signal from the circuit, the current source cell array can be constructed in a small area, whereby the characteristics of each current source circuit in the cell array can be improved. Variation will be suppressed to a small level,
The improvement of D / A conversion characteristics can be achieved, and further, by adopting a laminated structure, it is possible to simultaneously achieve the reduction in area as a D / A converter.

[Brief description of drawings]

1 and 2 are diagrams showing a D / A converter according to an embodiment of the present invention. FIG. 1 is a constitutional view of layers forming a digital circuit including a control signal generating logic circuit, and FIG. The figure shows the structure of a layer that forms cells in a matrix with only unit current sources and changeover switches. Fig. 3 shows a conventional matrix cell type D / A converter. Fig. 4 shows the structure. It is a figure which shows the internal structure of the cell. In the figure, 1 is a first digital input terminal and 2 is a second digital input terminal.
Digital input terminal, 3 is a first cell forming a first cell array, 4 is a first decoder circuit for generating first signal line groups 101 to 105, and 5 is a second signal line group 201 to 204. , A control signal generating logic circuit, 7 a control signal output terminal, 8 a second cell constituting the second cell array 500, 7'a control signal input terminal, 9 Is a changeover switch for turning on / off, and 10 is a current source circuit. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (2)

(57) [Claims] 1. Unit current sources are arranged in a matrix, and the output terminals of the current sources are commonly connected to each other through a changeover switch to provide D / A conversion output, which corresponds to a digital code input to a digital input terminal. In the D / A converter configured to output the output current corresponding to the input digital amount as a current output from the D / A conversion output terminal by controlling the on / off of the changeover switch by the control signal generated by the logic circuit. A control signal generation circuit for arranging the unit current source and a changeover switch corresponding to the unit current source as one set, laying out a plurality of the same in the same layer in a matrix, and controlling each of the current source switches. Other digital circuits including the same are formed in a layer different from the above layer, and a control signal is transferred between the two layers by an interlayer connecting means. D / A converter, characterized in that the. 2. A plurality of cells arranged in a matrix and connected to a D / A conversion output line, and a decoder circuit for outputting a predetermined signal to the plurality of cells based on an input digital code inputted. In the D / A converter provided with, each of the plurality of cells has a control signal output terminal formed on the first layer, receives a predetermined signal from the decoder circuit, and receives a predetermined signal. A control signal generating logic circuit for outputting a control signal based on the above to the control signal output terminal; a current source circuit formed on a second layer different from the first layer; Formed in a layer, having a control signal input terminal electrically connected to the control signal output terminal of the control signal generating logic circuit through a through hole, the current source circuit and the D / A conversion output line Connected between the above control signals A D / A converter comprising: a changeover switch which is on / off controlled by a control signal from the control signal generating logic circuit input to the input terminal.