JP3595933B2 - Reference signal creation circuit - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a reference signal creation circuit that creates an input signal for smoothing an input signal with an integration circuit including a resistor and a capacitor and comparing the input signal with the integration signal.
[0002]
[Prior art]
In general, as a process of an analog input signal in a control circuit of an electric device or the like, as shown in FIG. 1, the input signal Vin is smoothed by an integrating circuit 1 including a resistor R and a capacitor C to create a reference signal Vref, A process is generally performed in which the DC component is cut by extracting the reference signal component from the original input signal by the amplifier 2 to extract the output signal Vo having only the AC component.
[0003]
Also, for example, in a rotation sensor configured to detect a rotation state of a magnetized balance weight at a certain angle or more by a hall element provided on a fixed side, as shown in FIG. Is used as an input signal Vin, the input signal Vin is smoothed by an integrating circuit 1 composed of a resistor R and a capacitor C to create a reference signal Vref, and the input signal Vin is input to the operational amplifier 2 using the reference signal Vref as a threshold value. By comparing the output signal Vo with the reference signal Vref, an output signal Vo binarized to a high level “H” and a low level “L” is extracted.
[0004]
FIG. 2 shows an analog input signal Vin and a reference signal Vref (a DC component of the input signal Vin) obtained by smoothing the analog input signal Vin with the integration circuit 1. When the reference signal Vref is a threshold for binarization, a portion of the input signal Vin exceeding the reference signal Vref is output as an "H" level, and a portion below the reference signal Vref is output as an "L" level. become.
[0005]
In such a circuit configuration, as shown in FIG. 1, when an electrode 3 is provided around a resistor R in an integrating circuit 1 and a leakage current il from the peripheral electrode 3 acts on the resistor R, Since the resistance R has a relatively large resistance value (for example, about 200 KΩ), as shown in FIG. 3, the reference signal Vref ′ becomes the level of the original reference signal Vref according to (il × R). As a result, an error occurs in cutting or binarization of the DC component of the input signal Vin.
[0006]
Conventionally, however, the resistor R is provided separately from the peripheral electrode so as not to be affected by the leakage current from the peripheral electrode.
[0007]
[Problems to be solved by the invention]
The problem to be solved is that when an input signal is smoothed by an integrating circuit composed of a resistor and a capacitor to create a reference signal for comparison with the input signal, the reference signal is not affected by leakage current from peripheral electrodes. If the resistor R is provided at a distance from the peripheral electrode, the degree of freedom in circuit design is reduced, and the chip size is increased especially when an IC is to be implemented.
[0008]
[Means for Solving the Problems]
The reference signal generating circuit according to the present invention is affected by a leakage current from a nearby peripheral electrode when the input signal is smoothed by an integrating circuit including a resistor and a capacitor to generate a reference signal for comparison with the input signal. The resistance is surrounded by a shield ring that holds the level of the input signal so that there is no resistance.
[0009]
【Example】
As shown in FIG. 4, the reference signal generation circuit according to the present invention generates a reference signal Vref by smoothing an analog input signal Vin with an integrating circuit 1 including a resistor R and a capacitor C. The reference signal Vref is compared with the created reference signal Vref to obtain an output signal Vo from which the DC component has been cut or a binarized output signal Vo using the reference signal Vref as a threshold value. The resistance R in the circuit 1 is electrically connected to the input line so as to be surrounded by the shield ring 4 held at the level of the input signal Vd.
[0010]
Therefore, the leakage current il from the peripheral electrode 3 is prevented by the shield ring 4, and the integration circuit 1 can always generate a stable reference signal Vref without being affected by the leakage current il.
[0011]
At this time, even if the potential of the shield ring 4 fluctuates due to the leakage current il, since the shield ring 4 itself is connected to the signal line of the input signal Vin, the level of the input signal Vin changes with the potential fluctuation of the shield ring 4. Since the reference signal Vref fluctuates and the reference signal Vref is generated based on the reference signal Vref, a reference signal Vref of a constant level is always obtained.
[0012]
FIG. 5 shows a case where the reference signal generation circuit according to the present invention is formed on a semiconductor substrate 5 in the form of an IC. Here, a shield ring 4 is formed around the resistor R formed by the active layer, and a leakage current il from the peripheral electrode 3 formed on the same semiconductor substrate 5 is blocked by the shield ring 4 so that the internal The resistance R is not reached.
[0013]
【The invention's effect】
As described above, the present invention is a reference signal generation circuit for generating a reference signal for smoothing an input signal by an integration circuit including a resistor and a capacitor and comparing the input signal with the input signal, wherein the resistance is held at the level of the input signal. It is surrounded by a shield ring, so it is not affected by leakage current from nearby peripheral electrodes, and can always create a stable reference signal.It is necessary to set the resistance away from the peripheral electrodes This has the advantage that the degree of freedom in circuit design is improved, and the chip size can be reduced, especially in the case of IC implementation.
[Brief description of the drawings]
FIG. 1 is an electric circuit diagram showing a general circuit configuration for comparing an input signal with a reference signal created by smoothing an input signal by an integrating circuit including a resistor and a capacitor.
FIG. 2 is a diagram illustrating an example of an input signal and a reference signal obtained by smoothing the input signal by an integration circuit;
FIG. 3 is a diagram illustrating an example of an input signal when a leakage current from a peripheral electrode acts on a resistance of an integration circuit and a reference signal obtained by smoothing the input signal by the integration circuit;
FIG. 4 is an electric circuit diagram showing a configuration example when the present invention is implemented in the circuit configuration of FIG. 1;
FIG. 5 is a front sectional view of a shield ring portion in a case where a reference signal generation circuit according to the present invention is formed as an IC on a semiconductor substrate.
[Explanation of symbols]
Reference Signs List 1 integration circuit 2 operational amplifier 3 peripheral electrode 4 shield ring 5 semiconductor substrate

Claims (3)

In a reference signal creating circuit for creating a reference signal for comparing an input signal with an input signal by smoothing the input signal with an integrating circuit including a resistor and a capacitor, the resistor is surrounded by a shield ring holding the level of the input signal. A reference signal generating circuit. 2. The reference signal generation circuit according to claim 1, wherein the reference signal is for cutting off a DC component in the input signal and extracting only an AC component in comparison with the input signal. 2. The reference signal generation circuit according to claim 1, wherein the reference signal is used for binarizing the input signal in comparison with the input signal.

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