JPS5820028A - Code converter - Google Patents

Abstract

PURPOSE:To obtain a code converter with a low cost, by controlling a switch which switches the connection between the reference potential and the earth potential to be connected to a capacitor array by means of the code of a signal to be a converted. CONSTITUTION:In the case of D/A conversion, the connection between the reference potential V and the earth potential is inverted by actuating switches SWA and SWB by a controlsignal given from a decoder circuit 15 that supplies a digital signal. As a result, the position is inverted between a capacitor Cx connected to the reference potential of a capacitor array 3 and a capacitor Cy connected to the earth potential. Thus the analog voltage VOUT of positive and negative signals can be delivered with the control signal given from the decoder circuit 15. For the A/D conversion, the connection between the reference potential and the earth potential is inverted successively in a comparison mode and by actuating switches SWA' and SWB' with the control signal given from a decoder circuit 16. As a result, the position is inverted between the capacitors Cx and Cy. Thus the positive and negative analog input signals are obtained through the same decoder circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a single-reference potential type code converter, or a single-reference potential history analog-to-digital converter, using a capacitor array.
(hereinafter referred to as a digital-to-analog converter) and a single-reference potential type digital-to-analog converter (hereinafter referred to as a DA converter). Concerning a simple code converter circuit.

An example of a conventional single reference potential WDA/MU DJR converter is shown in FIG. 1, FIG. 6, FIG. 6, and FIG. 12.
Figure ~Figure 4, Figure 7~! It is shown in Figure 11. In the figure, 1., 8 decoder circuit, 2 buffer amplifier circuit, 3.10 capacitor array, 4.11 selector circuit, 5.129
1 a decoding circuit for positive signals, 6.13 a decoding circuit for negative signals, 7 a comparator, 9.14 a sequential comparison register, C1
~C3 is each capacitor of the capacitor play, Cum is the sum of each capacitor of the capacitor play, SW, ~8 Wn
is a capacitor array switch, SWG* 8WC*
8WD is a switch, ■ is a reference potential, Vout is an analog output, MIN is an analog input, CX and CY are connected to a reference potential or ground potential, and the sum of the capacitors is CX + CY.
- First, we will explain using the example of a DA converter. In this case, the operating modes are divided into positive signal output and negative signal output, and within that, they are also divided into discharge mode and output mode. The discharge mode for positive signal output and the discharge mode for negative signal output are shown in Figure 2 and 411i1, respectively, and the output peak mode is shown in Figure 3. is the same as in the case of , but shows the output voltage; the configuration of the capacitor array 30 and the capacitor is different. The output voltage in the case of a positive signal is as shown by the following equation (1)K.

The output voltage when the negative signal is O is as shown in the following equation (2).

From equations (1) and (2), the switches Sw1 to 8 of the conductor play 3 shown in FIG. 1 in the case of a positive signal and the case of a negative signal.
Since it can be seen that the control signals that operate Wn are different, the conventional ODA converter has a decoder circuit IK that generates a control signal applied to the capacitor play 3 from a digital input signal as shown in Fig. 5. It requires a signal decode circuit S, a negative signal decode circuit 6, and its select circuit 4, which has the disadvantage that the decoder circuit 1 is complicated and the circuit scale becomes large.

Next, an example of an AD converter will be explained. In this case, Maz II7
All capacitors C in the capacitor array are discharged as shown in the figure. Next, as shown in Figure 8, change the analog input to Vl)
i) is input, and the output of the comparator 7 determines whether it is a positive signal or negative No. 11. Next, in the case of a positive signal, the analog voltage is sampled in the sampling mode shown in FIG. 9, and in the case of a negative signal, in the sampling mode shown in FIG. 11, to charge the total capacitor play. Then the 10th
In the successive approximation mode shown in the figure, the input pressure of the comparator 70 becomes O to obtain a digital output. Positive 4
In the case of No. 1, the charge C charged in the capacitor C in the sampling mode is expressed by the linear equation (3).

Q=OA (VIN-V)=”・(3) Next, in the successive approximation mode, capacitors CX and CY are connected.

Since the input voltage of the comparator 67 is set to O by changing the ratio, the analog input voltage is expressed by the following equation (x).

In the case of a negative signal, the charge Q that charges the conductor ytcm in sample mode is calculated by the following formula (Q m CA V I
w = ”” (Successive ratio 1m for the first time! Jl-de = Ndensa Cx and CY.

Since the ratio is changed and the ratio asyo input voltage O is 1, the analog input voltage is expressed by the following formula (@).

The value shown in the above equation (4×6) is taken out as a digital output.

From the formula (4
It can be seen that the control signals that operate the are different.

For this reason, in the conventional ADK converter, as shown in FIG. 12, a decoder circuit 8 that generates a control signal applied to a capacitor array 10 from an analog input signal includes a positive signal decoding circuit 12, a negative signal decoding circuit 13, The drawback is that it requires Id path 11 and the decoder circuit 8i is complicated and the device becomes large, as in the case of DA converter.
In order to eliminate the above-mentioned drawbacks, in a leather-reference potential 11:l capacitor array type code converter,
An object of the present invention is to provide a code converter whose decoder circuit can be simplified and made inexpensive by switching the connection between a reference potential and a ground potential depending on the positive and negative signals O to be converted.

To achieve the above object, the present invention includes a rounding array of 1 decoders, a switch for selectively connecting each capacitor of the capacitor array to a reference potential or ground potential, and a decoder circuit connected to the array. A single-reference potential type = capacitor array code converter comprising: a switch for switching the connection of the reference potential and ground potential connected to the capacitor array; and the switch is controlled by the sign of the signal to be converted. The present invention provides a code converter characterized by:

Embodiments of the present invention will be explained below with reference to the drawings.
The figure is a block diagram of the DA converter of the present invention, and the figure 1s14 is a block diagram of the AD converter of the present invention.

In the figure, parts with the same functions as those in Figure 12 are indicated by the same symbols.@Is, 16 is a decoder circuit, 1? is a successive approximation register,
8W, 5w1t, swA', 8WB' reference potential and ground potential changeover switch, capacitor play 3.10 circuit diagrams shown in Figures 1 and 6. First, the case of the DA converter will be explained. For example, if the output signal shown in #13111 is a negative signal, the connection between the reference potential and the ground potential is reversed by operating the switches 8WA and 8WB by the control signal from the decoder circuit 15. This allows condan tcz, c
Since the position of y is reversed, the output voltage linear equation (as shown in the force @, that is, the (IM?) equation) corresponds to (2) 2. Switch S of capacitor array 3
It can be seen that the control signals for operating W1 to Wn may be the same.

Next, in the case of an AD converter, as an example, in the case of a negative signal, in the successive approximation mode shown in FIG. 8WB' is operated and inverted. ◇As a result, the capacitor CHI CTO position is reversed, so the analog input voltage becomes It can be seen that the control signals for operating the switches SWI to BWh of the capacitor array 10 may be the same.

In other words, in both the DA converter and AD converter, the decoder circuit 1! S, 16 capacitor array3. It can be seen that there is no need to consider the control signals of the switches SW and -8Wn separately for positive and negative signals, and that the It path also becomes simpler in terms of construction costs.

As explained in detail above, according to the present invention, the decoder circuit configuration of a capacitor array type code converter with a single reference potential can be easily configured and the circuit scale can be reduced, resulting in an effect of lowering the cost.

[Brief explanation of the drawing]

FIG. 1 II/E5 is a boot-stack configuration diagram of an example of a conventional DA converter, FIG. 6, FIG. FIG. 14 is a block diagram of an example of a four-way converter, FIG. 14 is a block diagram of an example of an OAD converter of the present invention, and FIGS. FIG. 3 is a diagram of the operating principle of an AD converter. 1 in the figure. 8. 15. lfi is a decoder circuit, 2
3.10 is a capacitor array, 4.
11 is a selector circuit, S and tZ are positive signal decoding circuits, 6.13 is a negative signal decoding circuit, 7 is a comparator, 9,
14.17 is a successive approximation register, C1 to Cm are each capacitor of the capacitor play, the sum of each =nd yv- of the Cod sensor array, SW1 to 8Wn are the switches of the capacitor play, 8WA, 8WB, 8WA', 8WB' ,
8WD. 8WG is a switch, V is a reference potential, VOUT is an analog output, vIN is an analog input, CXtcy is a capacitor connected to a reference potential or ground potential. 8th '4 q vn V 5#10 mouthpiece 110 11zti'1 wC

Claims (1)

[Claims] A single-reference potential type capacitor array type code comprising a capacitor array, a switch for switchingly connecting each capacitor of the capacitor array to a reference potential type ground potential, and a nine-dimensional circuit connected to the capacitor array. 1. A code converter, characterized in that the converter is equipped with a switch for switching the connection of a reference potential connected to a capacitor array and a ground potential, and the skeleton switch is controlled according to the sign of a signal to be converted.