JPH0247909A - Reference voltage generating circuti - Google Patents

Abstract

PURPOSE:To generate a reference voltage with a few circuits by providing a means applying voltage division by resistors twice and correcting an error caused at the voltage division. CONSTITUTION:Resistors R1-R4 are connected in series, one terminal is connected to a power potential and the other terminal is connected to ground level. A selection circuit 1 receives potentials from connecting points A to D, selects one potential by using selection signals S2, S3 and the result is outputted. A selection circuit 2 receives potentials from connecting points B to E, selects one potential by using selection signals S0, S1 and the result is outputted. One terminal of resistors R11-R14 is supplied to the output of the selection circuit 1 and the other terminal is connected to the output of the selection circuit 2. A selection circuit 3 selects potentials from connecting points F to I by using the signals S0, S1 to output an analog voltage V0. The value of correction resistors R21-R24 is equal to the series combined resistance of the resistors R11-R14, switches SW1-SW4 are controlled by using the signals S2, S3 to correct the voltage division correctly. Through the constitution above, number of resistors to obtain voltages of 16 steps, for example, is enough to be 12, the circuit is realized by using 3 sets of 4-input selection circuits and 4 switches, then the scale of the circuit is much reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a reference voltage generation circuit, and more particularly to a reference voltage generation circuit that generates a reference voltage by dividing one resistor.

[Conventional technology]

Conventionally, in this type of reference voltage generation circuit, a number of resistors corresponding to the required resolution are connected in series, and a voltage divided by the resistors is selectively output.

Here, a circuit for obtaining a reference voltage from 0/16×vDD to IV16×VDD with a 1/16-point resolution of the power supply voltage (hereinafter referred to as VDD) will be explained as an example.

Figure 6 is a block diagram of a conventional reference voltage generation circuit.
Sixteen resistors R101 to R116 are connected in series to divide the power supply voltage into 16 parts. The selection circuit 10 selects one of the 16 divided potentials and outputs the analog output Vo.The selection of the voltage is performed using the selection signals SO to S3, and the selection signal is determined according to the logic of the selection F1a1g7 as shown in the figure. SO～S
If 3 is n, select fl/16VDI) tap.

[Problem to be solved by the invention]

In the conventional base*voltage generation circuit described above, it was necessary to prepare as many resistors as the required resolution. Also,
The selection circuit also had to be manually selected for the number of resolutions required, resulting in an increase in circuit scale.

For this reason, when such a reference voltage generation circuit is implemented as an IC, there is a drawback that the tear 1 area of 1jIc increases, leading to an increase in cost. An object of the present invention is to provide a reference voltage generation circuit that reduces the number of resistors and the circuit scale of the selection circuit by performing voltage division using resistors twice.

[Means to solve the problem]

The reference voltage generation circuit of the present invention includes n resistors 81 to n.
A first resistor string is connected in series with one end connected to one source and the other end is grounded to divide the power supply voltage, and m resistors R11 to R1.
a second resistor string connected in series, a connecting means for selectively connecting the second resistor string in parallel to both ends of the resistor Rk (k heat 1 to n); selection means for selecting a divided voltage and outputting a reference voltage; and a selection means for selecting a divided voltage and outputting a reference voltage; and a correction means for selectively connecting n-1 correction resistors in parallel.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

The gt diagram is a professional diagram of one embodiment of the present invention.

The resistors 3l-R4ti are connected in series, one end being at power supply potential and the other end being at ground potential.

The connection point between the power supply and resistor 1 is point A (potential is 4/4
VDD) Connect the connection point between resistor 1 and resistor 2 to point B (potential is 3
/ 4 vDD) Connect the connection point between resistor 2 and resistor R3 to 0 point (potential is 2
/ 4 VDD) Connect the connection point between resistor 3 and resistance device 4 to point D (potential is 1/4 VDD).
4VDD) The connection point between resistor 4 and ground is called point E.

The selection circuit 1 uses the potential from point A to DJ as human power, and selects and outputs one potential using selection signals S2 and 83. ◎Second
The figure shows the selection logic. Selection circuit 2 This is a selection circuit that inputs the potential from point FiB to point E, selects the 11th place using selection signals S2 and S3, and outputs the selected result. 'isz diagram shows this selection logic.0 resistors kLtt-R14 are connected in series, one end is connected to the output of selection circuit 1, and the other end is connected to the output of selection circuit 2. The connection point with resistor 11 is point F, and resistor a
Select the connection point between ll and resistor 12 as 0 point, the connection point between resistor R12 and resistor 313 as point H, the connection point between resistance device 13 and resistor L 14 as 1 point, and select resistance device 14. The connection point with circuit 2 is called one point.

The selection circuit 3 inputs potentials from point F to one point, selects one potential using selection signals SO and 81, and outputs an analog output voltage vO. FIG. 3 shows the selection logic.

Figure 5 shows 11 choices qfi number 80~8375!100IB
(binary notation) is shown as an example. .

The selection circuit IFiB point (12/16Von) is changed to the selection circuit ZHC point (8/16VDD).
2/16 VDD ~ 8/16 Vnts tor. In order to select the M selection M3dI point, the output voltage Fi9/
l 6 VDD.

Here, by connecting the resistors 11 to R14 in parallel to the resistor 2, the partial voltage actually collapses to some extent. Therefore, the potential at point B is 12/l 6 V! ID is somewhat low 0
The potential at the point ti 8 / 16 is somewhat higher than VDD.

Resistor 321~R24Fi Correctly adjust this voltage to 4/16
This is a resistor for correcting VnB deviation.Sui, Te8W1~
When SW4 is turned on, it is connected in parallel to resistors B1 to R4, respectively. The resistance values of the resistance ratios 21 to R24 are 1 series, which is equal to the series resistance of the resistors R11 to R14.

The switches 8W1-8W4 are controlled by selection signals S2 and S3.
The control logic is shown in FIG.

In the case shown in FIG. 5, switches 8W1, SW3 and sw4
By turning on the switch SW2 and turning off the switch SW2, the
Point d 12/16 VnnK, point C 8/16 V
! It can be corrected to In. Therefore, one point can be 9/16 VDD and an accurate analog output voltage can be obtained.

As described above, according to the present invention, the number of resistors required to obtain, for example, 16 levels of voltage is 12 including those for correction, which can be realized using the conventional 16 75ES resistors.

Furthermore, although the voltage selection circuit required 16 manpower, it can be realized with three four-manpower selection circuits and four switches.

Although an example of 16 stages is shown here, for example, in order to obtain a voltage with 8-bit accuracy, that is, 256 stages, 256 Fi resistors were conventionally required, but according to the present invention, only 5 resistors are required. Since it can be realized with 48 resistors, which is less than one-fold, the circuit scale can be significantly reduced.

〔Effect of the invention〕

As explained above, the present invention can generate a reference voltage with a very small number of circuits by performing voltage division twice using resistors and having a means for correcting errors caused by the voltage division. Therefore, when this circuit is integrated into an IC, there is an effect that the IC can be supplied at a low cost.

[Brief explanation of the drawing]

FIG. 1 is a professional diagram of an embodiment of the present invention, and FIG. Figures 3 and 4 are explanatory diagrams showing the control logic of Figure 1;
Fig. 1 is a circuit diagram showing the operating principle of Fig. 1, Fig. 6 is an explanatory diagram showing the control logic of an example of the conventional system. 1.2.3... Selection circuit, 10... Selection circuit, 几l~ 4.几11～R14. R21-R24
゜几101~R116・・・Resistor, 8W1~S
W4...Switch, Sθ~83...Selection signal, Vo...Analog output. Agent Patent Attorney Susumu Uchihara Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] m
a second resistor string in which resistors R11 to R1m are connected in series; and the second resistor string is connected to the resistor Rk (k=1 to n).
connecting means selectively connected in parallel to both ends of the resistor Rk; selection means selecting the voltage divided by the second resistor string and outputting a reference voltage; and a resistor other than Rk in the first resistor string. and a correction means for selectively connecting in parallel n-1 correction resistors each having a value corresponding to the series resistance value of the second resistor string to each of the resistors. .