JP2000022543A - DA conversion circuit device - Google Patents

Abstract

(57) [Problem] To provide a DA converter circuit device that can be realized with a small current consumption and a small occupied area even when there are many input channels. SOLUTION: A plurality of input terminals, a single resistor string section 10, and a DA connected to the resistor string section 10 are provided.
A plurality of selector units 20 and 30 for selecting a conversion output voltage
And control circuit sections 40 and 50 for controlling the selector sections 20 and 30, and a plurality of DA conversion output terminals provided corresponding to the plurality of selector sections 20 and 30, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a DA converter circuit device formed on a semiconductor integrated circuit, and more particularly to, for example, a CM.
The present invention relates to a resistor string type DA conversion circuit device used for a semiconductor integrated circuit having an OS structure.

[0002]

2. Description of the Related Art Generally, a DA converter is used to convert a digital signal into an analog signal after processing. One of the DA conversion methods is a resistor string method.

FIG. 3 shows an example of a conventional 10-bit resistor string type DA converter. Here, 90 is a decoder circuit composed of NAND circuits for 10-bit input, 91 is a CMOS inverter circuit, 92 is a CMOS transfer gate circuit, and Rstr is a resistance element having a resistance value R. Vout indicates an analog output voltage. The resistance element Rstr is connected to the first voltage node 93 to which the upper limit value V _REFH of the analog output voltage is applied.
And the second lower limit value V _REFL of the analog output voltage is applied.
To form a resistor string. Since the resistor string type DA converter circuit selectively extracts a plurality of voltages divided by the resistor string, it has high accuracy and excellent monotonicity.

Next, the area occupied by the above-described resistor string type DA converter will be described. Generally, the n-bit resistor string method requires 2 ⁿ resistance elements Rstr and 2 ⁿ CMOS transfer gate circuits 92. In a general 10-bit resistor string type DA conversion circuit, the occupied area ratio of the analog section constituted by the resistor string section and the digital section constituted by the CMOS transfer gate circuit and the NAND circuit is equal to that of the analog section. The area is dominantly larger. Also, the current consumption of the resistor string type DA converter is dominated by the through current flowing through the resistor string section.

[0005]

That is, in the conventional resistor string type D / A converter described above, when the current consumption of each D / A converter is x (mA), the current consumption when the number of input channels is n is: x × n (mA), and when the number of channels is large, there is a problem that current consumption increases, an occupied area increases, and cost increases.

For example, a DA converter circuit built in a portable terminal requires a large number of channels, high conversion accuracy, a small occupied area (low cost), noise intensity, and the like. Recently, the number of conversion bits is large. There is also a strong demand for DA conversion in a multi-bit configuration. In the case of a configuration that satisfies the above-mentioned requirements for the channel, conversion accuracy, noise intensity, and multi-bit configuration, there is a problem of an increase in current consumption and occupation area.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a DA converter circuit which can be realized with a small current consumption and a small occupied area even when there are many input channels.

[0008]

In order to achieve this object, the present invention provides a plurality of input terminals, one resistor string section, and a plurality of selectors connected to the resistor string section for selecting a DA conversion output voltage. And a control circuit unit for controlling the selector unit, and a plurality of DA conversion output terminals provided corresponding to the plurality of selector units.

With such a configuration, a plurality of selector sections share one resistor string section. Therefore, compared to a case where a resistor string section is provided for each selector section, current consumption and current consumption are reduced. The occupied area can be reduced.

[0010]

According to the present invention, a plurality of input terminals, one resistor string, a plurality of selectors connected to the resistor string and selecting a DA conversion output voltage are provided. It has a control circuit section for controlling the selector section and a plurality of DA conversion output terminals provided corresponding to the plurality of selector sections.

More specifically, a DA converter circuit device according to an embodiment of the present invention includes a first voltage node to which an upper limit value V _REFH of an analog output voltage is applied, and a first voltage node to which the analog output voltage is applied. A resistor string portion composed of 2 ⁿ resistor elements connected in series between the second node to which the lower limit value V _REFL is applied, and all adjacent resistor elements and resistor elements And x selectors having terminals between which an input is provided as an input and a terminal for outputting one output voltage, and x controls for controlling the selector according to input data and outputting a desired output voltage. It is provided with a part.

As a result, a plurality of selector sections share one resistor string section, so that the current consumption and the occupied area are reduced as compared with the case where a resistor string section is provided for each selector section. can do.

According to a second aspect of the present invention, the resistor string section is provided in an AD conversion circuit mixedly mounted on the same LSI. Specifically, claim 2
In the D / A conversion circuit device according to the embodiment of the present invention described above, one resistor string portion is incorporated in one AD conversion circuit, and the resistor string portion receives the upper limit value V _REFH of the analog output voltage. This is constituted by 2 ⁿ resistance elements connected in series between one voltage node and a second node to which the lower limit value V _REFL of the analog output voltage is applied.

Thus, even when the number of channels of the DA converter is one, the current consumption and the occupied area of the DA converter can be reduced by using the AD converter.

According to a third aspect of the present invention, there are provided a plurality of buffer circuit sections respectively connected to a plurality of DA conversion output terminals. Specifically, the DA converter circuit device according to the embodiment of the present invention is connected to x DA conversion output terminals output from the selector unit, buffers the output voltage, and outputs the output voltage. Then, it has x buffer circuit sections for reducing the impedance of the terminal.

By performing impedance conversion in the buffer circuit section in this manner, it is possible to prevent the influence of an error caused by a load added to the output of the circuit from being transmitted to the selector section.

The selector section has one of the 2 ⁿ input terminals.
As means for transmitting a desired output voltage to the output terminals, for example, a CMOS transfer gate circuit is used. The control circuit is connected to a selector circuit to select any one of the 2 ⁿ input terminals and controls so as to output an output voltage corresponding to the input data.

The buffer circuit section has an input terminal connected to an output terminal of the DA converter circuit, and outputs an output voltage of the DA converter circuit from the output terminal. The impedance of the output terminal is smaller than the impedance of the output terminal of the DA converter.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram of a DA according to an embodiment of the present invention.
FIG. 3 is a circuit diagram illustrating a basic configuration of a conversion circuit. D shown in FIG.
The A conversion circuit has 2 bits and n bits (here, n = 1
0) from the digital input code to the output voltage V
out of the resistor string unit 1
0, two selector sections 20 and 30, and two control circuit sections 40 and 50.

The resistor string section 10 is connected in series between the first node 1 to which the upper limit value V _REFH of the analog output voltage is applied and the second node to which the lower limit value V _REFL of the analog output voltage is applied. Are connected to (2 ¹⁰ -1) resistance elements Rstr.

The selector section 20 includes a resistor string section 10
(2) between all the resistance elements Rstr and Rstr
A connection node ^10-2), by selecting only voltage of one of the nodes in a total of 2 ¹⁰ nodes between the first and second nodes, and outputs from the output node Vout1. In the selector section 20, a CMOS transfer gate circuit 10 is used as a selector element for selecting a node and transmitting a voltage.
3 is used. 102 is an inverter. The selector unit 30 has the same structure as that of the selector unit 20, and outputs from the output node Vout2.

The control circuit section 40 converts the input data of each channel, and connects to the selector section 20 to control each selector element, so that a desired output voltage corresponding to the input data of the channel 1 is output to the output node Vout1. The selector unit 20 is controlled so as to output more data. 100 is a decoder circuit. The control circuit unit 50 has the same structure as the control circuit unit 40, and the selector unit 30
To output a desired voltage from the output node Vout2.

The buffer circuit section 60 receives the node Vout1 as an input, and outputs an output voltage obtained by impedance-converting the input from the node DAout1. The buffer circuit unit 70 receives the node Vout2 as an input, and outputs an output voltage obtained by impedance-converting the input from the node DAout2. By converting the impedance, the influence of the error caused by the load applied to the node DAout1 is not transmitted to the node Vout1. Also, the influence of the error caused by the load applied to the node DAout2 is not transmitted to the node Vout2. By connecting the buffer circuit units to all the output nodes Vout, the transmission of the influence of the error between the output nodes to the commonly used resistor string unit 10 is greatly reduced.

FIG. 2 is a circuit diagram showing a basic configuration of a DA converter according to another embodiment of the present invention. In FIG. 2, one resistor string section 10 used inside the AD conversion circuit allows two channels of n bits (here, n = 10) as in the embodiment of FIG.
From the digital input code of D
to generate t. In FIG. 2, one resistor string section 80 and two selector sections 20 and 30 are connected.
And two control circuit units 40 and 50.

[0025]

As described above, according to the DA converter circuit device of the present invention, one resistor string section is shared by a plurality of selector sections for selecting a DA conversion output voltage. Thus, the current consumption and the occupied area can be reduced as compared with the case where a resistor string portion is provided, and a desired analog voltage can be output even when the number of channels is large.

[Brief description of the drawings]

FIG. 1 is a circuit diagram illustrating an example of a basic configuration of a DA conversion circuit device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram illustrating an example of a basic configuration of a DA conversion circuit device according to another embodiment of the present invention.

FIG. 3 is a circuit diagram showing an example of a conventional resistor string type DA converter.

[Description of Signs] 10 Resistor string section 20 Selector section 30 Selector section 40 Control circuit section 50 Control circuit section 60 Buffer circuit section 70 Buffer circuit section Rstr Resistance element

Claims (3)

[Claims] 1. A plurality of input terminals, one resistor string section, a plurality of selector sections connected to the resistor string section to select a DA conversion output voltage, and a control circuit section controlling the selector section. A DA converter circuit device having a plurality of DA conversion output terminals provided corresponding to the plurality of selector units. 2. The DA conversion circuit device according to claim 1, wherein the resistor string section is provided in an AD conversion circuit mixedly mounted on the same LSI. 3. The DA conversion circuit device according to claim 1, further comprising a plurality of buffer circuit units connected to the plurality of D / A conversion output terminals, respectively.