JPS631365A - Reference voltage generator circuit - Google Patents

Abstract

PURPOSE:To reduce noises from a power source and other signal line by inserting smoothing condensers between the output voltage of a voltage controller and one power terminal voltage, and between the output voltage of the controller and other power terminal voltage. CONSTITUTION:Smoothing condensers C2, C1 are respectively inserted between the output voltage Vc of a voltage controller and one power terminal voltage Vcc, and between the output voltage Vc and the other power terminal voltage Vss in the voltage smoothing circuit of a reference voltage generator 1. The influence of a power source variation with respect to the output voltage Vc can be completely cancelled by equalizing the capacities of the condensers C1, C2.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a reference voltage generation circuit incorporated in a large-scale integrated semiconductor device.

BACKGROUND OF THE INVENTION In recent years, as semiconductor devices have become more integrated on a large scale, their functions have also become more diverse. Under these circumstances, various modes have been detected by incorporating a reference voltage generation circuit into a semiconductor device and comparing the reference voltage generated by the circuit with the voltage of a signal applied to an external terminal. At this time, generating an accurate reference voltage has become a requirement for realizing high performance and stable operation of semiconductor devices.

A conventional reference voltage generation circuit will be explained below. FIG. 3 shows a circuit diagram of an example of a conventional reference voltage generation circuit incorporated in a semiconductor device.
FIG. 4 schematically shows waveforms during operation of this semiconductor device.

In FIG. 3, the circuit within the broken line indicated by 1 is the reference voltage generating circuit, which is incorporated within the semiconductor device 2 here. That is, in addition to the reference voltage generation circuit, this semiconductor device 2 includes an internal circuit (all circuits other than the reference voltage generation circuit) 3 and a comparator 6 for comparing the reference voltage and the external terminal voltage. ing. In addition, an external power source 4 and an external terminal voltage supply source 5 for supplying power to the semiconductor device are shown on the outside of the semiconductor device 2. In Figure 3,
The reference voltage generation circuit 1 includes two voltage control resistors RI. R
2 and a smoothing capacitor C1, and the output voltage VC of the reference voltage generating circuit is a voltage given by. Here, Rl and R2 are generally set to sufficiently high resistance values (several tens of kilohms or more) for purposes such as suppressing standby power supply current. This makes it susceptible to noise due to capacitive coupling with other signals within the semiconductor device, and in order to smooth this out, a smoothing capacitor C! is placed between the reference voltage output and the power supply. will be inserted. (C+ is a value that is sufficiently large compared to the stray capacitance between the reference voltage generation circuit output node and the signal line.) In the above explanation, the resistor R. ．． R
Although the resistor division method according to No. 2 has been exemplified, a transistor (for example, a depletion type MOS transistor with the gate and source shorted) may be used instead of the resistor, or a resistor and a transistor connected in parallel may be used. Good too.

Problems to be Solved by the Invention In the conventional system as described above, the output voltage Vc of the reference voltage generation circuit is directly affected by fluctuations in the power supply voltage. That is, as shown in FIG. 3, between the positive terminal VCC-EX of the external power supply 4 and the power supply terminal VCC of the semiconductor device in which the reference voltage generation circuit is incorporated, there is a resistance of the power supply wiring external to the semiconductor device. , packaging wiring resistance,
There is an equivalent resistance 10 composed of bonding wires, wiring resistance within the semiconductor device, and the like. Furthermore, in reality, the influence of wiring inductance cannot be ignored, and is considered to be more important than resistance. Similarly, V SS-EX and V
An equivalent resistance Rl1 also exists between SS. Furthermore, since a current flows through the internal circuit 3 during operation of the semiconductor device, the equivalent resistance Rho on the VCC side. Vss{tlII
A current I3 shown in FIG. 3 flows through the equivalent resistance Rl1.

A schematic diagram of this current waveform is shown in FIG. Note that the current flowing through the reference voltage generation circuit is R, . Since R2 has a sufficiently high resistance, it was ignored. As a result, the power supply node VCC of the semiconductor device. VSS is equal to each equivalent resistance RIG. Due to the voltage drop at the Rth point, a waveform as shown in FIG. 4 is obtained. Here, if the operating cycle of the semiconductor device is sufficiently short compared to the time constant determined by CI and R1 or CI and R2 of the reference voltage generation circuit, the reference voltage Vc is
It will be subject to noise due to capacitive coupling with VSS via. And a V like VEXT in Figure 3
If this vc is used as a comparison voltage for determining whether the external voltage is high or low based on SS-EXT, an erroneous determination will occur.

In this way, conventional reference voltage generation circuits are directly affected by power supply fluctuations through the smoothing capacitor used to reduce noise from the signal line, and as a result, they are far from being able to reduce noise. There was a problem with it being put away.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, and aims to provide a reference voltage generation circuit equipped with a smoothing circuit that can simultaneously greatly reduce noise from a power supply and other signal lines.

Means for Solving the Problems The present invention provides a first power source with a constant potential, a second power source with a constant potential, and a voltage that generates and outputs an arbitrary potential between the first and second power sources. a control circuit; and a voltage smoothing circuit for smoothing the output voltage of the voltage control circuit, the voltage smoothing circuit having a capacitor connected at both ends to the output of the voltage control circuit and the first power source; is a reference voltage generation circuit constituted by the output of the voltage control circuit and a capacitor connected to the second power supply.

Effect of the Invention According to the present invention, it is possible to simultaneously reduce noise from the power supply and other signal lines in a reference voltage generation circuit incorporated in a semiconductor device to a negligible level, thereby creating a stable reference voltage generation circuit. It will be provided.

Embodiment FIG. 1 shows a reference voltage generation circuit according to an embodiment of the present invention incorporated into a semiconductor device, and FIG. 2 schematically shows operating waveforms of main nodes in the circuit of FIG. It shows.

In the conventional reference voltage generation circuit shown in FIG. 3, the voltage smoothing circuit part was composed only of the capacitor C1 inserted between the output Vc and VSS of the voltage control circuit. In the reference voltage generating circuit shown in FIG. 1, the voltage smoothing circuit portion is composed of a capacitor C1 between the outputs VC and VSS of the voltage control circuit, and a capacitor C2 between Vc and VCC.

Considering the case where the equivalent resistances RIG and Rl1 in FIG. 1 have the same value, the equivalent resistance RIG. Rll voltage drop 01
, 7J2 (see FIG. 2) have the same value, so it is clear that by setting the capacitors CI and 02 to have the same capacity, the influence of power supply fluctuations on VC can be completely canceled out. In addition, each equivalent resistance RIO. Even if the resistance value of Rl+ is different, CI/C2=RIO/RII= l U+ l/l02
A similar effect can be obtained by determining the capacitance values of cl and c2 according to the relationship l-=■. Also, at this time, C. ，
If c2 is set to a sufficiently large value, capacitive couple noise from other signal lines to Vc can also be made negligible.

As described above, according to this embodiment, capacitor C1 and 0
By setting the value of 2 to an appropriate value, the influence of power supply fluctuations on the reference voltage VC can be canceled, and at the same time, noise from other signal lines can be greatly reduced. In reality, in addition to the components of the equivalent resistances RIO and Rl+, inductance components are naturally included, and the line impedance is equal to the equivalent resistance RIO. There are many cases that cannot be expressed in a simplified form such as Rl+. In such a case, for example, the second
By actually measuring the values of 7JI and 02 in the figure,
2) CI. What is necessary is to determine the capacitance value of C2.

Effects of the Invention The reference voltage generation circuit of the present invention has a voltage smoothing circuit portion that is connected between the output voltage VC of the voltage control circuit and one power supply terminal voltage VCC, and between VC and the other power supply terminal voltage Vc.
By inserting a smoothing capacitor between each c,
This cancels out the effect of power supply fluctuations due to voltage drops in the power supply line on the output voltage VC, and as a result, even when incorporated into a semiconductor device, stable and low-noise reference voltage generation can be easily achieved, resulting in high performance. It is possible to obtain a quasi-voltage generating circuit which has a great practical effect.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a reference voltage generation circuit according to an embodiment of the present invention, FIG. 2 is a schematic diagram of waveforms at each node in FIG. 1 of the reference voltage generation circuit according to an embodiment of the present invention, and FIG. FIG. 4 is a schematic diagram of waveforms at each node of the conventional example of the reference voltage generation circuit shown in FIG. 3. VCC-EXT+ VSS-EXT. Vl! XT.
vcc, vss """ power supply node, Rl, R2,
RIO, Rth...Resistance, C+/C2...
... Capacitor, II. I2. 13...
...Current value, U,,02...Voltage value, Vc...
...Circuit output node. Name of agent: Patent attorney Toshio Nakao and one other person Figure 1 Figure 2 6
-p dofu

Claims (1)

[Claims] A first power supply with a constant potential, a second power supply with a constant potential, a voltage control circuit that generates and outputs an arbitrary potential between the first and second power supplies, and an output voltage of the voltage control circuit. a voltage smoothing circuit for smoothing, the voltage smoothing circuit having both ends connected to the output of the voltage control circuit and the first power supply, and having both ends connected to the output of the voltage control circuit and the second power supply. A reference voltage generation circuit comprising a capacitor connected to a power supply.